bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the free boundary of a quasivariational inequality arising in a problem of quality control
Authors: Friedman Avner 
Published: July 2010

In some recent work in stochastic optimization with partial observation occurring in quality control problems, Anderson and Friedman [1], [2] have shown that the optimal cost can be determined as a solution of the quasi variational inequality
\[

M
w

(
p
)

+

f

(
p
)

≥

0
,

w

(
p
)

≤

ψ

(

p
;

w

)

,

(

M
w

(
p
)

+

f

(
p
)

)

(

w

(
p
)

−

ψ

(

p
;

w

)

)

=

0

\begin {gathered} Mw\left ( p \right )\, + \,f\left ( p \right )\, \geq \,0,\,w\left ( p \right )\, \leq \,\psi \left ( {p;\,w} \right ), \left ( {Mw\left ( p \right )\, + \,f\left ( p \right )} \right )\left ( {w\left ( p \right )\, - \,\psi \left ( {p;\,w} \right )} \right )\, = \,0 \end {gathered}

\]
in the simplex

p
i

>

0

{p_i}\, > \,0

,

∑

i

=

1

n

p
i

=

1

\sum \nolimits _{i\, = \,1}^n {{p_i}\, = \,1}

. Here f,

ψ
\psi

are given functions of p,

ψ
\psi

is a functional of w, and M is a given elliptic operator degenerating on the boundary. This system has a unique solution when M does not degenerate in the interior of the simplex. The aim of this paper is to study the free boundary, that is, the boundary of the set where

w

(
p
)

>

ψ

(

p
;

w

)

w\left ( p \right )\, > \,\psi \left ( {p;\,w} \right )

.
On modular functions in characteristic 𝑝
Authors: Li Wen Ch’ing Winnie 
Published: July 2010

Let

k

=

F

q

(
T
)

k\, = \,{{\textbf {F}}_q}\left ( T \right )

be a function field of one variable over a finite field

F

q

{{\textbf {F}}_q}

. For a nonzero polynomial

A

∈

F

q

[
T
]

A\, \in \,{{\textbf {F}}_q}\left [ T \right ]

one can define the modular group

Γ

(
A
)

\Gamma \left ( A \right )

. In this paper, we continue a theme introduced by Weil, and study the

λ
\lambda

-harmonic modular functions for

Γ

(
A
)

\Gamma \left ( A \right )

. The main purpose of this paper is to give a natural definition of

λ
\lambda

-harmonic Eisenstein series for

Γ

(
A
)

\Gamma \left ( A \right )

so that we obtain a decomposition theory of

λ
\lambda

-harmonic modular functions, analogous to the classical results of Hecke. That is, we prove
\[

Modular

Function

=

Eisenstein

series

⊕

Cusp Functions

.

{\text {Modular}}\,{\text {Function}}\,{\text { = }}\,{\text {Eisenstein}}\,{\text {series}}\, \oplus \,{\text {Cusp Functions}}{\text {.}}

\]
Moreover, the dimension of the space generated by

λ
\lambda

-harmonic Eisenstein series for

Γ

(
A
)

\Gamma \left ( A \right )

is equal to the number of cusps of

Γ

(
A
)

\Gamma \left ( A \right )

, and so is independent of

λ
\lambda

. For the definition of

λ
\lambda

-harmonic Eisenstein series and the proof of decomposition theory, we consider two cases: (i)

λ

≠

±
2

q

\lambda \, \ne \, \pm 2\sqrt q

and (ii)

λ

=

±
2

q

\lambda \, = \, \pm 2\sqrt q

, separately. Case (i) is treated in the usual way. Case (ii), being a “degenerate” case, is more interesting and requires more complicated analysis.
Orthogonal polynomials defined by a recurrence relation
Authors: Nevai Paul G. 
Published: July 2010

R. Askey has conjectured that if a system of orthogonal polynomials is defined by the three term recurrence relation
\[

x

p

n

−

1

(
x
)

