bluuebunny/crossref_metadata_2025 huggingface dataset:
On wavelets interpolated from a pair of wavelet sets
Authors: Rzeszotnik Ziemowit , Speegle Darrin
Published: March 2003

We show that any wavelet, with the support of its Fourier transform small enough, can be interpolated from a pair of wavelet sets. In particular, the support of the Fourier transform of such wavelets must contain a wavelet set, answering a special case of an open problem of Larson. The interpolation procedure, which was introduced by X. Dai and D. Larson, allows us also to prove the extension property.
On locally finite 𝑝-groups satisfying an Engel condition
Authors: Abdollahi Alireza , Traustason Gunnar
Published: March 2003

For a given positive integer

n
n

and a given prime number

p
p

, let

r
=
r
(
n
,
p
)

r=r(n,p)

be the integer satisfying

p

r
−
1

>
n
≤

p

r

p^{r-1}>n\leq p^{r}

. We show that every locally finite

p
p

-group, satisfying the

n
n

-Engel identity, is (nilpotent of

n
n

-bounded class)-by-(finite exponent) where the best upper bound for the exponent is either

p

r

p^{r}

or

p

r
−
1

p^{r-1}

if

p
p

is odd. When

p
=
2

p=2

the best upper bound is

p

r
−
1

,

p

r

p^{r-1},p^{r}

or

p

r
+
1

p^{r+1}

. In the second part of the paper we focus our attention on

4
4

-Engel groups. With the aid of the results of the first part we show that every

4
4

-Engel

3
3

-group is soluble and the derived length is bounded by some constant.
Triples of arrangements and local systems
Authors: Cohen Daniel
Published: March 2003

For a triple of complex hyperplane arrangements, there is a well-known long exact sequence relating the cohomology of the complements. We observe that this result extends to certain local coefficient systems, and use this extension to study the characteristic varieties of arrangements. We show that the first characteristic variety may contain components that are translated by characters of any order, thereby answering a question of A. Suciu.
Admissible vectors for the regular representation
Authors: Führ Hartmut
Published: March 2003

It is well known that for irreducible, square-integrable representations of a locally compact group, there exist so-called admissible vectors which allow the construction of generalized continuous wavelet transforms. In this paper we discuss when the irreducibility requirement can be dropped, using a connection between generalized wavelet transforms and Plancherel theory. For unimodular groups with type I regular representation, the existence of admissible vectors is equivalent to a finite measure condition. The main result of this paper states that this restriction disappears in the nonunimodular case: Given a nondiscrete, second countable group

G
G

with type I regular representation

λ
G

\lambda _G

, we show that

λ
G

\lambda _G

itself (and hence every subrepresentation thereof) has an admissible vector in the sense of wavelet theory iff

G
G

is nonunimodular.
𝐺-coincidences for maps of homotopy spheres into CW-complexes
Authors: Gonçalves Daciberg , Jaworowski Jan , Pergher Pedro
Published: March 2003

Let

G
G

be a finite group acting freely in a CW-complex

Σ

m

\Sigma ^{m}

which is a homotopy

m
m

-dimensional sphere and let

f
:

Σ

m

→
Y

f:\Sigma ^{m} \to Y

be a map of

Σ

m

\Sigma ^{m}

to a finite

k
k

-dimensional CW-complex

Y
Y

. We show that if

m
≥
|
G
|
k

m\geq \vert G\vert k

, then

f
f

has an

(
H
,
G
)

(H,G)

-coincidence for some nontrivial subgroup

H
H

of

G
G

.
Convexity numbers of closed sets in ℝⁿ
Authors: Geschke Stefan , Kojman Menachem
Published: March 2003

For

n
>
2

n>2

let

I

n

\mathcal I_n

be the

σ
\sigma

-ideal in

P

(

n
ω

)

\mathcal P(n^\omega )

generated by all sets which do not contain

n
n

equidistant points in the usual metric on

n
ω

n^\omega

. For each

n
>
2

n>2

a set

S
n

S_n

is constructed in

R

n

\mathbb {R}^n

so that the

σ
\sigma

-ideal which is generated by the convex subsets of

S
n

S_n

restricted to the convexity radical

K
(

S
n

)

K(S_n)

is isomorphic to

I

n

\mathcal I_n

. Thus

cov
⁡
(

I

n

)

\operatorname {cov}(\mathcal I_n)

is equal to the least number of convex subsets required to cover

S
n

S_n

— the convexity number of

S
n

S_n

. For every non-increasing function

f
:
ω
∖
2
→
{
κ
∈
card
:
cf
⁡
(
κ
)
>

ℵ
0

}

f:\omega \setminus 2\to \{\kappa \in \operatorname {card}:\operatorname {cf}(\kappa )>\aleph _0\}

we construct a model of set theory in which

cov
⁡
(

I

n

)
=
f
(
n
)

\operatorname {cov}(\mathcal I_n)=f(n)

for each

n
∈
ω
∖
2

n\in \omega \setminus 2

. When

f
f

is strictly decreasing up to

n
n

,

n
−
1

n-1

uncountable cardinals are simultaneously realized as convexity numbers of closed subsets of

R

n

\mathbb {R}^n

. It is conjectured that

n
n

, but never more than

n
n

, different uncountable cardinals can occur simultaneously as convexity numbers of closed subsets of

R

n

\mathbb {R}^n

. This conjecture is true for

n
=
1

n=1

and

n
=
2

n=2

.
Any 3-manifold 1-dominates at most finitely many 3-manifolds of 𝑆³-geometry
Authors: Hayat-Legrand Claude , Wang Shicheng , Zieschang Heiner
Published: March 2003

