bluuebunny/crossref_metadata_2025_split huggingface dataset:
Salicylic acid has a role in regulating gene expression during leaf senescence
Authors: Morris Karl , ‐Mackerness Soheila A. ‐H. , Page Tania , John C. Fred , Murphy Alex M. , Carr John P. , Buchanan‐Wollaston Vicky 
Published: March 2003

SummaryLeaf senescence is a complex process that is controlled by multiple developmental and environmental signals and is manifested by induced expression of a large number of different genes. In this paper we describe experiments that show, for the first time, that the salicylic acid (SA)‐signalling pathway has a role in the control of gene expression during developmental senescence. Arabidopsis plants defective in the SA‐signalling pathway (npr1 and pad4 mutants and NahG transgenic plants) were used to investigate senescence‐enhanced gene expression, and a number of genes showed altered expression patterns. Senescence‐induced expression of the cysteine protease gene SAG12, for example, was conditional on the presence of SA, together with another unidentified senescence‐specific factor. Changes in gene expression patterns were accompanied by a delayed yellowing and reduced necrosis in the mutant plants defective in SA‐signalling, suggesting a role for SA in the cell death that occurs at the final stage of senescence. We propose the presence of a minimum of three senescence‐enhanced signalling factors in senescing leaves, one of which is SA. We also suggest that a combination of signalling factors is required for the optimum expression of many genes during senescence.
Mutations in the WUSCHEL gene of Arabidopsis thaliana result in the development of shoots without juvenile leaves
Authors: Hamada Susumu , Onouchi Hitoshi , Tanaka Hirokazu , Kudo Mitsuko , Liu Yao‐Guang , Shibata Daisuke , Machida Chiyoko , Machida Yasunori 
Published: March 2003

SummaryThe vegetative growth of Arabidopsis thaliana can be divided into two phases. The transition from the juvenile (early) phase to the adult (later) phase is associated with changes in several morphological features of leaves, such as the shape of leaf blades, the number of trichomes and patterns of venation. In a screening of mutants with altered morphological identities of leaves, we found one which we named juvenile leafless and misshapen shoot apical meristem (jam). The mutation represented a new allele of the WUSCHEL (WUS) gene, and, in its presence, plants produced no juvenile leaves. Analysis of the morphology of mutant plants revealed that all the rosette leaves had characteristics of adult leaves. The formation of the first rosette leaf in the wus(jam) mutant was markedly delayed, and occurred at the almost same time as formation of the third or fourth leaf in wild‐type plants. In the wild‐type, these leaves correspond to the first adult leaves. Analysis by RT–PCR showed that transcripts of WUS accumulated in shoot apices and roots, but not in cotyledons and leaves. The present results suggest that the WUS gene controls the morphological traits of rosette leaves either directly or indirectly. In view of the predicted function of the WUS gene, namely maintenance of stem cells within the shoot apical meristem, we suggest that the lack of juvenile leaves in the mutant might have been caused by interruption of leaf initiation during the juvenile phase or by halting of an entire process of formation of juvenile leaves.
Identification of a MADS‐box gene, FLOWERING LOCUS M, that represses flowering
Authors: Scortecci Katia C. , Michaels Scott D. , Amasino Richard M. 
Published: March 2003

SummaryThe timing of flowering is important for the reproductive success of plants. Here we describe the identification and characterization of a new MADS‐box gene, FLOWERING LOCUS M (FLM), which is involved in the transition from vegetative to reproductive development. FLM is similar in amino‐acid sequence to FLC, another MADS‐box gene involved in flowering‐time control. flm mutants are early flowering in both inductive and non‐inductive photoperiods, and flowering time is sensitive to FLM dosage. FLM overexpression produces late‐flowering plants. Thus FLM acts as an inhibitor of flowering. FLM is expressed in areas of cell division such as root and shoot apical regions and leaf primordia.
The CENTROMERE1 (CEN1) region of Arabidopsis thaliana: architecture and functional impact of chromatin
Authors: Haupt Wolfgang , Fischer Thilo C. , Winderl Sabine , Fransz Paul , Torres‐Ruiz Ramón A. 
Published: March 2003

