7-day old phenotype of fln mutants. Seeds segregating for fln alleles grown under a 16 h photoperiod at 18o C. Homozygous individuals are circled.
(Gilkerson et al., 2012)
(Gilkerson et al., 2012)
General structure for a RING-HC domain showing spacing
between metal-binding residues
(Stone et al, 2005)
(Stone et al, 2005)
Auxin accelerates the degradation of IAA1:LUC
in Arabidopsis seedlings
(Zenser et al, 2001)
in Arabidopsis seedlings
(Zenser et al, 2001)
We are studying the function of the family of phosphofructokinase-B (pfkB) type proteins in plants. The Callis lab has begun characterization of two of these members, fructokinase like protein 1 and 2 (FLN1, -2), in Arabidopsis and found both to be important during chloroplast development. These proteins were found by other groups to associate with the plastid encoded RNA polymerase (PEP) complex, which transcribes a subset of genes in the plastid mainly having to do with photosynthetic and translational machinery. One group has published data showing an association with FLN proteins and thioredoxin-Z (TRXZ), which is also a member of the PEP complex. Plants lacking either FLN or TRXZ have similar chlorotic phenotypes due to poor development of chloroplasts in these plants. Poor development of the chloroplasts is likely due, in part, to a lack of certain PEP encoded transcripts but the molecular mechanism of FLN protein involvement in the observed phenotype remains unknown. We are using tools from both molecular biology and biochemistry to study the molecular mechanisms that lead to the chlorotic phenotype seen in the absence of FLN proteins. A more general aim of this research project is to begin characterization of the other ~20 uncharacterized members of the pfkB family in A. thaliana. All of these proteins are part of the pfkB family and, as such, have been annotated as carbohydrate kinases. However, their carbohydrate specificity and the possible pathways they may operate in are still unknown. We are using a number of techniques to provide insights into the function of these proteins such as: fluorescent tagging and microscopy to determine their localization, comparative genomics and other bioinformatics tools to generate testable hypotheses about their possible functions, and finally both molecular and biochemical methods to test those hypotheses.
We are examining the activity of another family of proteins containing RING and variant RING domains. These domains have been implicated in the E3 ubiquitin ligase activity of many proteins. We seek to identify putative proteins containing these domains, verify their ligase activity using in vitro ubiquitination assays, identify interacting partners, and characterize their function in vivo by studying the phenotypes of plants with mutations in RING-domain-containing proteins.
Auxin signal transduction requires the ubiquitin/proteasome pathway. We are interested in studying the degradation of the AUX/IAA family of transcriptional repressors as well as other components of auxin signaling pathways. We hope to characterize the regions required for recognition of the proteolytic targets, and to learn more about the ways in which auxin affects the rate of proteolysis of specific substrates.
The Callis lab is in the Department of Molecular and Cellular Biology, within the College of Biological Sciences at UC Davis |
||