=

γ

n

−

1

γ

n

p
n

(
x
)

+

α

n

−

1

p

n

−

1

(
x
)

+

γ

n

−

2

γ

n

−

1

p

n

−

2

(
x
)

x{p_{n\, - \,1}}\left ( x \right )\, = \,\frac {{{\gamma _{n\, - \,1}}}} {{{\gamma _{n\,}}}}\,{p_n}\left ( x \right )\, + \,{\alpha _{n\, - \,1}}{p_{n\, - \,1}}\left ( x \right )\, + \,\frac {{{\gamma _{n\, - \,2}}}} {{{\gamma _{n\, - \,1}}}}\,{p_{n\, - \,2}}\left ( x \right )

\]
and
\[

α
n

=

(
−
1
)

n

n

const

+

O

(

1

n
2

)

,

{\alpha _n}\, = \,\frac {{{{( - 1)}^n}}} {n}\,{\text {const}}\,{\text { + }}O\left ( {\frac {1} {{{n^2}}}} \right ),

\]

\[

γ
n

γ

n
+
1

=

1
2

+

(
−
1
)

n

n

const

+

O

(

1

n
2

)

,

\frac {{{\gamma _n}}} {{{\gamma _{n + 1}}}}\, = \,\frac {1} {2}\, + \,\frac {{{{( - 1)}^n}}} {n}\,{\text {const}}\,{\text { + }}O\left ( {\frac {1} {{{n^2}}}} \right ),

\]
then the logarithm of the absolutely continuous portion of the corresponding weight function is integrable. The purpose of this paper is to prove R. Askey’s conjecture and solve related problems.
Uniformly continuous functionals on the Fourier algebra of any locally compact group
Authors: Lau Anthony To Ming 
Published: July 2010

Let

G
G

be any locally compact group. Let

V
N
(
G
)

VN(G)

be the von Neumann algebra generated by the left regular representation of

G
G

. We study in this paper the closed subspace

U
B
C
(

G
^

)

UBC(\hat {G})

of

V
N
(
G
)

VN(G)

consisting of the uniformly continuous functionals as defined by E. Granirer. When

G
G

is abelian,

U
B
C
(

G
^

)

UBC(\hat {G})

is precisely the bounded uniformly continuous functions on the dual group

G
^

\hat {G}

. We prove among other things that if

G
G

is amenable, then the Banach algebra

U
B
C
(

G
^

)
∗

UBC(\hat {G})^\ast

(with the Arens product) contains a copy of the Fourier-Stieltjes algebra in its centre. Furthermore,

U
B
C
(

G
^

)
∗

UBC(\hat {G})^\ast

is commutative if and only if

G
G

is discrete. We characterize

W
(

G
^

)

W(\hat {G})

, the weakly almost periodic functionals, as the largest subspace

X
X

of

V
N
(
G
)

VN(G)

for which the Arens product makes sense on

X
∗

X^*

and

X
∗

X^*

is commutative. We also show that if

G
G

is amenable, then for certain subspaces

Y
Y

of

V
N
(
G
)

VN(G)

which are invariant under the action of the Fourier algebra

A
(
G
)

A(G)

, the algebra of bounded linear operators on

Y
Y

commuting with the action of

A
(
G
)

A(G)

is isometric and algebra isomorphic to

X
∗

X^*

for some

X
⊆
U
B
C
(

G
^

)

X \subseteq UBC(\hat {G})

.
Complete characterization of functions which act, via superposition, on Sobolev spaces
Authors: Marcus Moshe , Mizel Victor J. 
Published: July 2010

Given a domain

Ω
⊂

R
N

\Omega \subset {R_N}

and a Borel function

h
:

R
m

→
R

h:\,{R_m} \to R

, conditions on h are sought ensuring that for every m-tuple of functions

u
i

{u_i}

belonging to the first order Sobolev space

W

1
,
p

(
Ω
)