SummaryWe have analysed the centromere 1 (CEN1) of Arabidopsis thaliana by integration of genetic, sequence and fluorescence in situ hybridisation (FISH) data. CEN1 is considered to include the centromeric core and the flanking left and right pericentromeric regions, which are distinct parts by structural and/or functional properties. CEN1 pericentromeres are composed of different dispersed repetitive elements, sometimes interrupted by functional genes. In contrast the CEN1 core is more uniformly structured harbouring only two different repeats.The presented analysis reveals aspects concerning distribution and effects of the uniformly shaped heterochromatin, which covers all CEN1 regions. A lethal mutation tightly linked to CEN1 enabled us to measure recombination frequencies within the heterochromatin in detail. In the left pericentromere, the change from eu‐ to heterochromatin is accompanied by a gradual change in sequence composition but by an extreme change in recombination frequency (from normal to 53‐fold decrease) which takes place within a small region spanning 15 kb. Generally, heterochromatin is known to suppress recombination. However, the same analysis reveals that left and right pericentromere, though similar in sequence composition, differ markedly in suppression (53‐fold versus 10‐fold). The centromeric core exhibits at least 200‐fold if not complete suppression. We discuss whether differences in (fine) composition reflect quantitative and qualitative differences in binding sites for heterochromatin proteins and in turn render different functional properties. Based on the presented data we estimate the sizes of Arabidopsis centromeres. These are typical for regional centromeres of higher eukaryotes and range from 4.4 Mb (CEN1) to 3.55 Mb (CEN4).
1‐Deoxy‐d‐xylulose 5‐phosphate reductoisomerase and plastid isoprenoid biosynthesis during tomato fruit ripening
Authors: Rodríguez‐Concepción Manuel , Ahumada Iván , Diez‐Juez Ester , Sauret‐Güeto Susanna , Lois Luisa María , Gallego Francesca , Carretero‐Paulet Lorenzo , Campos Narciso , Boronat Albert 
Published: March 2003

SummaryThe recently discovered 2‐C‐methyl‐d‐erythritol 4‐phosphate (MEP) pathway for the biosynthesis of plastid isoprenoids (including carotenoids) is not fully elucidated yet despite its central importance for plant life. It is known, however, that the first reaction completely specific to the pathway is the conversion of 1‐deoxy‐d‐xylulose 5‐phosphate (DXP) into MEP by the enzyme DXP reductoisomerase (DXR). We have identified a tomato cDNA encoding a protein with homology to DXR and in vivo activity, and show that the levels of the corresponding DXR mRNA and encoded protein in fruit tissues are similar before and during the massive accumulation of carotenoids characteristic of fruit ripening. The results are consistent with a non‐limiting role of DXR, and support previous work proposing DXP synthase (DXS) as the first regulatory enzyme for plastid isoprenoid biosynthesis in tomato fruit. Inhibition of DXR activity by fosmidomycin showed that plastid isoprenoid biosynthesis is required for tomato fruit carotenogenesis but not for other ripening processes. In addition, dormancy was reduced in seeds from fosmidomycin‐treated fruit but not in seeds from the tomato yellow ripe mutant (defective in phytoene synthase‐1, PSY1), suggesting that the isoform PSY2 might channel the production of carotenoids for abscisic acid biosynthesis. Furthermore, the complete arrest of tomato seedling development using fosmidomycin confirms a key role of the MEP pathway in plant development.
The tomato Rme1 locus is required for Mi‐1‐mediated resistance to root‐knot nematodes and the potato aphid
Authors: De Ilarduya Oscar Martinez , Moore Ann E. , Kaloshian Isgouhi 
Published: March 2003

SummaryThe tomato Mi‐1 gene confers resistance against root‐knot nematodes (Meloidogyne spp.) and a biotype of the potato aphid (Macrosiphum euphorbiae). Four mutagenized Mi‐1/Mi‐1 tomato populations were generated and screened for altered root‐knot nematode resistance. Four independent mutants belonging to two phenotypic classes were isolated. One mutant was chosen for further analyzes; rme1 (for resistance to Meloidogyne) exhibited levels of infection comparable with those found on susceptible controls. Molecular and genetic data confirmed that rme1 has a single recessive mutation in a locus different from Mi‐1. Cross‐sections through galls formed by feeding nematodes on rme1 roots were identical to sections from galls of susceptible tomato roots. In addition to nematode susceptibility, infestation of rme1 plants with the potato aphid showed that this mutation also abolished aphid resistance. To determine whether Rme1 functions in a general disease‐resistance pathway, the response against Fusarium oxysporum f.sp. lycopersici race 2, mediated by the I‐2 resistance gene, was studied. Both rme1 and the wild type plants were equally resistant to the fungal pathogen. These results indicate that Rme1 does not play a general role in disease resistance but may be specific for Mi‐1‐mediated resistance.
Identification of a novel genetically controlled step in mycorrhizal colonization: plant resistance to infection by fungal spores but not extra‐radical hyphae
Authors: David‐Schwartz Rakefet , Badani Hana , Smadar Wininger , Levy Avraham A. , Galili Gad , Kapulnik Yoram 
Published: March 2003

