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M P Running

Publications and source records attributed to M P Running.

12 recordsLinked to original sources
PubMed2001

The role of floral meristems in patterning.

The flower is one of the most complex and varied structures found in plants. Over the past decade, we have begun to understand how floral patterning is established in a handful of model species. Recent studies have identified the presence of several potential pathways for organ patterning. Many genes that are involved in these pathways have been cloned, providing opportunities for further fruitful investigations into the genetic components of flower development.

Magnoliopsida↗
PubMed1999

Signaling of cell fate decisions by CLAVATA3 in Arabidopsis shoot meristems.

In higher plants, organogenesis occurs continuously from self-renewing apical meristems. Arabidopsis thaliana plants with loss-of-function mutations in the CLAVATA (CLV1, 2, and 3) genes have enlarged meristems and generate extra floral organs. Genetic analysis indicates that CLV1, which encodes a receptor kinase, acts with CLV3 to control the balance between meristem cell proliferation and differentiation. CLV3 encodes a small, predicted extracellular protein. CLV3 acts nonautonomously in meristems and is expressed at the meristem surface overlying the CLV1 domain. These proteins may act as a ligand-receptor pair in a signal transduction pathway, coordinating growth between adjacent meristematic regions.

Amino Acid Sequence↗
PubMed1999

The PERIANTHIA gene encodes a bZIP protein involved in the determination of floral organ number in Arabidopsis thaliana.

Mutations in the PERIANTHIA (PAN) gene of Arabidopsis thaliana specifically transform flowers from tetramerous to largely pentamerous, which is a characteristic of flowers of ancestral plants. We have cloned the PAN gene and here we show that it encodes a member of the basic region/leucine zipper class of transcription factors. Immunohistochemical analysis shows that the encoded protein is present in the apical meristem, the floral meristem, each whorl of organ primordia, and in ovule primordia during wild-type flower development. PAN expression occurs independently of genes affecting floral meristem identity, floral meristem size, or floral organ number. The near absence of a phenotype in transgenic plants overexpressing PAN and the contrast between the broad expression of PAN and the specificity of its mutant phenotype suggest that its activity may be regulated post-translationally or by the presence of partner proteins. Based on these results and on data reported previously, we propose models for the role of PAN in the evolution of flower pattern in the mustard family.

Amino Acid Sequence↗
PubMed1999

Disruption of an RNA helicase/RNAse III gene in Arabidopsis causes unregulated cell division in floral meristems.

Arabidopsis thaliana floral meristems are determinate structures that produce a defined number of organs, after which cell division ceases. A new recessive mutant, carpel factory (caf), converts the floral meristems to an indeterminate state. They produce extra whorls of stamens, and an indefinite number of carpels. Thus, CAF appears to suppress cell division in floral meristems. The function of CAF is partially redundant with the function of the CLAVATA (CLV) and SUPERMAN (SUP) genes, as caf clv and caf sup double mutants show dramatically enhanced floral meristem over-proliferation. caf mutant plants also show other defects, including absence of axillary inflorescence meristems, and abnormally shaped leaves and floral organs. The CAF gene was cloned and found to encode a putative protein of 1909 amino acids containing an N-terminal DExH/DEAD-box type RNA helicase domain attached to a C-terminal RNaseIII-like domain. A very similar protein of unknown function is encoded by a fungal and an animal genome. Helicase proteins are involved in a number of processes, including specific mRNA localization and mRNA splicing. RNase III proteins are involved in the processing of rRNA and some mRNA molecules. Thus CAF may act through some type of RNA processing event(s). CAF gives rise to two major transcripts of 2.5 and 6.2 kb. In situ hybridization experiments show that CAF RNA is expressed throughout all shoot tissues.

Amino Acid Sequence↗
PubMed1998

The WIGGUM gene is required for proper regulation of floral meristem size in Arabidopsis.

The study of cell division control within developing tissues is central to understanding the processes of pattern formation. The floral meristem of angiosperms gives rise to floral organs in a particular number and pattern. Despite its critical role, little is known about how cell division is controlled in the floral meristem, and few genes involved have been identified. We describe the phenotypic effects of mutations in WIGGUM, a gene required for control of cell proliferation in the floral and apical meristem of Arabidopsis thaliana. wiggum flowers contain more organs, especially sepals and petals, than found in wild-type flowers. This organ number phenotype correlates with specific size changes in the early floral meristem, preceding organ initiation. Genetic studies suggest that WIGGUM acts on a similar process but in a separate pathway than the CLAVATA1 and CLAVATA3 genes in meristem size regulation, and reveal interactions with other genes affecting meristem structure and identity. Analysis of double mutant phenotypes also reveals a role for WIGGUM in apical meristem function. We propose that WIGGUM plays a role in restricting cell division relative to cellular differentiation in specific regions of the apical and floral meristems.

Arabidopsis↗
PubMed1998

Multiple modes of cell division control in Arabidopsis flower development.

Control of the pattern of cell divisions is central to plant development. Several different types of control exist: examples include control of overall cell number in floral meristems, control of relative cell numbers in floral whorls, and control of the relative spacing of the cell divisions that establish floral organs. Mutations that change each of these levels of control are described: mutations in the SUPERMAN gene affect relative amounts of cell division in adjacent floral whorls; mutations in the CLAVATA genes affect overall meristematic cell number; and mutations in PERIANTHIA affect the spacing of floral organs.

Arabidopsis↗
PubMed1997

Making asymmetric flowers.

The question of how positional information is assigned in floral meristems is beginning to be answered, aided recently by the cloning of a gene responsible for conferring dorsal fate in Antirrhinum majus flowers.

Arabidopsis↗
PubMed1997

TSO1 functions in cell division during Arabidopsis flower development.

We describe an Arabidopsis mutant, tso1, which develops callus-like tissues in place of floral organs. The tso1 floral meristem lacks properly organized three cell layers, and the nuclei of these cells are irregular in size and shape. Further analyses reveal partially formed cell walls and increased DNA ploidy in tso1 floral meristem cells, indicating defects in mitosis and cytokinesis. Our finding that TSO1 is required for organ formation in floral tissues but not in other tissues indicates that TSO1 may encode a floral-specific cell division component, or that TSO1 function is redundant in nonfloral tissues.

Arabidopsis↗
PubMed1996

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

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.

Arabidopsis↗
PubMed1995

Genetic separation of third and fourth whorl functions of AGAMOUS.

AGAMOUS (AG) is an Arabidopsis MADS box gene required for normal development of the third and fourth whorls of the flower. In previously described ag mutants, the third whorl stamens are replaced by petals, and the fourth whorl is replaced by another (mutant) flower. We describe two new ag alleles, ag-4 and AG-Met205, retaining partial AG activity. Both produce flowers with stamens in the third whorl and indeterminate floral meristems; however, ag-4 flowers contain sepals in the fourth whorl, and AG-Met205 produces carpels. The ag-4 mutation results in partial loss of the C terminus of the K domain, a putative coiled coil, and AG-Met205 contains a site-directed mutation that causes a single amino acid change in this same region of the K box. Two models that might explain how these changes in AG result in the separation of different AG activities are discussed.

AGAMOUS Protein, Arabidopsis↗
PubMed1993

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.

Arabidopsis↗