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

, the function

h
(

u
1

(
⋅
)
,
…
,

u
m

(
⋅
)
)

h({u_1}( \cdot ), \ldots ,{u_m}( \cdot ))

will belong to a first order Sobolev space

W

1
,
r

(
Ω
)

{W^{1,r}}(\Omega )

,

1
⩽
r
⩽
p
>
∞

1 \leqslant r \leqslant p > \infty

.In this paper conditions are found which are both necessary and sufficient in order that h have the above property. This result is based on a characterization obtained here for those Borel functions

g
:

R
m

×

(

R
N

)
m

→
R

g:\,{R_m} \times {({R_N})_m} \to R

satisfying the requirement that for every m-tuple of functions

u
i

∈

W

1
,
p

(
Ω
)

{u_i} \in {W^{1,p}}(\Omega )

the function

g
(

u
1

(
⋅
)
,
…
,

u
m

(
⋅
)
,
∇

u
1

(
⋅
)
,
…
,
∇

u
m

(
⋅
)
)

g({u_1}( \cdot ), \ldots ,{u_m}( \cdot ),\nabla {u_1}( \cdot ), \ldots ,\nabla {u_m}( \cdot ))

belongs to

L
r

(
Ω
)

{L^r}(\Omega )

. A needed result on the measurability of the set of

R
k

{R_k}

-Lebesgue points of a function on

R
N

{R_N}

is presented in an appendix.
On a sufficient condition for proximity
Authors: Lau Ka Sing 
Published: July 2010

A closed subspace M in a Banach space X is called U-proximinal if it satisfies:

(
1
+
ρ
)
S
∩
(
S
+
M
)
⊆
S
+
ε
(
ρ
)
(
S
∩
M
)

(1 + \rho )S \cap (S + M) \subseteq S + \varepsilon (\rho )(S \cap M)

, for some positive valued function

ε
(
ρ
)

\varepsilon (\rho )

,

ρ
>
0

\rho > 0

, and

ε
(
ρ
)
→
0

\varepsilon (\rho ) \to 0

as

ρ

→

0

\rho \, \to \, 0

, where S is the closed unit ball of X. One of the important properties of this class of subspaces is that the metric projections are continuous. We show that many interesting subspaces are U-proximinal, for example, the subspaces with the 2-ball property (semi M-ideals) and certain subspaces of compact operators in the spaces of bounded linear operators.
On an extremal property of Doob’s class
Authors: Hwang J. S. 
Published: July 2010

Recently, we have solved a long open problem of Doob (1935). To introduce the result proved here, we say that a function

f
(
z
)

f(z)

belongs to Doob’s class D, if

f
(
z
)

f(z)

is analytic in the unit disk U and has radial limit zero at an endpoint of some arc R on the unit circle such that

lim

inf

n
→
∞

|

f
(

P
n

)

|

\operatorname {lim} \,{\operatorname {inf} _{n \to \infty }}\,\left | {f({P_n})} \right |

, where

{

P
n

}

\{ {P_n}\}

is an arbitrary sequence of points in U tending to an arbitrary interior point of R. With this definition, our main result is the following extremal property of Doob’s class. Theorem.

inf

f
∈
D

‖
f
‖

=

2

/

e

{\operatorname {inf} _{f \in D}}\left \| f \right \|\, = \,{2 /e}

, where

‖
f
‖

=

sup

z
∈
U

(
1

−

|

z

|

2

)

|

f
′

(
z
)

|

\left \| f \right \|\, = \,{\sup _{z \in U}}(1\, - |z{|^2})|f’(z)|

.
The Dirichlet norm and the norm of Szegő type
Authors: Saitoh Saburou 
Published: July 2010

