CLAVATA1, a regulator of meristem and flower development in Arabidopsis

We have investigated the effects on plant development of mutations in the Arabidopsis thaliana CLAVATA1 gene. In clavata1 plants, vegetative, inflorescence and floral meristems are all enlarged relative to wild type. The apical meristem can fasciate in the more severe mutant alleles, and this fasciation can occur prior to the transition to flowering. Flowers of clavata1 plants can have increased numbers of organs in all four whorls, and can also have additional whorls not present in wild-type flowers. Double mutant combinations of clavata1 with agamous, apetala2, apetala3 and pistillata indicate that CLAVATA1 controls the underlying floral meristem structure upon which these homeotic genes act. Double mutant combinations of clavata1 with apetala1 and leafy indicate CLAVATA1 plays a role in establishing and maintaining floral meristem identity, in addition to its role in controlling meristem size. In support of this, RNA expression patterns of AGAMOUS and APETALA1 are altered in clavata1 flowers.

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CLAVATA3 is a specific regulator of shoot and floral meristem development affecting the same processes as CLAVATA1

Development ◽

10.1242/dev.121.7.2057 ◽

1995 ◽

Vol 121 (7) ◽

pp. 2057-2067 ◽

Cited By ~ 26

Author(s):

S. E. Clark ◽

M. P. Running ◽

E. M. Meyerowitz

Keyword(s):

Arabidopsis Thaliana ◽

Flower Development ◽

Mature Embryo ◽

Floral Meristem ◽

Wild Type ◽

Apical Meristems ◽

Meristem Development ◽

Embryo Stage ◽

Double Heterozygosity ◽

Floral Meristems

We have previously described the phenotype of Arabidopsis thaliana plants with mutations at the CLAVATA1 (CLV1) locus (Clark, S. E., Running, M. P. and Meyerowitz, E. M. (1993) Development 119, 397–418). Our investigations demonstrated that clv1 plants develop enlarged vegetative and inflorescence apical meristems, and enlarged and indeterminate floral meristems. Here, we present an analysis of mutations at a separate locus, CLAVATA3 (CLV3), that disrupt meristem development in a manner similar to clv1 mutations. clv3 plants develop enlarged apical meristems as early as the mature embryo stage. clv3 floral meristems are also enlarged compared with wild type, and maintain a proliferating meristem throughout flower development. clv3 root meristems are unaffected, indicating that CLV3 is a specific regulator of shoot and floral meristem development. We demonstrate that the strong clv3-2 mutant is largely epistatic to clv1 mutants, and that the semi- dominance of clv1 alleles is enhanced by double heterozygosity with clv3 alleles, suggesting that these genes work in the same pathway to control meristem development. We propose that CLV1 and CLV3 are required to promote the differentiation of cells at the shoot and floral meristem.

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OsMADS32 Regulates Rice Floral Patterning through Interactions with Multiple Floral Homeotic Genes

Journal of Experimental Botany ◽

10.1093/jxb/eraa588 ◽

2020 ◽

Author(s):

Yun Hu ◽

Li Wang ◽

Ru Jia ◽

Wanqi Liang ◽

Xuelian Zhang ◽

...

Keyword(s):

Flower Development ◽

Floral Organ ◽

Floral Meristem ◽

Homeotic Genes ◽

Dependent Manner ◽

Floral Meristem Identity ◽

Floral Homeotic Genes ◽

Organ Identity ◽

Meristem Identity ◽

Floral Homeotic

Abstract Floral patterning is regulated by intricate networks of floral identity genes. The peculiar MADS32 subfamily genes, absent in eudicots but prevalent in monocots, regulate floral organ identity. However, how the MADS32 family genes interact with other floral homeotic genes during flower development is mostly unknown. We show here that the rice homeotic transcription factor OsMADS32 regulates floral patterning by interacting synergistically with E class protein OsMADS6 in a dosage-dependent manner. Furthermore, our results indicate important roles of OsMADS32 in defining stamen, pistil and ovule development through physical and genetic interactions with OsMADS1, OsMADS58 and OsMADS13, and in specifying floral meristem identity with OsMADS6, OsMADS3 and OsMADS58 respectively. Our findings suggest that OsMADS32 is an important factor for floral meristem identity maintenance and that it integrates the action of other MADS-box homeotic proteins to sustain floral organ specification and development in rice. Given that OsMADS32 is an orphan gene and absent in eudicots, our data substantially expand our understanding of flower development in plants.

