Lateral Suppressor Research Articles

Inhibition of chrysanthemum axillary buds via transformation with the antisense tomato lateral suppressor gene is season dependent

The lateral suppressor (Ls) genes have a conserved role in axillary meristem initiation in diverse plants. Transgenic chrysanthemum (Dendranthema × grandiflorum) carrying antisense Ls cDNA was generated using Agrobacterium-mediated transformation. Totally 139 shoots were obtained as transformants, and with 5 transgenic plants selected in the preliminary observation, shoot branching was screened on 3 different planting dates. The number of axillary buds in the transgenic plants was changed over season. Axillary buds were visible in all axils in the April planting, but the number of axillary buds was reduced in the June planting in 3 transformants. The biggest reduction in the number of axillary buds was found in Ls80, whose antisense Ls transcript was the highest. The percentage of axillary buds in Ls80 decreased from 100% to 26% when the planting date was delayed from April 26 to June 15, but increased again to 55.9% on the August 12 planting. Anatomical assay suggest that the loss of axillary buds was as a result of defects in initiating axillary meristem. Transgenic plants carrying the Ls antisense gene displayed several floral morphological differences in comparison with nontransgenic control ‘Jinba’. Typical abnormal features in the plants included lobbed petals and a stamen-like structure around the style. We conclude that the Ls gene has a conserved role in axillary meristem initiation in chrysanthemum and might interact with other temperature-dependent genes.

Expression profiling of tomato pre-abscission pedicels provides insights into abscission zone properties including competence to respond to abscission signals

BackgroundDetachment of plant organs occurs in abscission zones (AZs). During plant growth, the AZ forms, but does not develop further until the cells perceive abscission-promoting signals and initiate detachment. Upon signal perception, abscission initiates immediately; if there is no signal, abscission is not induced and the organ remains attached to the plant. However, little attention has been paid to the genes that maintain competence to respond to the abscission signal in the pre-abscission AZ. Recently, we found that the tomato (Solanum lycopersicum) transcription factors BLIND (Bl), GOBLET (GOB), Lateral suppressor (Ls) and a tomato WUSCHEL homologue (LeWUS) are expressed specifically in pre-abscission tissue, the anthesis pedicel AZs. To advance our understanding of abscission, here we profiled genome-wide gene expression in tomato flower pedicels at the pre-abscission stage.ResultsWe examined the transcriptomes of three tomato flower pedicel regions, the AZ and flanking proximal- (Prox) and distal- (Dis) regions, and identified 89 genes that were preferentially expressed in the AZ compared to both Prox and Dis. These genes included several transcription factors that regulate apical or axillary shoot meristem activity. Also, genes associated with auxin activity were regulated in a Prox-Dis region-specific manner, suggesting that a gradient of auxin exists in the pedicel. A MADS-box gene affecting floral transition was preferentially expressed in the Prox region and other MADS-box genes for floral organ identification were preferentially expressed in Dis, implying that the morphologically similar Prox and Dis regions have distinct identities. We also analyzed the expression of known regulators; in anthesis pedicels, Bl, GOB, Ls and LeWUS were expressed in the vascular cells of the AZ region. However, after an abscission signal, Bl was up-regulated, but GOB, Ls and LeWUS were down-regulated, suggesting that Bl may be a positive regulator of abscission, but the others may be negative regulators.ConclusionsThis study reveals region-specific gene expression in tomato flower pedicels at anthesis and identifies factors that may determine the physiological properties of the pre-abscission pedicel. The region-specific transcriptional regulators and genes for auxin activity identified here may prevent flower abscission in the absence of signal or establish competence to respond to the abscission signal.

Transcriptome Analysis of Tomato Flower Pedicel Tissues Reveals Abscission Zone-Specific Modulation of Key Meristem Activity Genes