Let S be a smoothly bounded region in the complex plane. Let

g
(
z
,
t
)

g(z,t)

denote the Green’s function of S with pole at t. We show that
\[

∬
S

|

f
′

(
z
)

|

2

d
x

d
y

⩽

1
2

∫

∂
S

|

f
′

(
z
)

|

2

(

∂
g
(
z
,
t
)

∂

n
z

)

−
1

|

d
z

|

\iint _S {|f’(z){|^2}\,dx\,dy\, \leqslant \,\frac {1}{2}\int _{\partial S} {|f’(z){|^2}{{\left ( {\frac {{\partial g(z,t)}} {{\partial {n_z}}}} \right )}^{ - 1}}|dz|} }

\]
holds for any analytic function

f
(
z
)

f(z)

on

S

∪

∂
S

S\, \cup \,\partial S

. This curious inequality is obtained as a special case of a much more general result.
Necessary conditions for the convergence of cardinal Hermite splines as their degree tends to infinity
Authors: Goodman T. N. T. 
Published: July 2010

Let

S

n
,
s

{\mathcal {S}_{n,s}}

denote the class of cardinal Hermite splines of degree n having knots of multiplicity S at the integers. In this paper we show that if

f
n

→

f

{f_n}\, \to \,f

uniformly on R, where

f
n

∈

S

i

n
,
s

i
n

→

∞

{f_n}\, \in \,{\mathcal {S}_{{i_{n,s}}}}\,{i_n}\, \to \,\infty

as

n

→

∞

n\, \to \,\infty

, and f is bounded, then f is the restriction to R of an entire function of exponential type

⩽

S

\leqslant \,S

. In proving this result, we need to derive some extremal properties of certain splines

E

n
,
s

∈

S

n
,
s

{\mathcal {E}_{n,s}}\, \in \,{\mathcal {S}_{n,s}}

, in particular that

|

|

E

n
,
s

|

|

∞

||{\mathcal {E}_{n,s}}|{|_\infty }

minimises

|

|

S

|

|

∞

||S|{|_\infty }

over

S

∈

S

n
,
s

S\, \in \,{\mathcal {S}_{n,s}}

with

|

|

S

(
n
)

|

|

∞

=

|

|

E

n
,
s

(
n
)

|

|

∞

||{S^{(n)}}|{|_\infty }\, = \,||\mathcal {E}_{n,s}^{(n)}|{|_\infty }

.
First Report on the Occurrence of Grapevine leafroll-associated virus 5 in Chilean Grapevines
Authors: Engel E. A. , Escobar P. F. , Rivera P. A. , Valenzuela P. D. T. 
Published: July 2010

