Biomedical subjects
Steven E Clark
Publications and source records attributed to Steven E Clark.
POLTERGEIST encodes a protein phosphatase 2C that regulates CLAVATA pathways controlling stem cell identity at Arabidopsis shoot and flower meristems.
BACKGROUND: Receptor kinases are a large gene family in plants and have more than 600 members in Arabidopsis. Receptor kinases in plants regulate a broad range of developmental processes, including steroid hormone perception, organ elongation, self-incompatibility, and abscission. Intracellular signaling components for receptor kinases in plants are largely unknown. The CLAVATA 1 (CLV1) receptor kinase in Arabidopsis regulates stem cell identity and differentiation through its repression of WUSCHEL (WUS) expression. Mutations at the POLTERGEIST (POL) gene were previously described as phenotypic suppressors of mutations within the CLV1 gene. Genetic evidence placed POL as a downstream regulator of CLAVATA1 signaling. RESULTS: We provide evidence that POL functions in both the CLV1-WUS pathway and a novel WUS-independent CLV1 pathway regulating stem cell identity. We demonstrate that POL encodes a protein phosphatase 2C (PP2C) with a predicted nuclear localization sequence, indicating that it has a role in signal transduction downstream of the CLV1 receptor. The N terminus of POL has a possible regulatory function, and the C terminus has PP2C-like phosphatase catalytic activity. Although the POL catalytic domain is conserved in other PP2Cs, the POL protein represents a unique subclass of plant PP2Cs. POL is broadly expressed throughout the plant. CONCLUSIONS: POL represents a novel component of the CLV1 receptor kinase signaling pathway. The ubiquitous expression of POL and pol phenotypes outside the meristem suggest that POL may be a common regulator of many signaling pathways.
Using mutant alleles to determine the structure and function of leucine-rich repeat receptor-like kinases.
The leucine-rich-repeat class of receptor-like kinase (RLK)-encoding genes represents the largest class of putative receptor-encoding genes in the Arabidopsis genome. The biological functions of several of these genes have been determined through genetic analysis. With dozens of mutant alleles described for various RLKs in Arabidopsis and other plants, comparisons of the mutations found in different receptors, as well as of structural features that are conserved between receptors, can provide insights into the common and/or divergent regulation and functions of these receptors.
CLAVATA1 dominant-negative alleles reveal functional overlap between multiple receptor kinases that regulate meristem and organ development.
The CLAVATA1 (CLV1) receptor kinase controls stem cell number and differentiation at the Arabidopsis shoot and flower meristems. Other components of the CLV1 signaling pathway include the secreted putative ligand CLV3 and the receptor-like protein CLV2. We report evidence indicating that all intermediate and strong clv1 alleles are dominant negative and likely interfere with the activity of unknown receptor kinase(s) that have functional overlap with CLV1. clv1 dominant-negative alleles show major differences from dominant-negative alleles characterized to date in animal receptor kinase signaling systems, including the lack of a dominant-negative effect of kinase domain truncation and the ability of missense mutations in the extracellular domain to act in a dominant-negative manner. We analyzed chimeric receptor kinases by fusing CLV1 and BRASSINOSTEROID INSENSITIVE1 (BRI1) coding sequences and expressing these in clv1 null backgrounds. Constructs containing the CLV1 extracellular domain and the BRI1 kinase domain were strongly dominant negative in the regulation of meristem development. Furthermore, we show that CLV1 expressed within the pedicel can partially replace the function of the ERECTA receptor kinase. We propose the presence of multiple receptors that regulate meristem development in a functionally related manner whose interactions are driven by the extracellular domains and whose activation requires the kinase domain.