Any 3-manifold 1-dominates at most finitely many 3-manifolds supporting

S
3

S^3

geometry.
A priori estimates for higher order multipliers on a circle
Authors: Himonas A. , Misiołek Gerard
Published: March 2003

We present an elementary proof of an a priori estimate of Bourgain for a general class of multipliers on a circle using an extension of methods developed in our previous work. The main tool is a suitable version of a counting argument of Zygmund for unbounded regions.
Normal bases for Hopf-Galois algebras
Authors: Kreimer H.
Published: March 2003

Let

H
H

be a Hopf algebra over a commutative ring

R
R

such that

H
H

is a finitely generated, projective module over

R
R

, let

A
A

be a right

H
H

-comodule algebra, and let

B
B

be the subalgebra of

H
H

-coinvariant elements of

A
A

. If

A
A

is a Galois extension of

B
B

and

B
B

is a local subalgebra of the center of

A
A

, then

A
A

is a cleft right

H
H

-comodule algebra or, equivalently, there is a normal basis for

A
A

over

B
B

.
Stabilization of evolution equations by noise
Authors: Kwiecińska Anna
Published: March 2003

We consider a deterministic equation of evolution
\[

X
′

(
t
)
=
A
X
(
t
)
d
t
,

X’(t)=AX(t)dt,

\]
in a separable, real Hilbert space. We prove that if

A
A

generates a

C
0

C_0

-semigroup, then this equation can be stabilized, in terms of Lyapunov exponents, by noise.
Self-commutator inequalities in higher dimension
Authors: Martin Mircea
Published: March 2003

Three natural multi-dimensional substitutes for the self-commutator of a Hilbert space operator are introduced and generalizations of Putnam’s inequality to tuples of operators with semidefinite self-commutators are indicated. In addition, a Riesz transform model is developed and investigated.
Ergodicity of the action of the positive rationals on the group of finite adeles and the Bost-Connes phase transition theorem
Authors: Neshveyev Sergey
Published: March 2003

We study relatively invariant measures with the multiplicators

Q

+
∗

∋
q
↦

q

−
β

{\mathbb Q}^*_+\ni q\mapsto q^{-\beta }

on the space

A

f

\mathcal A_f

of finite adeles. We prove that for

β
∈
(
0
,
1
]

\beta \in (0,1]

such measures are ergodic, and then deduce from this the uniqueness of KMS

β

_\beta

-states for the Bost-Connes system. Combining this with a result of Blackadar and Boca-Zaharescu, we also obtain ergodicity of the action of

Q

∗

\mathbb Q^*

on the full adeles.
Excesses, duality gaps and weak compactness
Authors: Simons Stephen
Published: March 2003

We explore the connection between the concepts “excess” and “duality gap” from epigraphical analysis and optimization, and the functional analytic concepts of weak* and weak compactness. We also discuss briefly the connection with R. C. James’s “sup theorem”.
A proof of a partition theorem for [ℚ]ⁿ
Authors: Vuksanovic Vojkan
Published: March 2003

In this note we give a proof of Devlin’s theorem via Milliken’s theorem about weakly embedded subtrees of the complete binary tree

2

>

N

2^{>\mathbb N }

. Unlike the original proof which is (still unpublished) long and uses the language of category theory, our proof is short and uses direct combinatorial reasoning.
An example of amenable Kac systems
Authors: Ng Chi-Keung
Published: March 2003

By giving an interesting characterisation of amenable multiplicative unitaries, we show, in a very simple way, that bicrossproducts of amenable locally compact groups are both amenable and coamenable.
Finite sums of commutators
Authors: Pop Ciprian
Published: March 2003

We show that elements of unital

C
∗

C^*

-algebras without tracial states are finite sums of commutators. Moreover, the number of commutators involved is bounded, depending only on the given

C
∗

C^*

-algebra.
Induction formula for the Artin conductors of mod ℓ Galois representations
Authors: Taguchi Yuichiro
Published: March 2003

A formula is given to describe how the Artin conductor of a mod

ℓ
\ell

Galois representation behaves with respect to induction of the representation.
On the complexity of the description of *-algebra representations by unbounded operators
Authors: Turowska Lyudmila
Published: March 2003

We study the complexity of the problem to describe, up to unitary equivalence, representations of

∗
*

-algebras by unbounded operators on a Hilbert space. A number of examples are developed in detail.
Asymptotics of Sobolev embeddings and singular perturbations for the 𝑝-Laplacian
Authors: del Pino Manuel , Flores César
Published: March 2003

We consider the best constant

S
(

Ω
λ

)

S(\Omega _\lambda )

for the embedding of

W

1
,
p

(

Ω
λ

)

W^{1,p} (\Omega _\lambda )

into

L
q

(

Ω
λ

)

L^q(\Omega _\lambda )

where

1
>
p
>
2

1>p>2

,

p
>
q
>

N
p

N
−
p

p>q> {Np\over N-p}

. Here

Ω
λ

=
λ
Ω

\Omega _\lambda = \lambda \Omega

with

Ω
\Omega

a smooth, bounded domain in

R

n

\mathbb {R}^n

and

λ
\lambda

a large positive number. It is proven by the validity of the expansion
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper S left-parenthesis normal upper Omega Subscript lamda Baseline right-parenthesis equals upper S left-parenthesis double-struck upper R Subscript plus Superscript n Baseline right-parenthesis minus lamda Superscript negative 1 Baseline gamma max Underscript x element-of partial-differential normal upper Omega Endscripts upper H left-parenthesis x right-parenthesis plus o left-parenthesis lamda Superscript negative 1 Baseline right-parenthesis comma">