Tomato flower abscises at the anatomically distinct abscission zone that separates the pedicel into basal and apical portions. During abscission, cell separation occurs only at the abscission zone indicating distinctive molecular regulation in its cells. We conducted a transcriptome analysis of tomato pedicel tissues during ethylene promoted abscission. We found that the abscission zone was the most active site with the largest set of differentially expressed genes when compared with basal and apical portions. Gene Ontology analyses revealed enriched transcription regulation and hydrolase activities in the abscission zone. We also demonstrate coordinated responses of hormone and cell wall related genes. Besides, a number of ESTs representing homologs of key Arabidopsis shoot apical meristem activity genes were found to be preferentially expressed in the abscission zone, including WUSCHEL (WUS), KNAT6, LATERAL ORGAN BOUNDARIES DOMAIN PROTEIN 1(LBD1), and BELL-like homeodomain protein 1 (BLH1), as well as tomato axillary meristem genes BLIND (Bl) and LATERAL SUPPRESSOR (Ls). More interestingly, the homologs of WUS and the potential functional partner OVATE FAMILIY PROTEIN (OFP) were subsequently down regulated during abscission while Bl and AGL12 were continuously and specifically induced in the abscission zone. The expression patterns of meristem activity genes corroborate the idea that cells of the abscission zone confer meristem-like nature and coincide with the course of abscission and post-abscission cell differentiation. Our data therefore propose a possible regulatory scheme in tomato involving meristem genes that may be required not only for the abscission zone development, but also for abscission.

Rice APC/CTE controls tillering by mediating the degradation of MONOCULM 1

Rice MONOCULM 1 (MOC1) and its orthologues LS/LAS (lateral suppressor in tomato and Arabidopsis) are key promoting factors of shoot branching and tillering in higher plants. However, the molecular mechanisms regulating MOC1/LS/LAS have remained elusive. Here we show that the rice tiller enhancer (te) mutant displays a drastically increased tiller number. We demonstrate that TE encodes a rice homologue of Cdh1, and that TE acts as an activator of the anaphase promoting complex/cyclosome (APC/C) complex. We show that TE coexpresses with MOC1 in the axil of leaves, where the APC/CTE complex mediates the degradation of MOC1 by the ubiquitin–26S proteasome pathway, and consequently downregulates the expression of the meristem identity gene Oryza sativa homeobox 1, thus repressing axillary meristem initiation and formation. We conclude that besides having a conserved role in regulating cell cycle, APC/CTE has a unique function in regulating the plant-specific postembryonic shoot branching and tillering, which are major determinants of plant architecture and grain yield.

Cloning of aZoysia ZjLsLand its overexpression to induce axillary meristem initiation and tiller formation inArabidopsisand bentgrass

Zoysia grass and creeping bentgrass are important turf grasses used in parks, gardens and playing fields. Development of grasses with increased tiller formation will enhance their commercial cultivation. To investigate the regulatory mechanism of tiller formation, we cloned the Zoysia japonica Lateral suppressor-like (ZjLsL) gene. The Lateral suppressor (Ls) gene encodes a transcriptional regulator belonging to the plant-specific GRAS protein family of putative transcription factors, and regulates axillary meristem initiation. A full-length DNA of the ZjLsL gene was isolated by 5'/3' DNA walking. Phylogenetic analysis showed that ZjLsL is closely related to Ls genes. Southern blot analysis revealed that zoysia grass has two copies of the ZjLsL gene. ZjLsL expression was detected in all organs of zoysia grass but was most highly expressed in culms. Overexpression of ZjLsL in creeping bentgrass and Arabidopsis plants promoted axillary bud formation. These results suggest that ZjLsL plays an important role in axillary meristem initiation and tiller formation.

MACROCALYX and JOINTLESS Interact in the Transcriptional Regulation of Tomato Fruit Abscission Zone Development

Abscission in plants is a crucial process used to shed organs such as leaves, flowers, and fruits when they are senescent, damaged, or mature. Abscission occurs at predetermined positions called abscission zones (AZs). Although the regulation of fruit abscission is essential for agriculture, the developmental mechanisms remain unclear. Here, we describe a novel transcription factor regulating the development of tomato (Solanum lycopersicum) pedicel AZs. We found that the development of tomato pedicel AZs requires the gene MACROCALYX (MC), which was previously identified as a sepal size regulator and encodes a MADS-box transcription factor. MC has significant sequence similarity to Arabidopsis (Arabidopsis thaliana) FRUITFULL, which is involved in the regulation of fruit dehiscent zone development. The MC protein interacted physically with another MADS-box protein, JOINTLESS, which is known as a regulator of fruit abscission; the resulting heterodimer acquired a specific DNA-binding activity. Transcriptome analyses of pedicels at the preabscission stage revealed that the expression of the genes involved in phytohormone-related functions, cell wall modifications, fatty acid metabolism, and transcription factors is regulated by MC and JOINTLESS. The regulated genes include homologs of Arabidopsis WUSCHEL, REGULATOR OF AXILLARY MERISTEMS, CUP-SHAPED COTYLEDON, and LATERAL SUPPRESSOR. These Arabidopsis genes encode well-characterized transcription factors regulating meristem maintenance, axillary meristem development, and boundary formation in plant tissues. The tomato homologs were specifically expressed in AZs but not in other pedicel tissues, suggesting that these transcription factors may play key roles in pedicel AZ development.