SummaryVesicular arbuscular mycorrhizal fungi infect plants by means of both spores and vegetative hyphae at early stages of symbiosis. Using 2500 M2 fast‐neutron‐mutagenized seeds of the miniature tomato (Lycopersicon esculentum) cultivar, Micro‐Tom, we isolated a mutant, M161, that is able to resist colonization in the presence of Glomus intraradices spores. The myc– phenotype of the mutant was stable for nine generations, and found to segregate as a single Mendelian recessive locus. The mutant exhibited morphological and growth‐pattern characteristics similar to those of wild‐type plants. Alterations of light intensity and day/night temperatures did not eliminate the myc– characteristic. Resistance to mycorrhizal fungal infection and colonization was also evident following inoculation with the fungi Glomus mosseae and Gigaspora margarita. Normal colonization of M161 was evident when mutant plants were grown together with arbuscular mycorrhizal‐inoculated wild‐type plants in the same growth medium. During evaluation of the pre‐infection stages in the mutant rhizosphere, spore germination and appressoria formation of G. intraradices were lower by 45 and 70%, respectively, than the rates obtained with wild‐type plants. These results reveal a novel, genetically controlled step in the arbuscular mycorrhizal colonization process, governed by at least one gene, which significantly reduces key steps in pre‐mycorrhizal infection stages.
Regulation of plant water loss by manipulating the expression of phospholipase Dα
Authors: Sang Yongming , Zheng Suqin , Li Weiqi , Huang Bingru , Wang Xuemin 
Published: March 2003

SummaryPhospholipase D (PLD) has been implicated in various processes, including signal transduction, membrane trafficking, and membrane degradation. Multiple forms of PLD with distinct biochemical properties have been described in the cell. In Arabidopsis, PLDα and PLDγ, but not PLDβ, were detected in guard cells, and antisense suppression resulted in a specific loss of PLDα. The abrogation of PLDα rendered plants less sensitive to abscisic acid and impaired stomatal closure induced by water deficits. PLDα‐depleted plants exhibited accelerated transpirational water loss and a decreased ability to tolerate drought stress. Overexpression of PLDα enhanced the leaf's sensitivity to abscisic acid. These findings provide molecular and physiological evidence that PLDα plays a crucial role in regulating stomatal movement and plant‐water status.
The MADS‐box gene DEFH28 from Antirrhinum is involved in the regulation of floral meristem identity and fruit development
Authors: Müller Bettina M. , Saedler Heinz , Zachgo Sabine 
Published: March 2003

Summary DEFH28 is a novel MADS‐box gene from Antirrhinum majus. Phylogenetic reconstruction indicates that it belongs to the SQUA‐subfamily of MADS‐box genes. Based on its expression pattern and the phenotype of transgenic plants it is predicted that DEFH28 exerts a dual function during flower development, namely control of meristem identity and fruit development. Firstly, DEFH28 is expressed in the inflorescence apical meristem and might control, together with SQUAMOSA (SQUA), floral meristem identity in Antirrhinum. Also, DEFH28 is sufficient to switch inflorescence shoot meristem to a floral fate in transgenic Arabidopsis thaliana plants. Secondly, DEFH28 is expressed in carpel walls, where it may regulate carpel wall differentiation and fruit maturation. Support for this later role comes from overexpression of DEFH28 throughout the silique in transgenic Arabidopsis plants where it altered the identity of the replum and valve margin cells so that they adopted a valve cell identity. This late aspect of the DEFH28 function is identical to the FRUITFULL (FUL) function of Arabidopsis as demonstrated in gain‐of‐function plants. FUL, like DEFH28, belongs to the SQUA‐subfamily of MADS‐box genes. DEFH28 most likely represents the ortholog of FUL. Promoter analysis shows that the control mechanism conferring a carpel wall specific expression has been conserved between Antirrhinum and Arabidopsis during evolution. Although the overall flower development between Antirrhinum and Arabidopsis is very similar, their carpels mature into different types of fruits: capsules and siliques, respectively. Therefore, it is suggested that the role of DEFH28 in control of carpel wall differentiation reflects a conserved molecular mechanism integrated into two very different carpel developmental pathways.
Use of red fluorescent protein from Discosoma sp. (dsRED) as a reporter for plant gene expression
Authors: Jach Guido , Binot Elke , Frings Sabine , Luxa Kerstin , Schell Jeff 
Published: March 2003