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The indeterminate floral apex1 gene regulates meristem determinacy and identity in the maize inflorescence

Development ◽

10.1242/dev.129.11.2629 ◽

2002 ◽

Vol 129 (11) ◽

pp. 2629-2638 ◽

Cited By ~ 1

Author(s):

Debbie Laudencia-Chingcuanco ◽

Sarah Hake

Keyword(s):

Double Mutant ◽

Floral Meristem ◽

Marker Genes ◽

Integrated Process ◽

Inflorescence Meristem ◽

Mutant Analysis ◽

Lateral Organs ◽

Meristem Identity ◽

Mutant Phenotypes ◽

Floral Meristems

Meristems may be determinate or indeterminate. In maize, the indeterminate inflorescence meristem produces three types of determinate meristems: spikelet pair, spikelet and floral meristems. These meristems are defined by their position and their products. We have discovered a gene in maize, indeterminate floral apex1 (ifa1) that regulates meristem determinacy. The defect found in ifa1 mutants is specific to meristems and does not affect lateral organs. In ifa1 mutants, the determinate meristems become less determinate. The spikelet pair meristem initiates more than a pair of spikelets and the spikelet meristem initiates more than the normal two flowers. The floral meristem initiates all organs correctly, but the ovule primordium, the terminal product of the floral meristem, enlarges and proliferates, expressing both meristem and ovule marker genes. A role for ifa1 in meristem identity in addition to meristem determinacy was revealed by double mutant analysis. In zea agamous1 (zag1) ifa1 double mutants, the female floral meristem converts to a branch meristem whereas the male floral meristem converts to a spikelet meristem. In indeterminate spikelet1 (ids1) ifa1 double mutants, female spikelet meristems convert to branch meristems and male spikelet meristems convert to spikelet pair meristems. The double mutant phenotypes suggest that the specification of meristems in the maize inflorescence involves distinct steps in an integrated process.

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The WUSCHEL gene is required for shoot and floral meristem integrity in Arabidopsis

Development ◽

10.1242/dev.122.1.87 ◽

1996 ◽

Vol 122 (1) ◽

pp. 87-96 ◽

Cited By ~ 24

Author(s):

T. Laux ◽

K.F. Mayer ◽

J. Berger ◽

G. Jurgens

Keyword(s):

Developmental Stages ◽

Shoot Meristem ◽

Wild Type ◽

Recessive Mutations ◽

Organ Identity ◽

Flat Structures ◽

Meristem Identity ◽

Wus Gene ◽

Floral Meristems ◽

Shoot Meristems

Self perpetuation of the shoot meristem is essential for the repetitive initiation of shoot structures during plant development. In Arabidopsis shoot meristem maintenance is disrupted by recessive mutations in the WUSCHEL (WUS) gene. The defect is evident at all developmental stages and is restricted to shoot and floral meristems, whereas the root meristem is not affected. wus mutants fail to properly organize a shoot meristem in the embryo. Postembryonically, defective shoot meristems are initiated repetitively but terminate prematurely in aberrant flat structures. In contrast to wild-type shoot meristems, primordia initiation occurs ectopically across mutant apices, including the center, and often new shoot meristems instead of organs are initiated. The cells of wus shoot apices are larger and more vacuolated than wild-type shoot meristem cells. wus floral meristems terminate prematurely in a central stamen. Double mutant studies indicate that the number of organ primordia in the center of wus flowers is limited, irrespective of organ identity and we propose that meristem cells are allocated into floral whorl domains in a sequential manner. WUS activity also appears to be required for the formation of supernumerary organs in the center of agamous, superman or clavata1 flowers, suggesting that the WUS gene acts upstream of the corresponding genes. Our results suggest that the WUS gene is specifically required for central meristem identity of shoot and floral meristems to maintain their structural and functional integrity.