Shoot Branching and Leaf Dissection in Tomato Are Regulated by Homologous Gene Modules

Aerial plant architecture is predominantly determined by shoot branching and leaf morphology, which are governed by apparently unrelated developmental processes, axillary meristem formation, and leaf dissection. Here, we show that in tomato (Solanum lycopersicum), these processes share essential functions in boundary establishment. Potato leaf (C), a key regulator of leaf dissection, was identified to be the closest paralog of the shoot branching regulator Blind (Bl). Comparative genomics revealed that these two R2R3 MYB genes are orthologs of the Arabidopsis thaliana branching regulator REGULATOR OF AXILLARY MERISTEMS1 (RAX1). Expression studies and complementation analyses indicate that these genes have undergone sub- or neofunctionalization due to promoter differentiation. C acts in a pathway independent of other identified leaf dissection regulators. Furthermore, the known leaf complexity regulator Goblet (Gob) is crucial for axillary meristem initiation and acts in parallel to C and Bl. Finally, RNA in situ hybridization revealed that the branching regulator Lateral suppressor (Ls) is also expressed in leaves. All four boundary genes, C, Bl, Gob, and Ls, may act by suppressing growth, as indicated by gain-of-function plants. Thus, leaf architecture and shoot architecture rely on a conserved mechanism of boundary formation preceding the initiation of leaflets and axillary meristems.

Specific expression of LATERAL SUPPRESSOR is controlled by an evolutionarily conserved 3′ enhancer

Aerial plant architecture is largely based on the activity of axillary meristems (AMs), initiated in the axils of leaves. The Arabidopsis gene LATERAL SUPPRESSOR (LAS), which is expressed in well-defined domains at the adaxial boundary of leaf primordia, is a key regulator of AM formation. The precise definition of organ boundaries is an essential step for the formation of new organs in general and for meristem initiation; however, mechanisms leading to these specific patterns are not well understood. To increase understanding of how the highly specific transcript accumulation in organ boundary regions is established, we investigated the LAS promoter. Analysis of deletion constructs revealed that an essential enhancer necessary for complementation is situated about 3.2 kb downstream of the LAS open reading frame. This enhancer is sufficient to confer promoter specificity as upstream sequences in LAS could be replaced by non-specific promoters, such as the 35S minimal promoter. Further promoter swapping experiments using the PISTILLATA or the full 35S promoter demonstrated that the LAS 3' enhancer also has suppressor functions, largely overwriting the activity of different 5' promoters. Phylogenetic analyses suggest that LAS function and regulation are evolutionarily highly conserved. Homologous elements in downstream regulatory sequences were found in all LAS orthologs, including grasses. Transcomplementation experiments demonstrated the functional conservation of non-coding sequences between Solanum lycopersicum (tomato) and Arabidopsis. In summary, our results show that a highly conserved enhancer/suppressor element is the main regulatory module conferring the boundary-specific expression of LAS.

The Cucumber Lateral Suppressor Gene (CLS) Is Functionally Associated with Axillary Meristem Initiation

To elucidate the genetic and molecular mechanisms of plant architecture, a Cucumber Lateral Suppressor gene (CLS) for the lateral branching development in cucumber branching line S06 was cloned and characterized. Full-length cDNA of CLS (EU503217) was isolated by performing rapid amplification of cDNA ends polymerase chain reaction. Phylogenetic analysis showed that the gene CLS is closely related to Lateral Suppressor that encodes transcriptional regulator proteins belonging to GRAS family of known transcription factor. Southern blot analysis revealed that CLS gene has one copy in cucumber genome. The expression patterns revealed that transcripts were detected in all organs, but not in internodes. In addition, the transcript level in male flowers is higher than the female flowers and fruit. Introduction of the Pro35s:CLS overexpression vector into Arabidopsis las plants led to a full complementation of the mutant phenotypes. Moreover, RNA in situ hybridization showed that the pattern of CLS transcript was accumulated in the leaf axils in different developmental stage, which was similar to LAS in Arabidopsis. These results together indicate that CLS may play an important role in cucumber axillary meristem initiation and thus the lateral branch formation.