S
(

Ω
λ

)
=
S
(

R

+
n

)
−

λ

−
1

γ

max

x
∈
∂
Ω

H
(
x
)
+
o
(

λ

−
1

)
,

\begin{equation} S( \Omega _\lambda ) = S(\mathbb {R}^n_+) - \lambda ^{-1} \gamma \max _{x\in \partial \Omega } H(x) + o ( \lambda ^{-1} ), \nonumber \end{equation}

as

λ
→
∞

\lambda \to \infty

, where

γ
\gamma

is a positive constant depending on

p
,
q

p,q

and

N
N

. The behavior of associated extremals, which satisfy an equation involving the

p
p

-Laplacian operator, is also analyzed.
Applications of a theorem of H. Cramér to the Selberg class
Authors: Kaczorowski J. , Perelli A.
Published: March 2003

We prove two results on the nature of the Dirichlet coefficients

a
(
n
)

a(n)

of the

L
L

-functions in the extended Selberg class

S

♯

\mathcal {S}^\sharp

. The first result asserts that if

a
(
n
)
=
ϕ
(
log
⁡
n
)

a(n)=\phi (\log n)

for some entire function

ϕ
(
z
)

\phi (z)

of order 1 and finite type, then

ϕ
(
z
)

\phi (z)

is constant. The second result states, roughly, that if

a
(
n
)
ϕ
(
log
⁡
n
)

a(n)\phi (\log n)

are still the coefficients of some

L
L

-function from

S

♯

\mathcal {S}^\sharp

, then

ϕ
(
z
)
=
c

e

i
β
z

\phi (z)=ce^{i\beta z}

with

c
∈

C

c\in \mathbb {C}

and

β
∈

R

\beta \in \mathbb {R}

. The proofs are based on an old result by Cramér and on the characterization of the functions of degree 1 of

S

♯

\mathcal {S}^\sharp

.
New identities of differential operators from orbital integrals on 𝐺𝐿(𝑟,𝐂)
Authors: Mezo Paul
Published: March 2003

We derive identities of differential operators on complex general linear groups which appear in the differential equations satisfied by weighted orbital integrals. These identities stem from and have applications to comparisons of metaplectic coverings.
Helgason-Marchaud inversion formulas for Radon transforms
Authors: Rubin Boris
Published: March 2003

Let

X
X

be either the hyperbolic space

H

n

\mathbb {H} ^{n}

or the unit sphere

S

n

S^{n}

, and let

Ξ
\Xi

be the set of all

k
k

-dimensional totally geodesic submanifolds of

X
,

1
≤
k
≤
n
−
1

X, \, 1 \le k \le n-1

. For

x
∈
X

x \in X

and

ξ
∈
Ξ

\xi \in \Xi

, the totally geodesic Radon transform

f
(
x
)
→

f
^

(
ξ
)

f(x) \to \hat f(\xi )

is studied. By averaging

f
^

(
ξ
)

\hat f(\xi )

over all

ξ
\xi

at a distance

θ
\theta

from

x
x

, and applying Riemann-Liouville fractional differentiation in

θ
\theta

, S. Helgason has recovered

f
(
x
)

f(x)

. We show that in the hyperbolic case this method blows up if

f
f

does not decrease sufficiently fast. The situation can be saved if one employs Marchaud’s fractional derivatives instead of the Riemann-Liouville ones. New inversion formulas for

f
^

(
ξ
)
,

f
∈

L

p

(
X
)

\hat f(\xi ), \, f \in L^{p}(X)

, are obtained.
Geometric characterizations of some classes of operators in C*-algebras and von Neumann algebras
Authors: Akemann Charles , Weaver Nik
Published: March 2003

We present geometric characterizations of the partial isometries, unitaries, and invertible operators in C*-algebras and von Neumann algebras.
A generalization of Lomonosov’s inequality and its applications to invariant subspaces
Authors: Ansari Shamim
Published: March 2003

In this article we generalize Victor Lomonosov’s famous inequality so as to be applicable to a wider class of functions. Then using it we prove that the adjoint of an algebra with a compactness property which is weaker than the PS property, employed by Victor Lomonosov, has nontrivial invariant subspaces.
Lawlessness and rank restrictions in certain finitary groups
Authors: Pinnock C.
Published: March 2003

We give two applications of the recent classification of locally finite simple finitary skew linear groups. We show that certain irreducible finitary skew linear groups of infinite dimension generate the variety of all groups and have infinite Prüfer rank.
𝐿^{𝑝} boundedness of localization operators associated to left regular representations
Authors: Wong M.
Published: March 2003

We prove an

L
p

L^p

boundedness result for localization operators associated to left regular representations of locally compact and Hausdorff groups and give an application to wavelet multipliers.
Construction of orthonormal wavelets using Kampé de Fériet functions
Authors: Zayed Ahmed
Published: March 2003

One of the main aims of this paper is to bridge the gap between two branches of mathematics, special functions and wavelets. This is done by showing how special functions can be used to construct orthonormal wavelet bases in a multiresolution analysis setting. The construction uses hypergeometric functions of one and two variables and a generalization of the latter, known as Kampé de Fériet functions. The mother wavelets constructed by this process are entire functions given by rapidly converging power series that allow easy and fast numerical evaluation. Explicit representation of wavelets facilitates, among other things, the study of the analytic properties of wavelets.
A Covering Theorem with applications
Authors: Neugebauer C.
Published: March 2003

We prove a Covering Theorem that allows us to prove modified norm inequalities for general maximal operators. We will also give applications to convergence of a sequence of linear operators and the differentiation of the integral.
Making light of mathematics
Authors: Berry Michael
Published: March 2003