Grapevine leafroll is one of the most widespread and economically damaging viral diseases of grapevines. At least eight distinct Grapevine leafroll-associated viruses (GLRaVs), all members of the Closteroviridae family, have been associated with this disease (4). GLRaV-5 was recently reported in vineyards from Argentina (2). To determine if GLRaV-5 was present in Chilean grapevines, in addition to the previously reported GLRaV-1, -2, -3, -4, -7, and -9 (1), 45 dormant cane samples from 12 different cultivars were collected from different geographic regions of Chile and screened by reverse transcription-PCR. Two of the forty-five samples (cvs. Sauvignon Blanc and Superior) collected from the III (700 km north of Santiago) and VI (150 km south of Santiago) regions of Chile, respectively, were found to be infected with GLRaV-5 using two different pairs of virus-specific primers. The first pair of primers, LR5-1F: 5′-CCCGTGATACAAGGTAGGACA-3′ and LR5-1R: 5′-CAGACTTCACCTCCTGTTAC-3′ (3), was used to amplify a 690-bp fragment corresponding to a partial region of the coat protein gene. The sequences obtained from the two positive samples (GenBank Accession Nos. HM214148 and HM214149) shared 97 and 94% of nucleotide identities, respectively, with the corresponding fragment of a reference GLRaV-5 isolate (GenBank Accession No. EU815935). Both samples shared 99% of amino acid identity with the same reference isolate. A second pair of primers, LR5upF: 5′-CTCTGCTTTTCTGCTGGCA-3′ and LR5doR: 5′-TATCTTTTATCTCCCGATAAACGAG-3′ (4) that amplified a 160-bp fragment of the HSP70h gene was also used. The positive Chilean samples (GenBank Accession Nos. HM214150 and HM214151) shared in both cases 98% nucleotide and 98% amino acid identities with the corresponding fragment of a reference GLRaV-5 isolate (Accession No. AF039552). The two GLRaV-5-positive plants were additionally infected with other viruses previously reported in Chile (1). The cv. Sauvignon Blanc sample was also infected with GLRaV-2, Grapevine fleck virus, and Grapevine rupestris stem pitting-associated virus. The cv. Superior sample was also infected with GLRaV-3, GLRaV-4, and Grapevine virus A. References: (1) E. A. Engel et al. J. Virol. Methods 163:445, 2010. (2) S. Gomez et al. Virus Genes 38:184, 2009. (3) X. Good and J. Monis. Phytopathology 91:274, 2001. (4) V. I. Maliogka et al. J. Virol. Methods 154:41, 2008.
First Report of Fusarium andiyazi Associated with Rice Bakanae in Italy
Authors: Prà M. Dal , Tonti S. , Pancaldi D. , Nipoti P. , Alberti I. 
Published: July 2010

Rice (Oryza sativa L.) is cultivated on approximately 230,000 ha in northern Italy. Since 2001, increasing economical losses presumably caused by Fusarium fujikuroi Nirenberg (Gibberella fujikuroi mating population C), an exotic fungus known as the etiological agent of Bakanae disease, have been reported in Italy. The spread of this disease is primarily seedborne. In 2009, during an annual survey of Italian rice seed, 69 samples were tested for the presence of strains belonging to the G. fujikuroi species complex. Four hundred seeds per sample were surface sterilized and then placed in 90-mm Petri dishes containing potato dextrose agar and incubated for 7 days at 21°C. Thirty two putative G. fujikuroi strains were single-spore purified and identified on the basis of their morphological features on Spezieller Nährstoffarmer agar plates with a piece of sterile filter paper. Strains were characterized at species level by morphological observations (1,2) and translation elongation factor 1-α (TEF) gene sequencing. Unexpectedly, 60% of the strains evaluated belonged to the species F. andiyazi Marasas, Rheeder, Lampr., K.A. Zeller & J.F. Leslie. This fungus, first described on sorghum (Sorghum bicolor L.) in Africa and the United States (1), has been reported to be one of the species associated with Bakanae in Asia and Africa (3). Two F. andiyazi strains, (E432 and E439), isolated in the district of Modena were chosen for pathogenicity testing and their TEF gene sequences were deposited in GenBank (Accession Nos. GU827420 and GU827419). A conidial suspension was produced on Mung-bean liquid media and adjusted to a concentration of 1 × 106 CFU/ml. Italian cv. Galileo was used in the test because of its high susceptibility to Bakanae (Ente Nazionale delle Sementi Elette, Verona, Italy, data unpublished). Rice seeds were heat sterilized for 20 min at 60°C, submerged for 30 min in the conidial suspensions, dried, and subjected to a blotter test. Uninoculated, sterilized seeds served as a control. Seeds were incubated for 15 days in a growth chamber (26°C, 80% relative humidity, and 12-h photoperiod). For each strain, the experiment was repeated three times on samples of 25 seedlings. Results were analyzed by analysis of variance and Tukey test. Symptoms consisted of a generic seedling wilt, a root length reduction ranging from 21 to 48%, and the presence of root discoloration. Seed germination was reduced by 9%. Shoot development was not significantly altered. Proof of pathogenicity was obtained through reisolation of F. andiyazi from symptomatic tissues. To our knowledge, this is the first report of F. andiyazi on rice in Europe. References: (1) W. F. O. Marasas et al. Mycologia 93:1203, 2001. (2) H. I. Niremberg and K. O'Donnell. Mycologia 90:434, 1998. (3) E. G. Wulff et al. Environ. Microbiol. 12:649, 2009.
First Report of Cucumber mosaic virus Infecting Blephilia hirsuta in North America
Authors: Poudel B. , Laney A. G. , Tzanetakis I. E. 
Published: July 2010