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The ULTRAPETALA gene controls shoot and floral meristem size in Arabidopsis

Development ◽

10.1242/dev.128.8.1323 ◽

2001 ◽

Vol 128 (8) ◽

pp. 1323-1333 ◽

Cited By ~ 4

Author(s):

J.C. Fletcher

Keyword(s):

Signal Transduction Pathway ◽

Floral Meristem ◽

Transduction Pathway ◽

Wild Type ◽

Inflorescence Meristem ◽

Genetic Studies ◽

Meristem Cell ◽

Meristem Size ◽

Cell Accumulation ◽

Floral Meristems

The regulation of proper shoot and floral meristem size during plant development is mediated by a complex interaction of stem cell promoting and restricting factors. The phenotypic effects of mutations in the ULTRAPETALA gene, which is required to control shoot and floral meristem cell accumulation in Arabidopsis thaliana, are described. ultrapetala flowers contain more floral organs and whorls than wild-type plants, phenotypes that correlate with an increase in floral meristem size preceding organ initiation. ultrapetala plants also produce more floral meristems than wild-type plants, correlating with an increase in inflorescence meristem size without visible fasciation. Expression analysis indicates that ULTRAPETALA controls meristem cell accumulation partly by limiting the domain of CLAVATA1 expression. Genetic studies show that ULTRAPETALA acts independently of ERA1, but has overlapping functions with PERIANTHIA and the CLAVATA signal transduction pathway in controlling shoot and floral meristem size and meristem determinacy. Thus ULTRAPETALA defines a novel locus that restricts meristem cell accumulation in Arabidopsis shoot and floral meristems.

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Developmental and Molecular Changes Underlying the Vernalization-Induced Transition to Flowering in Aquilegia coerulea (James)

Genes ◽

10.3390/genes10100734 ◽

2019 ◽

Vol 10 (10) ◽

pp. 734 ◽

Cited By ~ 1

Author(s):

Bharti Sharma ◽

Timothy A. Batz ◽

Rakesh Kaundal ◽

Elena M. Kramer ◽

Uriah R. Sanders ◽

...

Keyword(s):

Flowering Time ◽

Apical Meristem ◽

Genetic Basis ◽

Model Systems ◽

Molecular Changes ◽

Rnaseq Data ◽

And Cluster Analysis ◽

Reproductive Phases ◽

Floral Meristems ◽

Transition To Flowering

Reproductive success in plants is dependent on many factors but the precise timing of flowering is certainly among the most crucial. Perennial plants often have a vernalization or over-wintering requirement in order to successfully flower in the spring. The shoot apical meristem undergoes drastic developmental and molecular changes as it transitions into inflorescence meristem (IM) identity, which then gives rise to floral meristems (FMs). In this study, we have examined the developmental and gene expression changes underlying the transition from the vegetative to reproductive phases in the basal eudicot Aquilegia coerulea, which has evolved a vernalization response independently relative to other established model systems. Results from both our histology and scanning electron studies demonstrate that developmental changes in the meristem occur gradually during the third and fourth weeks of vernalization. Based on RNAseq data and cluster analysis, several known flowering time loci, including AqFT and AqFL1, exhibit dramatic changes in expression during the fourth week. Further consideration of candidate gene homologs as well as unexpected loci of interest creates a framework in which we can begin to explore the genetic basis of the flowering time transition in Aquilegia.

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Mutations in the PERIANTHIA gene of Arabidopsis specifically alter floral organ number and initiation pattern

Development ◽

10.1242/dev.122.4.1261 ◽

1996 ◽

Vol 122 (4) ◽

pp. 1261-1269 ◽

Cited By ~ 10

Author(s):

M.P. Running ◽

E.M. Meyerowitz

Keyword(s):

Floral Organ ◽

Floral Meristem ◽

Wild Type ◽

Organ Identity ◽

The Family ◽

Dividing Cells ◽

Meristem Identity ◽

Plant Families ◽

Open Question ◽

Floral Organ Identity Genes

An open question in developmental biology is how groups of dividing cells can generate specific numbers of segments or organs. We describe the phenotypic effects of mutations in PERIANTHIA, a gene specifically required for floral organ patterning in Arabidopsis thaliana. Most wild-type Arabidopsis flowers have 4 sepals, 4 petals, 6 stamens, and 2 carpels. Flowers of perianthia mutant plants most commonly show a pentamerous pattern of 5 sepals, 5 petals 5 stamens, and 2 carpels. This pattern is characteristic of flowers in a number of plant families, but not in the family Brassicaceae, which includes Arabidopsis. Unlike previously described mutations affecting floral organ number, perianthia does not appear to affect apical or floral meristem sizes, nor is any other aspect of vegetative or floral development severely affected. Floral organs in perianthia arise in a regular, stereotypical pattern similar to that in distantly related species with pentamerous flowers. Genetic analysis shows that PERIANTHIA acts downstream of the floral meristem identity genes and independently of the floral meristem size and floral organ identity genes in establishing floral organ initiation patterns. Thus PERIANTHIA acts in a previously unidentified process required for organ patterning in Arabidopsis flowers.