Summary of AMS Gibbs Lecture, delivered at San Diego, CA, 6 January 2002.
Patterns in eigenvalues: the 70th Josiah Willard Gibbs lecture
Authors: Diaconis Persi
Published: March 2003

Typical large unitary matrices show remarkable patterns in their eigenvalue distribution. These same patterns appear in telephone encryption, the zeros of Riemann’s zeta function, a variety of physics problems, and in the study of Toeplitz operators. This paper surveys these applications and what is currently known about the patterns.
Logical dreams
Authors: Shelah Saharon
Published: March 2003

We discuss the past and future of set theory, axiom systems and independence results. We deal in particular with cardinal arithmetic.
A Cluster of Genes Encodes the Two Types of Chalcone Isomerase Involved in the Biosynthesis of General Flavonoids and Legume-Specific 5-Deoxy(iso)flavonoids in Lotus japonicus
Authors: Shimada Norimoto , Aoki Toshio , Sato Shusei , Nakamura Yasukazu , Tabata Satoshi , Ayabe Shin-ichi
Published: March 2003

Leguminous plants produce 5-deoxyflavonoids and 5-deoxyisoflavonoids that play essential roles in legume-microbe interactions. Together with chalcone polyketide reductase and cytochrome P450 2-hydroxyisoflavanone synthase, the chalcone isomerase (CHI) of leguminous plants is fundamental in the construction of these ecophysiologically active flavonoids. Although CHIs of nonleguminous plants isomerize only 6′-hydroxychalcone to 5-hydroxyflavanone (CHIs with this function are referred to as type I), leguminous CHIs convert both 6′-deoxychalcone and 6′-hydroxychalcone to 5-deoxyflavanone and 5-hydroxyflavanone, respectively (referred to as type II). In this study, we isolated multiple CHI cDNAs (cCHI1–cCHI3) from a model legume,Lotus japonicus. In contrast to previous observations, the amino acid sequence of CHI2 was highly homologous to nonleguminous CHIs, whereas CHI1 and CHI3 were the conventional leguminous type. Furthermore, genome sequence analysis revealed that fourCHI genes (CHI1–3 and a putative gene, CHI4) form a tandem cluster within 15 kb. Biochemical analysis with recombinant CHIs expressed inEscherichia coli confirmed that CHI1 and CHI3 are type II CHIs and that CHI2 is a type I CHI. The occurrence of both types of CHIs is probably common in leguminous plants, and it was suggested that type II CHIs evolved from an ancestral CHI by gene duplication and began to produce 5-deoxy(iso)flavonoids along with the establishment of the Fabaceae.
Nod Factor Elicits Two Separable Calcium Responses inMedicago truncatula Root Hair Cells
Authors: Shaw Sidney L. , Long Sharon R.
Published: March 2003

Modulation of intracellular calcium levels plays a key role in the transduction of many biological signals. Here, we characterize early calcium responses of wild-type and mutant Medicago truncatula plants to nodulation factors produced by the bacterial symbiont Sinorhizobium meliloti using a dual-dye ratiometric imaging technique. When presented with 1 nm Nod factor, root hair cells exhibited only the previously described calcium spiking response initiating 10 min after application. Nod factor (10 nm) elicited an immediate increase in calcium levels that was temporally earlier and spatially distinct from calcium spikes occurring later in the same cell. Nod factor analogs that were structurally related, applied at 10 nm, failed to initiate this calcium flux response. Cells induced to spike with low Nod factor concentrations show a calcium flux response when Nod factor is raised from 1 to 10 nm. Plant mutants previously shown to be deficient for the calcium spiking response (dmi1 and dmi2) exhibited an immediate, truncated calcium flux with 10 nm Nod factor, demonstrating a competence to respond to Nod factor but an impaired ability to generate a full biphasic response. These results demonstrate that the legume root hair cell exhibits two independent calcium responses to Nod factor triggered at different agonist concentrations and suggests an early branch point in the Nod factor signal transduction pathway.
Expression of an Expansin Gene Is Correlated with Root Elongation in Soybean
Authors: Lee Dong-Keun , Ahn Ji Hoon , Song Sang-Kee , Choi Yang Do , Lee Jong Seob
Published: March 2003

Expansin is a family of proteins that catalyze long-term expansion of cell walls and has been considered a principal protein that affects cell expansion in plants. We have identified the first root-specific expansin gene in soybean (Glycine max),GmEXP1, which may be responsible for root elongation. Expression levels of GmEXP1 were very high in the roots of 1- to 5-d-old seedlings, in which rapid root elongation takes place. Furthermore, GmEXP1 mRNA was most abundant in the root tip region, where cell elongation occurs, but scarce in the region of maturation, where cell elongation ceases, implying that its expression is closely related to root development processes. In situ hybridization showed that GmEXP1 transcripts were preferentially present in the epidermal cells and underlying cell layers in the root tip of the primary and secondary roots. Ectopic expression ofGmEXP1 accelerated the root growth of transgenic tobacco (Nicotiana tabacum) seedlings, and the roots showed insensitivity to obstacle-touching stress. These results imply that theGmEXP1 gene plays an important role in root development in soybean, especially in the elongation and/or initiation of the primary and secondary roots.
The Arabidopsis Mutant alh1 Illustrates a Cross Talk between Ethylene and Auxin
Authors: Vandenbussche Filip , Smalle Jan , Le Jie , Saibo Nelson José Madeira , De Paepe Annelies , Chaerle Laury , Tietz Olaf , Smets Raphael , Laarhoven Lucas J.J. , Harren Frans J.M. , Van Onckelen Harry , Palme Klaus , Verbelen Jean-Pierre , Van Der Straeten Dominique
Published: March 2003

