Genetic and biochemical characterization of <italic>BAM1</italic> and <italic>BAM2</italic>, regulators of multiple aspects of development in <italic>Arabidopsis thaliana</italic>.
DeYoung, Brody John
2004
Abstract
The ability of plants to form organs throughout their lifespan is due to the activity of stem cells located at the meristem. Genetic studies have revealed the role of a number of genes that regulate this critical process including the <italic>CLAVATA</italic> (<italic>CLV</italic>) loci. Mutation in <italic>CLV1, CLV2</italic>, or <italic>CLV3</italic> result in an accumulation of stem cells in the shoot and floral meristems and genetic analysis has shown that these genes act in a common pathway. <italic>CLV1</italic> encodes a leucine-rich repeat receptor kinase. While most <italic>clv1</italic> alleles are dominant-negative, <italic>clv1</italic> null alleles are very weak in phenotype, suggesting the presence of parallel receptors. I have identified two such receptors, BAM1 and BAM2. I show that the weak phenotype of <italic> clv1</italic> null alleles is dependent on <italic>BAM</italic> activity. Furthermore, <italic>BAM</italic> activity in the meristem depends on <italic> CLV</italic>2. Surprisingly, <italic>bam1</italic> and <italic>bam2</italic> mutants suppress the phenotypes of <italic>clv3</italic>. CLV3 is a small, secreted protein that is predicted to be the ligand for CLV1. I propose a model in which BAM1 and BAM2 act to sequester a CLV3-like ligand in the meristem. <italic> bam1 bam2</italic> plants exhibit dramatic defects in the development of every aerial organ. Hence, BAM1 and BAM2 play a role in the regulation of a large number of diverse developmental events. This is in contrast to the majority of plant receptor kinases characterized to date. In addition, clv1 mutants enhance many of the Bam<super>-</super> mutant phenotypes outside of the meristem, indicating that, contrary to current understanding, CLV1 function is not meristem specific. Overexpression and misexpression studies show that CLV1 is able to rescue all of the <italic>bam1 bam2</italic> mutant phenotypes. Likewise, BAM1 and BAM2 can partially replace CLV1 function in the meristem, however they are not fully equivalent to CLV1. I have also characterized some basic biochemical properties of CLV1, BAM1, and BAM2. I show that BAM1 and BAM2 may exist in disulfide-linked forms, and that CLV1, BAM1, and BAM2 are glycoproteins. In addition, I show that BAM1 is rapidly degraded under certain protein extraction conditions and that BAM1 is primarily associated with membranes. Finally, I show that BAM1 is eluted from a size exclusion chromatography column in fractions that correspond to molecular masses much larger than that predicted for BAM1.Subjects
Arabidopsis Aspects Bam1 Bam2 Biochemical Characterization Clavata Development Genetic Meristem Multiple Regulators Stem Cells Thaliana
Types
Thesis
Metadata
Show full item recordCollections
Remediation of Harmful Language
The University of Michigan Library aims to describe library materials in a way that respects the people and communities who create, use, and are represented in our collections. Report harmful or offensive language in catalog records, finding aids, or elsewhere in our collections anonymously through our metadata feedback form. More information at Remediation of Harmful Language.
Accessibility
If you are unable to use this file in its current format, please select the Contact Us link and we can modify it to make it more accessible to you.