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

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

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

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 clv1mutations. 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

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

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

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

Using Confocal Microscopy in the Study of Plant Structure and Development

The widespread application of confocal laser scanning microscopy has revolutionized biological imaging. We have developed a protocol for using confocal microscopy to examine the development of wild type and mutant Arabidopsis thaliana, overcoming the technical difficulties associated with examining whole-mounted plant tissue. This allowed us to rapidly determine the underlying cellular defects that lead to the morphological changes visible in several mutants, and has led to a greater understanding of the mechanisms involved in the control of floral organ number

The Study of PPAL and its Role in the Development of Physcomitrella patens

Protein Prenylation is the addition of lipids to select proteins that play a key role during the development of plants. There are three enzymes that play a role in protein prenylation: protein farnesyltransferase (PFT), protein geranylgeranyl-transferase-I (PGGT), and Rab geranylgeranyltransferase (Rab-GGT). However, there is a protein called PPAL that has a similar alpha subunit of PFT, PGGT, and RAB-GGT but its biochemical function is unknown. Physconmitrella patens, a type of moss, was chosen to explore the role of PpPPAL in the development process. There are two copies of PPAL found in moss. PPAL1 and PPAL2. To study the role of these genes, a partial knockdown line was created where one or both alpha and beta subunit genes was reduced. An artificial microRNA was created to target the PpPPAL1 and PpPPAL2 genes and was introduced into the moss via a plasmid. Once the microRNA was inserted into the moss, the moss was grown in DMSO/ beta-estradiol medium to start the suppression of gene expression. The results showed that the knockout of PpPPAL 1 and PpPPAL 2 inhibits the growth and propagation of physconmitrella patens. They also resulted in a few gametophore contents. The result indicates that PPAL plays an important role in the developmental process in P.patents. The role of PPAL in protein prenylation of physconmitrella patens give insights into how prenylation works in humans since defects in prenylation can lead to health problemshttps://ir.library.louisville.edu/uars/1069/thumbnail.jp

The Sterilization of Escherichia coli with Black Diamond-Coated Silicon

In order to combat increasing levels of antimicrobial resistance, new antimicrobials are needed to successfully kill microbes. Silicon coated in black diamond is a material that is hypothesized to have antimicrobial properties. To test this hypothesis, Escherichia coli cells were placed on different black diamond-coated silicon surfaces and allowed to rest on each surface for 15 minutes, 30 minutes, and 1 hour. Cells were collected, and growth was assessed by counting colonies on plates or spectrophotometry growth curves. The results of this study indicated that the experimental samples have some antimicrobial or growth inhibition properties, but they may not be to the extent as hypothesized. Errors in the harvesting method were likely present, and the experimental technique is currently being modified to collect the maximum number of cells for growth assessment

The Effects of PPAL-1 in Arabidopsis Gamete Development

Prenylation is a type of post-translational modification in which a 15- or 20-carbon lipid is added to the carboxyl (C) terminus of the protein. Arabidopsis thaliana contains the PROTEIN PRENYLTRANSFERASE ALPHA SUBUNIT-LIKE (PPAL) gene, which encodes a protein with homology to the α-subunits of the three known prenylation enzymes, PFT, PGGT, and Rab-GGT. We previously identified two mutations in PPAL, one of which is ppal-1, which contains a T-DNA insertion in the fourth intron. We have previously observed that self-fertilizing heterozygous ppal-1 plants produce progeny in which homozygous ppal-1 is underrepresented. This project attempts to ascertain possible affects of ppal-1 in gametophyte growth and development that might cause this underrepresented homozygous ppal-1 population. Crosses were performed between homozygous ppal-1 and wild-type (WT) plants. Both F0 and F1 generations were genotyped. The results indicated that there was WT contamination of the ppal-1 F0 population. The data also indicated the ppal-1 primers were nonfunctional. Additionally, a pollen germination test was performed for both ppal-1and WT plants. The results indicated that ppal-1 pollen had developmental delays for germination, but upon germination, they could form pollen tubules of equal length to the WT pollen. However, due to the likely WT contamination in the ppal-1 population used, these experiments must be replicated in further studies