Ethylene or its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) can stimulate hypocotyl elongation in light-grown Arabidopsis seedlings. A mutant, designated ACC-related long hypocotyl 1 (alh1), that displayed a long hypocotyl in the light in the absence of the hormone was characterized. Etiolatedalh1 seedlings overproduced ethylene and had an exaggerated apical hook and a thicker hypocotyl, although no difference in hypocotyl length was observed when compared with wild type.Alh1 plants were less sensitive to ethylene, as reflected by reduction of ACC-mediated inhibition of hypocotyl growth in the dark and delay in flowering and leaf senescence.Alh1 also had an altered response to auxin, whereas auxin levels in whole alh1 seedlings remained unaffected. In contrast to wild type, alh1 seedlings showed a limited hypocotyl elongation when treated with indole-3-acetic acid. Alh1 roots had a faster response to gravity. Furthermore, the hypocotyl elongation of alh1 and of ACC-treated wild type was reverted by auxin transport inhibitors. In addition, auxin up-regulated genes were ectopically expressed in hypocotyls upon ACC treatment, suggesting that the ethylene response is mediated by auxins. Together, these data indicate thatalh1 is altered in the cross talk between ethylene and auxins, probably at the level of auxin transport.
4-Coumarate:Coenzyme A Ligase Has the Catalytic Capacity to Synthesize and Reuse Various (Di)Adenosine Polyphosphates
Authors: Pietrowska-Borek Małgorzata , Stuible Hans-Peter , Kombrink Erich , Guranowski Andrzej
Published: March 2003

4-Coumarate:coenzyme A ligase (4CL) is known to activate cinnamic acid derivatives to their corresponding coenzyme A esters. As a new type of 4CL-catalyzed reaction, we observed the synthesis of various mono- and diadenosine polyphosphates. Both the native 4CL2 isoform from Arabidopsis (At4CL2 wild type) and the At4CL2 gain of function mutant M293P/K320L, which exhibits the capacity to use a broader range of phenolic substrates, catalyzed the synthesis of adenosine 5′-tetraphosphate (p4A) and adenosine 5′-pentaphosphate when incubated with MgATP−2 and tripolyphosphate or tetrapolyphosphate (P4), respectively. Diadenosine 5′,5‴,-P1,P4-tetraphosphate represented the main product when the enzymes were supplied with only MgATP2−. The At4CL2 mutant M293P/K320L was studied in more detail and was also found to catalyze the synthesis of additional dinucleoside polyphosphates such as diadenosine 5′,5‴-P1,P5-pentaphosphate and dAp4dA from the appropriate substrates, p4A and dATP, respectively. Formation of Ap3A from ATP and ADP was not observed with either At4CL2 variant. In all cases analyzed, (di)adenosine polyphosphate synthesis was either strictly dependent on or strongly stimulated by the presence of a cognate cinnamic acid derivative. The At4CL2 mutant enzyme K540L carrying a point mutation in the catalytic center that is critical for adenylate intermediate formation was inactive in both p4A and diadenosine 5′,5‴,-P1,P4-tetraphosphate synthesis. These results indicate that the cinnamoyl-adenylate intermediate synthesized by At4CL2 not only functions as an intermediate in coenzyme A ester formation but can also act as a cocatalytic AMP-donor in (di)adenosine polyphosphate synthesis.
A Novel Cl− Inward-Rectifying Current in the Plasma Membrane of the Calcifying Marine Phytoplankton Coccolithus pelagicus
Authors: Taylor Alison R. , Brownlee Colin
Published: March 2003

We investigated the membrane properties and dominant ionic conductances in the plasma membrane of the calcifying marine phytoplankton Coccolithus pelagicus using the patch-clamp technique. Whole-cell recordings obtained from decalcified cells revealed a dominant anion conductance in response to membrane hyperpolarization. Ion substitution showed that the anion channels were selective for Cl− and Br− over other anions, and the sensitivity to the stilbene derivative 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid, ethacrynic acid, and Zn2+ revealed a pharmacological profile typical of many plant and animal anion channels. Voltage activation and kinetic characteristics of the C. pelagicusCl− channel are consistent with a novel function in plants as the inward rectifier that tightly regulates membrane potential. Membrane depolarization gave rise to nonselective cation currents and in some cases evoked action potential currents. We propose that these major ion conductances play an essential role in membrane voltage regulation that relates to the unique transport physiology of these calcifying phytoplankton.
A Diffusible Factor from Arbuscular Mycorrhizal Fungi Induces Symbiosis-Specific MtENOD11 Expression in Roots ofMedicago truncatula
Authors: Kosuta Sonja , Chabaud Mireille , Lougnon Géraldine , Gough Clare , Dénarié Jean , Barker David G. , Bécard Guillaume
Published: March 2003

Using dual cultures of arbuscular mycorrhizal (AM) fungi andMedicago truncatula separated by a physical barrier, we demonstrate that hyphae from germinating spores produce a diffusible factor that is perceived by roots in the absence of direct physical contact. This AM factor elicits expression of the Nod factor-inducible gene MtENOD11, visualized using a pMtENOD11-gusA reporter. Transgene induction occurs primarily in the root cortex, with expression stretching from the zone of root hair emergence to the region of mature root hairs. All AM fungi tested (Gigaspora rosea,Gigaspora gigantea, Gigaspora margarita, and Glomus intraradices) elicit a similar response, whereas pathogenic fungi such as Phythophthora medicaginis, Phoma medicaginis var pinodella andFusarium solani f.sp. phaseoli do not, suggesting that the observed root response is specific to AM fungi. Finally, pMtENOD11-gusA induction in response to the diffusible AM fungal factor is also observed with all threeM. truncatulaNod−/Myc− mutants (dmi1,dmi2, and dmi3), whereas the same mutants are blocked in their response to Nod factor. This positive response of the Nod−/Myc− mutants to the diffusible AM fungal factor and the different cellular localization of pMtENOD11-gusA expression in response to Nod factor versus AM factor suggest that signal transduction occurs via different pathways and that expression of MtENOD11 is differently regulated by the two diffusible factors.
Regulation of Root Elongation under Phosphorus Stress Involves Changes in Ethylene Responsiveness
Authors: Ma Zhong , Baskin Tobias I. , Brown Kathleen M. , Lynch Jonathan P.
Published: March 2003

