Analysis of cell signaling during floral abscission in arabidopsis

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The shedding of plant organs is known as abscission. Floral abscission in Arabidopsis is regulated by two related receptor¬-like protein kinases (RLKs), HAESA and HAESA¬-like 2 (HAE/HSL2). Double mutants of HAE/HSL2 are completely defective in abscission and retain sepals, petals, and stamen indefinitely. We have utilized genetic suppressor screens of hae hsl2 mutant to identify additional regulatory mechanisms of floral abscission. We have uncovered a series of gain-of-function alleles of the receptor-like protein kinase gene SERK1, as well as loss of function alleles of the gene MAP-KINASE-PHOSPHATASE-1/MKP1. We further show that mutation of two components of the endoplasmic reticulum-associated protein degradation system can suppress a weak hae hsl2 mutant, suggesting that the weak hae hsl2 mutant receptor proteins undergo ER-associated protein degradation. We further perform a number of experiments to examine the impact of phosphorylation on the activity of HAE. These results provide a number of important mechanistic details to our understanding of floral abscission, and suggest many lines of inquiry for future research.