Blephilia hirsuta (Pursh) Benth. var. hirsuta, an ornamental plant known as hairy pagoda or hairy wood mint (Lamiaceae), is native to eastern North America and is listed as an endangered species or a species of special concern in several northeastern states ( http://www.ct.gov/dep/cwp/view.asp?a=2702&q=323482&depNav_GID=1628 and http://www.mass.gov/dfwele/dfw/nhesp/species_info/mesa_list/mesa_list.htm ). B. hirsuta, grown as an ornamental on the University of Arkansas campus in Fayetteville, exhibited mottling symptoms indicative of viral infection. Double-stranded RNA extractions (3) yielded four bands of approximately 3.2, 2.9, 2.2, and 0.9 kb, a pattern identical to that of Cucumber mosaic virus (CMV [2]). Nicotiana benthamiana and Chenopodium quinoa seedlings were mechanically inoculated with sap from symptomatic tissue. N. benthamiana inoculated plants were stunted and developed systemic mosaic and C. quinoa inoculated plants developed local lesions, whereas mock inoculated plants remained symptomless. Dot-blot and indirect ELISA using antisera against CMV (developed by H. A Scott) gave strong reactions when testing symptomatic tissue from B. hirusta, N. benthamiana, and C. quinoa compared with no reaction for symptomless plants. Total nucleic acid extractions (4) from symptomatic tissue was subjected to reverse transcription-PCR using Cucumovirus degenerate primers (1). An amplicon of approximately 940 bases was obtained and sequenced. The sequence, deposited in GenBank under Accession No. GU453918, confirmed the results of the immunological assays that B. hirsuta was infected with CMV. The nucleotide identities between the B. hirsuta isolate and those of the Fny CMV group exceeded 98%. To our knowledge, this is the first report of CMV infecting B. hirsuta, not only in North America, but globally. This finding has major implications for the ornamental industry and the viability of the endangered species. Given the wide range of CMV, B. hirsuta may act as a reservoir for the virus and facilitate transmission to ornamentals and other plants. In addition, the virus may reduce host fitness and undermine the efforts to preserve the species in areas that is threatened. References: (1) S. K. Choi et al. J. Virol. Methods 83:67, 1999. (2) I. E. Tzanetakis. Plant Dis. 93:431, 2009. (3) I. E. Tzanetakis and R. R. Martin. J. Virol. Methods 149:167, 2008. (4) I. E. Tzanetakis et al. Virus Res. 127:26, 2007.
First Report of Powdery Mildew Caused by Leveillula taurica of Field-Grown Sweet Pepper in the Pacific Northwest
Authors: Glawe Dean A. , Barlow Tess , Eggers Jordan E. , Hamm Philip B. 
Published: July 2010

In August 2009, a grower reported a disease affecting nearly all plants in a drip-irrigated field of sweet pepper cv. Excalibur in Umatilla Co., OR. The fungus was determined to be Leveillula taurica (Lév.) G. Arnaud, previously unreported from this host in Oregon or from field-grown peppers in the Pacific Northwest. This report documents the taxonomic determination of this species and provides information about the disease outbreak, including economic impact. Accepted for publication 18 May 2010. Published 8 July 2010.
Integrating Planting Dates and Fungicide Applications for Managing White Mold of Dry Beans in Western Nebraska
Authors: Harveson Robert M. , Steadman James R. , Urrea Carlos A. 
Published: July 2010