We characterized the growth of the primary root of Arabidopsis under phosphorus sufficiency (1 mm phosphate) and deficiency (1 μm phosphate), focusing on the role of ethylene. We quantified the spatial profile of relative elongation with a novel method based on image processing, as well as the production rates of cortical cells, trichoblasts, and atrichoblasts. Phosphorus deficiency moderately decreased the maximal rate of relative elongation, shortened the growth zone, and decreased the production rate of both epidermal cell types but not of cortical cells. Inhibiting ethylene production (with aminoethoxyvinyl-glycine) or action (with 1-methylcyclopropene) increased elongation in high phosphorus and decreased it in low phosphorus. That these effects were specific to ethylene was confirmed by negating the effect of inhibited ethylene production with simultaneous treatment with an ethylene precursor (1-aminocyclopropane-1-carboxylic acid). Under both phosphorus regimes, ethylene regulated the maximal rate of relative elongation rather than the size of the growth zone. In addition, inhibiting ethylene action in high versus low phosphorus elicited opposite responses for the position of root hair initiation and for the production rates of cortex cells and atrichoblasts. We conclude that the root system acclimates to phosphorus deficiency by changing the signal transduction pathway connecting ethylene levels to growth and division.
Genetic Diversity of Eurycoma longifolia Inferred from Single Nucleotide Polymorphisms,
Authors: Osman Asiah , Jordan Barbara , Lessard Philip A. , Muhammad Norwati , Haron M. Rosli , Riffin Norifiza Mat , Sinskey Anthony J. , Rha ChoKyun , Housman David E.
Published: March 2003

Eurycoma longifolia Jack. is a treelet that grows in the forests of Southeast Asia and is widely used throughout the region because of its reported medicinal properties. Widespread harvesting of wild-grown trees has led to rapid thinning of natural populations, causing a potential decrease in genetic diversity amongE. longifolia. Suitable genetic markers would be very useful for propagation and breeding programs to support conservation of this species, although no such markers currently exist. To meet this need, we have applied a genome complexity reduction strategy to identify a series of single nucleotide polymorphisms (SNPs) within the genomes of several E.longifolia accessions. We have found that the occurrence of these SNPs reflects the geographic origins of individual plants and can distinguish different natural populations. This work demonstrates the rapid development of molecular genetic markers in species for which little or no genomic sequence information is available. The SNP markers that we have developed in this study will also be useful for identifying genetic fingerprints that correlate with other properties of E. longifolia, such as high regenerability or the appearance of bioactive metabolites.
Root Factors Induce Mitochondrial-Related Gene Expression and Fungal Respiration during the Developmental Switch from Asymbiosis to Presymbiosis in the Arbuscular Mycorrhizal FungusGigaspora rosea
Authors: Tamasloukht M'Barek , Séjalon-Delmas Nathalie , Kluever Astrid , Jauneau Alain , Roux Christophe , Bécard Guillaume , Franken Philipp
Published: March 2003

During spore germination, arbuscular mycorrhizal (AM) fungi show limited hyphal development in the absence of a host plant (asymbiotic). In the presence of root exudates, they switch to a new developmental stage (presymbiotic) characterized by extensive hyphal branching. Presymbiotic branching of the AM fungus Gigaspora rosea was induced in liquid medium by a semipurified exudate fraction from carrot (Daucus carota) root organ cultures. Changes in RNA accumulation patterns were monitored by differential display analysis. Differentially appearing cDNA fragments were cloned and further analyzed. Five cDNA fragments could be identified that show induced RNA accumulation 1 h after the addition of root exudate. Sequence similarities of two fragments to mammalian Nco4 and mitochondrial rRNA genes suggested that root exudates could influence fungal respiratory activity. To support this hypothesis, additional putative mitochondrial related-genes were shown to be induced by root exudates. These genes were identified after subtractive hybridization and putatively encode a pyruvate carboxylase and a mitochondrial ADP/ATP translocase. The geneGrosPyc1 for the pyruvate carboxylase was studied in more detail by cloning a cDNA and by quantifying its RNA accumulation. The hypothesis that respiratory activity of AM fungi is stimulated by root exudates was confirmed by physiological and cytological analyses in G. rosea and Glomus intraradices. Oxygen consumption and reducing activity of both fungi was induced after 3 and 2 h of exposition with the root factor, respectively, and the first respiration activation was detected in G. intraradices after approximately 90 min. In addition, changes in mitochondrial morphology, orientation, and overall biomass were detected in G. rosea after 4 h. In summary, the root-exuded factor rapidly induces the expression of certain fungal genes and, in turn, fungal respiratory activity before intense branching. This defines the developmental switch from asymbiosis to presymbiosis, first by gene activation (0.5–1 h), subsequently on the physiological level (1.5–3 h), and finally as a morphological response (after 5 h).
Analysis of the Small GTPase Gene Superfamily of Arabidopsis
Authors: Vernoud Vanessa , Horton Amy C. , Yang Zhenbiao , Nielsen Erik
Published: March 2003