Genetic analysis of reproductive development in tomato

Besides being an important commercial crop, tomato (Solanum lycopersicum L.) constitutes a model species for the study of plant developmental processes. Current research tends to combine classic disciplines such as physiology and genetics with modern approaches coming from molecular biology and genomics with a view to elucidating the biological mechanisms underlying plant architecture, floral transition and development of flowers and fruits. Comparative and functional analyses of tomato regulatory genes such as LATERAL SUPPRESSOR (LS), SELF PRUNING (SP), SINGLE FLOWER TRUSS (SFT) and FALSIFLORA (FA) have revealed mechanisms involved in shoot development and flowering time which are conserved among Arabidopsis, tomato and other plant species. Furthermore, several regulatory genes encoding transcription factors have been characterized as responsible for singular features of vegetative and reproductive development of tomato. Thus, the sympodial growth habit seems to require a specific control of the developmental fate followed by shoot meristems. In this process, novel genetic and molecular interactions involving SP, SFT and FA genes would be essential. Also this latter, but mainly ANANTHA (AN) and COMPOUND INFLORESCENCE (S) have recently been found to regulate the inflorescence architecture of the tomato. Concerning fruit development, genetic and molecular analyses of new genes such as fw2.2, FASCIATED, OVATE and SUN have proved their contribution to the domestication process and most importantly, their function as key regulators of fruit size and shape variation. Tomato ripening is also being elucidated thanks to the characterization of regulatory genes such as RIPENING INHIBITOR (RIN), NON-RIPENING (NOR), TDR4 and COLORLESS NON-RIPENING (CNR), which have been found to control early stages of fruit development and maturation. At the same time, much research is dedicated to isolating the targets of the ripening regulators, as well as the key genes promoting the parthenocarpic development of tomato fruits. Hopefully, the ongoing sequencing project and the progress made by integrating several research fields will help to unravel the genetic and molecular pathways controlling tomato development.

Signals Derived fromYABBYGene Activities in Organ Primordia Regulate Growth and Partitioning ofArabidopsisShoot Apical Meristems

Shoot apical meristems (SAMs) are self-sustaining groups of cells responsible for the ordered initiation of all aerial plant tissues, including stems and lateral organs. The precise coordination of these processes argues for crosstalk between the different SAM domains. The products of YABBY (YAB) genes are limited to the organ primordium domains, which are situated at the periphery of all SAMs and which are separated by a margin of three to seven cells from the central meristem zone marked by WUSCHEL and CLAVATA3 expression. Mutations in the two related YAB1 genes, FILAMENTOUS FLOWER and YABBY3 (YAB3), cause an array of defects, including aberrant phyllotaxis. We show that peripheral YAB1 activity nonautonomously and sequentially affects the phyllotaxis and growth of subsequent primordia and coordinates the expression of SAM central zone markers. These effects support a role for YAB1 genes in short-range signaling. However, no evidence was found that YAB1 gene products are themselves mobile. A screen for suppression of a floral YAB1 overexpression phenotype revealed that the YAB1-born signals are mediated in part by the activity of LATERAL SUPPRESSOR. This GRAS protein is expressed at the boundary of organ primordia and the SAM central zone, distinct from the YAB1 expression domain. Together, these results suggest that YAB1 activity stimulates signals from the organs to the meristem via a secondary message or signal cascade, a process essential for organized growth of the SAM.

Selection of non-branching lines induced by introducing Ls-like cDNA into Chrysanthemum ( Dendranthema × grandiflorum (Ramat.) Kitamura) “Shuho-no-chikara”

A partial Ls-like cDNA (525bp) was isolated from Chrysanthemum “95B1-45” line, which exhibited a non-branching characteristic. The fragments showed homology with lateral suppressor ( Ls) partial cDNA from tomato that stimulated the initiation of axillary meristems. After the fragments was constructed with sense and antisense versions, these constructs were employed in Agrobacterium-mediated transformation of Chrysanthemum ( Dendranthema × grandiflorum (Ramat.) Kitamura) “Shuho-no-chikara”. The leaf segments (5 mm × 5 mm) from in vitro shoots were inoculated with Agrobacterium cultures for 10 min and co-cultured with Agrobacterium tumefaciens for three days at 25 °C. Transgenic plants were obtained only in Agrobacterium C58C1 containing pCAMBIA2301 constructed with Ls-like partial cDNA in antisense version. Forty shoots (1 was in positive control and 39 in Ls-antisense version) in Agrobacterium C58C1 were confirmed as putative transformants in PCR analysis with nptII primer. In the Southern analysis, results showed that 35 of the 39 shoots integrated npt II gene were confirmed to contain Ls-like partial cDNA in antisense version. Therefore, the 35 transformants were multiplied and planted in green house for integrated Ls-like partial cDNA expression. One (2.9%) among the 36 transformed lines showed lateral bud inhibition of more than 40%, with another one (2.9%) in lateral bud inhibition of 20–30%, and the remaining ones in less than 20%. However, in the second investigation (in a lateral branch in October 29), nine lines belonged to the range of 20–30% lateral bud inhibition and the remaining ones were in the range of less than 20%. The expression of non-branching characteristics showed significant difference even in the same line according to season.