White mold, caused by the soilborne fungus Sclerotinia sclerotiorum, is one of the most destructive diseases of common beans (Phaseolus vulgaris L.) and is greatly influenced by environmental conditions and certain agronomic practices. A 3-year study (2003 to 2005) evaluated planting date and thiophanate-methyl fungicide applications based on decision aids consisting of blue plate technique, sugar beet Cercospora leaf spot (CLS) disease forecasting model, and crop phenology (90% bloom). Overall yields were lower in 2003 and higher in 2005, and disease severity was greater in 2004. Planting dry beans in late June to early July resulted in higher levels of disease than planting in late May or mid-June in 2004. Late planting also resulted in lower yields and 100-seed weight in 2004 and 2005 than the early and mid-plantings. Compared to the control and CLS model, fungicide applications based on the blue plate and 90% bloom treatments reduced disease severity in 2004 and 2005, while also increasing 100-seed weight and yields in 2004. Accepted for publication 8 May 2010. Published 1 July 2010.
First Report of Charcoal Rot of Sunflower in Minnesota, USA
Authors: Gulya T. , Mengistu A. , Kinzer K. , Balbyshev N. , Markell S. 
Published: July 2010

Charcoal rot was first observed on sunflower in North and South Dakota in 1998, and was widespread on soybeans recently in Iowa, suggesting that Macrophomina may becoming more common in cooler growing areas of Midwestern United States. With the multitude of Macrophomina hosts in the northern Great Plains and the high incidence of microsclerotia we detected in soil, high disease potential may exist, suggesting that in drier, hotter years the sunflower crop may be affected by this disease. Accepted for publication 17 May 2010. Published 7 July 2010.
First Report in North America of Atypical Symptoms Caused by Colletotrichum coccodes on Field-Grown Potato Tubers During Storage
Authors: Griffiths Helen M. , Zitter Thomas A. , Loeffler Kent , Jong Walter S. De , Menasha Sandra 
Published: July 2010

Colletotrichum coccodes commonly causes blemish type symptoms on potato tubers. This is the first report in North America of natural infection of tubers by C. coccodes causing sunken lesions during storage. Accepted for publication 31 May 2010. Published 8 July 2010.
Arabidopsis Cockayne Syndrome A-Like Proteins 1A and 1B Form a Complex with CULLIN4 and Damage DNA Binding Protein 1A and Regulate the Response to UV Irradiation
Authors: Zhang Caiguo , Guo Huiping , Zhang Jun , Guo Guangqin , Schumaker Karen S. , Guo Yan 
Published: July 2010

Abstract
In plants, as in animals, DNA is constantly subject to chemical modification. UV-B irradiation is a major genotoxic agent and has significant effects on plant growth and development. Through forward genetic screening, we identified a UV-B–sensitive mutant (csaat1a-3) in Arabidopsis thaliana, in which expression of CSAat1A, encoding a Cockayne Syndrome A-like protein, is reduced due to insertion of a T-DNA in the promoter region. Arabidopsis lacking CSAat1A or its homolog CSAat1B is more sensitive to UV-B and the genotoxic drug methyl methanesulfonate and exhibits reduced transcription-coupled repair activity. Yeast two-hybrid analysis indicated that both CSAat1A and B interact with DDB1A (UV-Damage DNA Binding Protein1). Coimmunoprecipitation assays demonstrated that CSAat1A and B associate with the CULLIN4 (CUL4)-DDB1A complex in Arabidopsis. A split-yellow fluorescent protein assay showed that this interaction occurs in the nucleus, consistent with the idea that the CUL4-DDB1A-CSA complex functions as a nuclear E3 ubiquitin ligase. CSAat1A and B formed heterotetramers in Arabidopsis. Taken together, our data suggest that the plant CUL4-DDB1ACSAat1A and B complex represents a unique mechanism to promote ubiquitination of substrates in response to DNA damage.