SummaryThe suitability of the recently described red fluorescent protein dsRED from reef corals for use as a reporter in plant molecular biology was investigated. Based on the clone pDSRED (Clontech), plant expression vectors were constructed for constitutive dsRED expression in the cytosol, the endoplasmic reticulum and the vacuole. Fluorescence microscopy of tobacco BY2 suspension culture cells transiently expressing the plant vectors generated proved that cytosolic expression of the dsRED gives rise to readily detectable levels of red fluorescence, whereas expression in the ER was poor. Vacuolar dsRED expression did not result in any significant fluorescence. dsRED transgenic tobacco SR1 plants were generated to test the sensitivity of dsRED as a reporter in an autofluorescent background, and to identify the possible impact of the introduced fluorescent protein on morphogenesis, plant development and fertility. During the transformation and regeneration phase plants did not show any abnormalities, indicating that dsRED is not interfering with plant development and morphogenesis. Regenerated plants were analysed by PCR, Western blot and fluorescence microscopy for the presence and expression of the transferred genes. The filter sets chosen for fluorescence microscopy proved to be able to block the red chlorophyll fluorescence completely, allowing specific dsRED detection. Best expression levels were obtained with dsRED targeted to the cytosol or chloroplasts. ER‐targeted expression of dsRED also gave rise to readily detectable fluorescence levels, whereas vacuolar expression yielded no fluorescence. dsRED transgenic plant lines expressing the protein in the cytosol, ER or chloroplast proved to be fertile. Seed set and germination were normal, except that the seeds and seedlings maintained the red fluorescence phenotype.
Distinct cell‐specific expression patterns of early and late gibberellin biosynthetic genes during Arabidopsis seed germination
Authors: Yamaguchi Shinjiro , Kamiya Yuji , Sun Tai‐ping 
Published: March 2003

SummaryGibberellins (GAs) are biosynthesized through a complex pathway that involves several classes of enzymes. To predict sites of individual GA biosynthetic steps, we studied cell type‐specific expression of genes encoding early and late GA biosynthetic enzymes in germinating Arabidopsis seeds. We showed that expression of two genes, AtGA3ox1 and AtGA3ox2, encoding GA 3‐oxidase, which catalyzes the terminal biosynthetic step, was mainly localized in the cortex and endodermis of embryo axes in germinating seeds. Because another GA biosynthetic gene, AtKO1, coding for ent‐kaurene oxidase, exhibited a similar cell‐specific expression pattern, we predicted that the synthesis of bioactive GAs from ent‐kaurene oxidation occurs in the same cell types during seed germination. We also showed that the cortical cells expand during germination, suggesting a spatial correlation between GA production and response. However, promoter activity of the AtCPS1 gene, responsible for the first committed step in GA biosynthesis, was detected exclusively in the embryo provasculature in germinating seeds. When the AtCPS1 cDNA was expressed only in the cortex and endodermis of non‐germinating ga1–3 seeds (deficient in AtCPS1) using the AtGA3ox2 promoter, germination was not as resistant to a GA biosynthesis inhibitor as expression in the provasculature. These results suggest that the biosynthesis of GAs during seed germination takes place in two separate locations with the early step occurring in the provasculature and the later steps in the cortex and endodermis. This implies that intercellular transport of an intermediate of the GA biosynthetic pathway is required to produce bioactive GAs.
Gene targeting in Arabidopsis
Authors: Hanin Moez , Volrath Sandra , Bogucki Augustyn , Briker Markus , Ward Eric , Paszkowski Jerzy 
Published: March 2003