Small GTP-binding proteins regulate diverse processes in eukaryotic cells such as signal transduction, cell proliferation, cytoskeletal organization, and intracellular membrane trafficking. These proteins function as molecular switches that cycle between “active” and “inactive” states, and this cycle is linked to the binding and hydrolysis of GTP. The Arabidopsis genome contains 93 genes that encode small GTP-binding protein homologs. Phylogenetic analysis of these genes shows that plants contain Rab, Rho, Arf, and Ran GTPases, but no Ras GTPases. We have assembled complete lists of these small GTPases families, as well as accessory proteins that control their activity, and review what is known of the functions of individual members of these families in Arabidopsis. We also discuss the possible roles of these GTPases in relation to their similarity to orthologs with known functions and localizations in yeast and/or animal systems.
The Role of Biotin in Regulating 3-Methylcrotonyl-Coenzyme A Carboxylase Expression in Arabidopsis
Authors: Che Ping , Weaver Lisa M. , Wurtele Eve Syrkin , Nikolau Basil J.
Published: March 2003

As a catalytic cofactor, biotin has a critical role in the enzymological mechanism of a number of enzymes that are essential in both catabolic and anabolic metabolic processes. In this study we demonstrate that biotin has additional non-catalytic functions in regulating gene expression in plants, which are biotin autotrophic organisms. Biotin controls expression of the biotin-containing enzyme, methylcrotonyl-coenzyme A (CoA) carboxylase by modulating the transcriptional, translational and/or posttranslational regulation of the expression of this enzyme. The bio1 mutant of Arabidopsis, which is blocked in the de novo biosynthesis of biotin, was used to experimentally alter the biotin status of this organism. In response to the bio1-associated depletion of biotin, the normally biotinylated A-subunit of methylcrotonyl-CoA carboxylase (MCCase) accumulates in its inactive apo-form, and both MCCase subunits hyperaccumulate. This hyperaccumulation occurs because the translation of each subunit mRNA is enhanced and/or because the each protein subunit becomes more stable. In addition, biotin affects the accumulation of distinct charge isoforms of MCCase. In contrast, in response to metabolic signals arising from the alteration in the carbon status of the organism, biotin modulates the transcription of the MCCase genes. These experiments reveal that in addition to its catalytic role as an enzyme cofactor, biotin has multiple roles in regulating gene expression.
Biphasic Superoxide Generation in Potato Tubers. A Self-Amplifying Response to Stress
Authors: Johnson S.M. , Doherty S.J. , Croy R.R.D.
Published: March 2003

Potato (Solanum tuberosum) cultivars differ quantitatively in their responses to mechanical stress including the ability to synthesize melanin pigments in tuber tissues. Investigations into the cellular events induced by mechanical stress on tuber tissues have shown that an early cellular response is a significant and rapid synthesis of superoxide radicals. This burst of radical production distinctively displays a reproducible biphasic pattern over time with peaks of generation at 2 and 5 h. A concomitant consequence of the generation of these free radicals is elevated levels of oxidatively modified tuber proteins. Both radical generation and protein modification vary between cultivars but both are directly proportional to the amount of melanin pigments produced. Cell-free extracts of mechanically stressed tissues, pectic fragments, and scission products generated from cell walls are able to induce superoxide generation in non-stressed tissues, indicating the participation of a biologically active factor that induces a further a phase of radical synthesis.
Regulation of the Alternative Oxidase Aox1 Gene inChlamydomonas reinhardtii. Role of the Nitrogen Source on the Expression of a Reporter Gene under the Control of theAox1 Promoter
Authors: Baurain Denis , Dinant Monique , Coosemans Nadine , Matagne René F.
Published: March 2003

In higher plants, various developmental and environmental conditions enhance expression of the alternative oxidase (AOX), whereas its induction in fungi is mainly dependent on cytochrome pathway restriction and triggering by reactive oxygen species. The AOX of the unicellular green alga Chlamydomonas reinhardtii is encoded by two different genes, the Aox1 gene being much more transcribed than Aox2. To analyze the transcriptional regulation of Aox1, we have fused its 1.4-kb promoter region to the promoterless arylsulfatase (Ars) reporter gene and measured ARS enzyme activities in transformants carrying the chimeric construct. We show that theAox1 promoter is generally unresponsive to a number of known AOX inducers, including stress agents, respiratory inhibitors, and metabolites, possibly because the AOX activity is constitutively high in the alga. In contrast, the Aox1 expression is strongly dependent on the nitrogen source, being down-regulated by ammonium and stimulated by nitrate. Inactivation of nitrate reductase leads to a further increase of expression. The stimulation by nitrate also occurs at the AOX protein and respiratory levels. A deletion analysis of the Aox1 promoter region demonstrates that a short upstream segment (−253 to +59 with respect to the transcription start site) is sufficient to ensure gene expression and regulation, but that distal elements are required for full gene expression. The observed pattern of AOX regulation points to the possible interaction between chloroplast and mitochondria in relation to a potential increase of photogenerated ATP when nitrate is used as a nitrogen source.
Plasma Membrane H+-ATPase Is Involved in Auxin-Mediated Cell Elongation during Wheat Embryo Development
Authors: Rober-Kleber Nicole , Albrechtová Jolana T.P. , Fleig Sonja , Huck Norbert , Michalke Wolfgang , Wagner Edgar , Speth Volker , Neuhaus Gunther , Fischer-Iglesias Christiane
Published: March 2003