Arabidopsis CUP-SHAPED COTYLEDON3Regulates Postembryonic Shoot Meristem and Organ Boundary Formation

Overall shoot architecture in higher plants is highly dependent on the activity of embryonic and axillary shoot meristems, which are produced from the basal adaxial boundaries of cotyledons and leaves, respectively. In Arabidopsis thaliana, redundant functions of the CUP-SHAPED COTYLEDON genes CUC1, CUC2, and CUC3 regulate embryonic shoot meristem formation and cotyledon boundary specification. Their functional importance and relationship in postembryonic development, however, is poorly understood. Here, we performed extensive analyses of the embryonic and postembryonic functions of the three CUC genes using multiple combinations of newly isolated mutant alleles. We found significant roles of CUC2 and CUC3, but not CUC1, in axillary meristem formation and boundary specification of various postembryonic shoot organs, such as leaves, stems, and pedicels. In embryogenesis, all three genes make significant contributions, although CUC3 appears to possess, at least partially, a distinct function from that of CUC1 and CUC2. The function of CUC3 and CUC2 overlaps that of LATERAL SUPPRESSOR, which was previously shown to be required for axillary meristem formation. Our results reveal that redundant but partially distinct functions of CUC1, CUC2, and CUC3 are responsible for shoot organ boundary and meristem formation throughout the life cycle in Arabidopsis.

BlindHomologousR2R3 MybGenes Control the Pattern of Lateral Meristem Initiation inArabidopsis

In seed plants, shoot branching is initiated during postembryonic development by the formation of secondary meristems. These new meristems, which are established between the stem and leaf primordia, develop into vegetative branches or flowers. Thus, the number of axillary meristems has a major impact on plant architecture and reproductive success. This study describes the genetic control of axillary meristem formation in Arabidopsis thaliana by a group of three R2R3 Myb genes, which are homologous to the tomato (Solanum lycopersicum) Blind gene and were designated REGULATORS OF AXILLARY MERISTEMS (RAX). rax mutants show new phenotypes that are characterized by defects in lateral bud formation in overlapping zones along the shoot axis. RAX genes are partially redundant in function and allow a fine-tuning of secondary axis formation. As revealed by monitoring of SHOOT MERISTEMLESS transcript accumulation, the RAX genes control a very early step of axillary meristem initiation. The RAX1 and RAX3 expression domains specifically mark a cell group in the center of the leaf axil from which the axillary meristem develops. Double mutant combinations of lateral suppressor and rax1-3 as well as expression studies suggest that at least two pathways control the initiation of axillary meristems in Arabidopsis.

Cloning, characterization and expression of a Lateral suppressor- like gene from chrysanthemum ( Dendranthema grandiflorum Kitamura)

Conventionally, the lateral shoots of chrysanthemum are removed manually, which is time consuming and uneconomical. The development of branchless chrysanthemum will economize its commercial cultivation. To investigate the regulatory mechanism of branchlessness, we undertook cloning of Dendranthema grandiflorum Kitamura Lateral suppressor-like ( DgLsL) gene for development of lateral shoot in chrysanthemum. A full-length cDNA of DgLsL gene was isolated by screening cDNA library and performing Rapid Amplification of cDNA Ends (RACE) PCR. Phylogenetic analysis showed that the DgLsL gene is closely related to Lateral suppressor that encodes transcriptional regulator proteins belonging to GRAS family of known transcription factor. Southern blot analysis revealed that DgLsL gene in chrysanthemum genome has one copy. DgLsL expression was apparently up-regulated by ethephon treatment. The expression patterns revealed that DgLsL transcripts were detected in all organs, but showed their highest level in stems.

