Characterization of the CHD proteins in Arabidopsis
Abstract
PICKLE (PKL) encodes a CHD3 protein that is involved in the repression of embryonic identity after germination in Arabidopsis. CHD proteins are thought to remodel chromatin as a means of gene regulation. pkl mutants are named after the accumulation of green tissue that can develop at the primary root of the seedling. The "pickle root" has the ability to form somatic embryos and continues to express embryonic genes, suggesting embryonic identity is not properly repressed after germination. The penetrance of the pickle root phenotype is strongly dependent on levels of the plant hormone Gibberellin (GA). Another relationship between PKL and GA is that pkl plants express shoot phenotypes that are similar to a GA deficient plant (dark green leaves, delayed bolting, reduced branching of trichomes, reduced apical dominance, and reduced stature), suggesting PKL is involved in GA signaling. In this study, I further examine the expression and localization of PKL protein and transcript. I demonstrate that PKL protein is nuclear localized and that expression and localization are unaffected by the addition or subtraction of GA. I also determine that pkl germinating seedlings do not properly repress the embryonic genes (LEC1 and LEC2 ). In addition, I demonstrate that lowering endogenous levels of GA during germination increases the level of transcript in these embryonic genes, suggesting that both PKL and GA play a role in repressing embryonic identity in germinating seedlings. By performing a domain deletion analysis of PKL, I identified potential dominant negative forms of PKL. Further characterization of these dominant negative forms of PKL reveal that endogenous levels of PKL protein are reduced but not transcript, suggesting that these forms of PKL function at the level of protein. Finally I characterized the other CHD genes in Arabidopsis and identified a CHD3 variant that is similar to PKL but lacks a PHD zinc finger domain. Further characterization PKR2 revealed that the protein and transcript are only detected in embryonic tissue and that PKL and PKR2 function redundantly to repress embryonic identity in Arabidopsis.
Degree
Ph.D.
Advisors
Ogas, Purdue University.
Subject Area
Molecular biology
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