Previous investigations suggested that specific auxin spatial distribution due to auxin movements to particular embryonic regions was important for normal embryonic pattern formation. To gain information on the molecular mechanism(s) by which auxin acts to direct pattern formation in specific embryonic regions, the role of a plasma membrane (PM) ATPase was evaluated as downstream target of auxin in the present study. Western-blot analysis revealed that the PM H+-ATPase expression level was significantly increased by auxin in wheat (Triticum aestivum) embryos (two–three times increase). In bilaterally symmetrical embryos, the spatial expression pattern of the PM H+-ATPase correlates with the distribution pattern of the auxin analog, tritiated 5-azidoindole-3-acetic acid. A strong immunosignal was observed in the abaxial epidermis of the scutellum and in the epidermal cells at the distal tip of this organ. Pseudoratiometric analysis using a fluorescent pH indicator showed that the pH in the apoplast of the cells expressing the PM H+-ATPase was in average more acidic than the apoplastic pH of nonexpressing cells. Cellulose staining of living embryos revealed that cells of the scutellum abaxial epidermis expressing the ATPase were longer than the scutellum adaxial epidermal cells, where the protein was not expressed. Our data indicate that auxin activates the proton pump resulting in apoplastic acidification, a process contributing to cell wall loosening and elongation of the scutellum. Therefore, we suggest that the PM H+-ATPase is a component of the auxin-signaling cascade that may direct pattern formation in embryos.
Auxin Signaling in Arabidopsis Leaf Vascular Development
Authors: Mattsson Jim , Ckurshumova Wenzislava , Berleth Thomas
Published: March 2003

A number of observations have implicated auxin in the formation of vascular tissues in plant organs. These include vascular strand formation in response to local auxin application, the effects of impaired auxin transport on vascular patterns and suggestive phenotypes of Arabidopsis auxin response mutants. In this study, we have used molecular markers to visualize auxin response patterns in developing Arabidopsis leaves as well as Arabidopsis mutants and transgenic plants to trace pathways of auxin signal transduction controlling the expression of early procambial genes. We show that in young Arabidopsis leaf primordia, molecular auxin response patterns presage sites of procambial differentiation. This is the case not only in normal development but also upon experimental manipulation of auxin transport suggesting that local auxin signals are instrumental in patterning Arabidopsis leaf vasculature. We further found that the activity of the Arabidopsis gene MONOPTEROS, which is required for proper vascular differentiation, is also essential in a spectrum of auxin responses, which include the regulation of rapidly auxin-inducible AUX/IAA genes, and discovered the tissue-specific vascular expression profile of the class I homeodomain-leucine zipper gene, AtHB20. Interestingly, MONOPTEROSactivity is a limiting factor in the expression of AtHB8and AtHB20, two genes encoding transcriptional regulators expressed early in procambial development. Our observations connect general auxin signaling with early controls of vascular differentiation and suggest molecular mechanisms for auxin signaling in patterned cell differentiation.
Phytochromes A and B Mediate Red-Light-Induced Positive Phototropism in Roots
Authors: Kiss John Z. , Mullen Jack L. , Correll Melanie J. , Hangarter Roger P.
Published: March 2003

The interaction of tropisms is important in determining the final growth form of the plant body. In roots, gravitropism is the predominant tropistic response, but phototropism also plays a role in the oriented growth of roots in flowering plants. In blue or white light, roots exhibit negative phototropism that is mediated by the phototropin family of photoreceptors. In contrast, red light induces a positive phototropism in Arabidopsis roots. Because this red-light-induced response is weak relative to both gravitropism and negative phototropism, we used a novel device to study phototropism without the complications of a counteracting gravitational stimulus. This device is based on a computer-controlled system using real-time image analysis of root growth and a feedback-regulated rotatable stage. Our data show that this system is useful to study root phototropism in response to red light, because in wild-type roots, the maximal curvature detected with this apparatus is 30° to 40°, compared with 5° to 10° without the feedback system. In positive root phototropism, sensing of red light occurs in the root itself and is not dependent on shoot-derived signals resulting from light perception.Phytochrome (Phy)A andphyB were severely impaired in red-light-induced phototropism, whereas the phyD and phyEmutants were normal in this response. Thus, PHYA and PHYB play a key role in mediating red-light-dependent positive phototropism in roots. Although phytochrome has been shown to mediate phototropism in some lower plant groups, this is one of the few reports indicating a phytochrome-dependent phototropism in flowering plants.
Enhanced Gravitropism of Roots with a Disrupted Cap Actin Cytoskeleton
Authors: Hou Guichuan , Mohamalawari Deepti R. , Blancaflor Elison B.
Published: March 2003

The actin cytoskeleton has been proposed to be a major player in plant gravitropism. However, understanding the role of actin in this process is far from complete. To address this problem, we conducted an analysis of the effect of Latrunculin B (Lat B), a potent actin-disrupting drug, on root gravitropism using various parameters that included detailed curvature kinetics, estimation of gravitropic sensitivity, and monitoring of curvature development after extended clinorotation. Lat B treatment resulted in a promotion of root curvature after a 90° reorientation in three plant species tested. More significantly, the sensitivity of maize (Zea mays) roots to gravity was enhanced after actin disruption, as determined from a comparison of presentation time of Lat B-treated versus untreated roots. A short 10-min gravistimulus followed by extended rotation on a 1-rpm clinostat resulted in extensive gravitropic responses, manifested as curvature that often exceeded 90°. Application of Lat B to the cap or elongation zone of maize roots resulted in the disruption of the actin cytoskeleton, which was confined to the area of localized Lat B application. Only roots with Lat B applied to the cap displayed the strong curvature responses after extended clinorotation. Our study demonstrates that disrupting the actin cytoskeleton in the cap leads to the persistence of a signal established by a previous gravistimulus. Therefore, actin could function in root gravitropism by providing a mechanism to regulate the proliferation of a gravitropic signal originating from the cap to allow the root to attain its correct orientation or set point angle.