JOINTLESS suppresses sympodial identity in inflorescence meristems of tomato

Unlike monopodial plants, in which flowering terminates growth of a shoot, plants exhibiting sympodial shoot architecture maintain the potential for indeterminate growth even after converting to floral development. This vegetative indeterminacy is conferred by a special type of axillary meristem, the sympodial meristem, which exhibits precocious but determinate growth. The reiterative formation of sympodial meristems as the plant grows results in a shoot composed of a series of modules, each consisting of a limited number of vegetative nodes and terminated by a flower or inflorescence. To determine how sympodial meristems differ from other shoot meristems, we examined interactions between mutations that affect various shoot meristem types in tomato (Lycopersicon esculentum Mill.). Analysis of double mutant combinations of jointless, lateral suppressor, self-pruning, blind, and anantha showed that sympodial meristems share regulatory features with inflorescence meristems. Genetic studies on the jointless mutation implicated this gene in suppressing sympodial meristem fate in the inflorescence. As this mutation has a second phenotype, the elimination of the pedicel abscission zone, we examined the expression pattern of JOINTLESS to test whether pedicel development is involved in directing shoot architecture. We found that this MADS box gene is expressed in a variety of shoot meristems, including inflorescence, floral, sympodial, and axillary meristems, as well as in early staged floral organs, in sporogenous tissues of anthers, and in ovules. Lack of expression in developing pedicels indicates abscission zone development does not rely on JOINTLESS transcription in the differentiating cells. We conclude that the primary role of JOINTLESS is to suppress sympodial meristem identity in inflorescence meristems.

Comparative analysis of axillary and floral meristem development

Axillary and floral meristems are shoot meristems that initiate postembryonically. In Arabidopsis, axillary meristems give rise to branches during vegetative development while floral meristems give rise to flowers during reproductive development. This review compares the development of these meristems from their initiation at the shoot apical meristem up to the establishment of their specific developmental fates. Axillary and floral meristems originate from lateral primordia that form at flanks of the shoot apical meristem. Initial development of vegetative and reproductive primordia are similar, resulting in the formation of a morphologically defined primordium partitioned into adaxial and abaxial domains. The adaxial primordial domain is competent to form a meristem, while the abaxial domain correlates with the formation of a leaf. This review proposes that all primordia partition into domains competent to form the meristem and the leaf. According to this model, a vegetative primordium develops as leaf-bias while a reproductive primordium develops as meristem-bias.Key words: SHOOTMERISTEMLESS, LATERAL SUPPRESSOR, AINTEGUMENTA, adaxial primordial domain, abaxial primordial domain, shoot morphogenesis.

Identification and characterization of two new members of the GRAS gene family in rice responsive to N-acetylchitooligosaccharide elicitor

We identified two new members of the GRAS gene family from rice, CIGR1 and CIGR2, which are rapidly induced upon N-acetylchitooligosaccharide elicitor perception. The predicated proteins encoded by CIGR1 and CIGR2 possess significant sequence similarity with previously identified members of the GRAS family, such as Arabidopsis SCARECROW, GAI, RGA, tomato Lateral suppressor, and rice SLR1, all of which have VHIID regions, likely to play a role in cellular signaling. Fusions of CIGR1 and CIGR2 with Green Fluorescent Protein were detected exclusively in the nuclei of onion epidermal cells. The expression of CIGR1 and CIGR2 was dependent on the structure of N-acetylchitooligosaccharides, which parallels the structural specificity for chitin binding to the plasma membrane-localized chitin-binding protein, and independent of de novo protein synthesis. Co-cultivation of rice cells with rice blast fungus strongly induced the expression of CIGR1 and CIGR2, whereas inoculation of suspension cells with phytopathogenic bacteria did not. We hypothesize that CIGR1 and CIGR2 act as transcriptional regulators in the early events of the elicitor-induced defense response in rice.

Comparative Sequence Analysis Reveals Extensive Microcolinearity in the Lateral Suppressor Regions of the Tomato, Arabidopsis, and Capsella Genomes

Comparative Sequence Analysis Reveals Extensive Microcolinearity in the Lateral Suppressor Regions of the Tomato, Arabidopsis, and Capsella Genomes

The Lateral suppressor (Ls) gene of tomato encodes a new member of the VHIID protein family.

The ability of the shoot apical meristem to multiply and distribute its meristematic potential through the formation of axillary meristems is essential for the diversity of forms and growth habits of higher plants. In the lateral suppressor mutant of tomato the initiation of axillary meristems is prevented, thus offering the unique opportunity to study the molecular mechanisms underlying this important function of the shoot apical meristem. We report here the isolation of the Lateral suppressor gene by positional cloning and show that the mutant phenotype is caused by a complete loss of function of a new member of the VHIID family of plant regulatory proteins.