SummaryPrecise modification by gene targeting (GT) provides an important tool for studies of gene function in vivo. Although routine with many organisms, only isolated examples of GT events have been reported for flowering plants. These were at low frequencies precluding reliable estimation of targeting efficiency and evaluation of GT mechanisms. Here we present an unambiguous and straightforward system for detection of GT events in Arabidopsis using an endogenous nuclear gene encoding protoporphyrinogen oxidase (PPO), involved in chlorophyll and heme syntheses. Inhibition of PPO by the herbicide Butafenacil results in rapid plant death. However, the combination of two particular mutations renders PPO highly resistant to Butafenacil. We exploited this feature for selection of GT events by introducing the mutations into the PPO gene by homologous recombination. We have estimated the basal GT frequency to be 2.4 × 10−3. Approximately one‐third of events were true GT (TGT) leading to the anticipated modification of the chromosomal PPO copy. The remaining events could be classified as ectopic GT (EGT) arising by modification of vector DNA by the chromosomal template and its random integration into the Arabidopsis genome. Thus the TGT frequency in our experimental setup is 0.72 × 10−3. In view of the high efficiency of Arabidopsis transformation, GT experiments of a reasonable size followed by a PCR screen for GT events should also allow for modification of non‐selectable targets. Moreover, the system presented here should contribute significantly to future improvement of GT technology in plants.
APETALA1 and SEPALLATA3 interact to promote flower development
Authors: Pelaz Soraya , Gustafson‐Brown Cindy , Kohalmi Susanne E. , Crosby William L. , Yanofsky Martin F. 
Published: March 2003

SummaryIn Arabidopsis, the closely related APETALA1 (AP1) and CAULIFLOWER (CAL) MADS‐box genes share overlapping roles in promoting flower meristem identity. Later in flower development, the AP1 gene is required for normal development of sepals and petals. Studies of MADS‐domain proteins in diverse species have shown that they often function as heterodimers or in larger ternary complexes, suggesting that additional proteins may interact with AP1 and CAL during flower development. To identify proteins that may interact with AP1 and CAL, we used the yeast two‐hybrid assay. Among the five MADS‐box genes identified in this screen, the SEPALLATA3 (SEP3) gene was chosen for further study. Mutations in the SEP3 gene, as well as SEP3 antisense plants that have a reduction in SEP3 RNA, display phenotypes that closely resemble intermediate alleles of AP1. Furthermore, the early flowering phenotype of plants constitutively expressing AP1 is significantly enhanced by constitutive SEP3 expression. Taken together, these studies suggest that SEP3 interacts with AP1 to promote normal flower development.
TUMOROUS SHOOT DEVELOPMENT (TSD) genes are required for co‐ordinated plant shoot development
Authors: Frank Markus , Guivarc'h Anne , Krupková Eva , Lorenz‐Meyer Irina , Chriqui Dominique , Schmülling Thomas 
Published: March 2003

SummaryThis report describes the identification of novel plant genes that are required to ensure co‐ordinated post‐embryonic development. After germination the tumorous shoot development mutants of Arabidopsis thaliana develop disorganized tumorous tissue instead of organized leaves and stems. This results in green callus‐like structures, which are capable of unlimited growth in vitro on hormone‐free medium. The tsd mutants are recessive and belong to three complementation groups (tsd1, tsd2, tsd3). The genes were mapped to the bottom of chromosomes 5 and 1, and the top of chromosome 3, respectively. Histological analyses showed that the tsd mutants have different developmental defects. The shoot apical meristem of tsd1 formed only rudimentary leaves and was characterized by a degenerating L1 cell layer. tsd2 mutants had reduced cell adhesion and altered cell division planes in the L2 and L3 cell layers. The tumorous tissue of tsd3 mutants originated from the base of the leaf. Cytokinin levels that are inhibitory to the growth of wild‐type seedlings bring about an enhanced growth response in all the tsd mutants. The steady state transcript levels of the histidine kinase CKI1 gene and the KNAT1 and STM homeobox genes were increased in tsd mutants, while mRNA levels of cell cycle genes were not altered. We hypothesize that the TSD gene products negatively regulate cytokinin‐dependent meristematic activity during vegetative development of Arabidopsis.