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The early-flowering mutant efs is involved in the autonomous promotion pathway of Arabidopsis thaliana

Development ◽

10.1242/dev.126.21.4763 ◽

1999 ◽

Vol 126 (21) ◽

pp. 4763-4770 ◽

Cited By ~ 3

Author(s):

W.J. Soppe ◽

L. Bentsink ◽

M. Koornneef

Keyword(s):

Arabidopsis Thaliana ◽

Flowering Time ◽

Double Mutant ◽

Plant Size ◽

Early Flowering ◽

Wild Type ◽

Late Flowering ◽

Long Day ◽

Short Days ◽

Transition To Flowering

The transition to flowering is a crucial moment in a plant's life cycle of which the mechanism has only been partly revealed. In a screen for early flowering, after mutagenesis of the late-flowering fwa mutant of Arabidopsis thaliana, the early flowering in short days (efs) mutant was identified. Under long-day light conditions, the recessive monogenic efs mutant flowers at the same time as wild type but, under short-day conditions, the mutant flowers much earlier. In addition to its early-flowering phenotype, efs has several pleiotropic effects such as a reduction in plant size, fertility and apical dominance. Double mutant analysis with several late-flowering mutants from the autonomous promotion (fca and fve) and the photoperiod promotion (co, fwa and gi) pathways of flowering showed that efs reduces the flowering time of all these mutants. However, efs is completely epistatic to fca and fve but additive to co, fwa and gi, indicating that EFS is an inhibitor of flowering specifically involved in the autonomous promotion pathway. A vernalisation treatment does not further reduce the flowering time of the efs mutant, suggesting that vernalisation promotes flowering through EFS. By comparing the length of the juvenile and adult phases of vegetative growth for wild-type, efs and the double mutant plants, it is apparent that efs mainly reduces the length of the adult phase.

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Genetic control of branching pattern and floral identity during Petunia inflorescence development

Development ◽

10.1242/dev.125.4.733 ◽

1998 ◽

Vol 125 (4) ◽

pp. 733-742 ◽

Cited By ~ 5

Author(s):

E. Souer ◽

A. van der Krol ◽

D. Kloos ◽

C. Spelt ◽

M. Bliek ◽

...

Keyword(s):

In Situ Hybridisation ◽

Floral Meristem ◽

Branching Pattern ◽

Inflorescence Meristem ◽

Inflorescence Architecture ◽

Phenotypic Analysis ◽

Inflorescence Development ◽

Meristem Identity ◽

Floral Meristems

A main determinant of inflorescence architecture is the site where floral meristems are initiated. We show that in wild-type Petunia bifurcation of the inflorescence meristem yields two meristems of approximately equal size. One terminates into a floral meristem and the other maintains its inflorescence identity. By random transposon mutagenesis we have generated two mutants in which the architecture of the inflorescence is altered. In the extra petals- (exp) mutant the inflorescence terminates with the formation of a single terminal flower. Phenotypic analysis showed that exp is required for the bifurcation of inflorescence meristems. In contrast, the aberrant leaf and flower- (alf) mutant is affected in the specification of floral meristem identity while the branching pattern of the inflorescence remains unaltered. A weak alf allele was identified that, after bifurcation of the inflorescence meristem, yields a ‘floral’ meristem with partial inflorescence characteristics. By analysing independent transposon dTph1 insertion alleles we show that the alf locus encodes the Petunia FLORICAULA/LEAFY homolog. In situ hybridisation shows that alf is expressed in the floral meristem and also in the vegetative meristem. Differences and similarities between these Petunia mutants and mutations affecting inflorescence architecture in other species will be discussed.

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