Rahman, Tawhidur .
Brassinosteroid, abscisic acid and calcium: determining the connection.
Brassinosteroids (BRs) are a group of plant polyhydroxysteroids that have been established as essential regulators of plant growth and development. In addition to their pivotal role in plant growth and development, BRs are also known to protect plants from various abiotic and biotic stresses. We have demonstrated that exogenous treatment of Arabidopsis thaliana with 24-epibrassinolide (EBR), a BR, confers tolerance to a range of abiotic stresses like high and low temperatures, high salt and drought. Previous studies as well as those conducted in our lab have implicated interaction between BR and abscisic acid (ABA), another important phytohormone involved in abiotic stress tolerance in plants. We have found ABA biosynthesis and ABA-responsive genes to be up-regulated by EBR treatment. This treatment also promotes the basic thermotolerance in both ABA-deficient (aba1-1) and ABA-insensitive (abi1-1) mutants. Though the accumulation of heat shock proteins (hsps) was higher in both EBR-treated aba1-1 and abi1-1 seedlings as compared to untreated seedlings, a more dramatic effect of EBR on hsp levels was observed in the aba1-1 mutant. Since Ca++/calmodulin appears to play a role in BR biosynthesis, ABA signaling and in sensing and transducing environmental stimuli, we are studying the functions of two genes encoding calmodulin-like calcium-binding proteins that were identified in our microarray screen to be up-regulated by EBR. The T-DNA insertion mutant of one of these genes was found to be hypersensitive to ABA in germination assays and to show developmental defects in response to EBR. Further studies are aimed at testing the roles of these genes in relation to BR, ABA and stress responses.
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1 - University of Western Ontario, Biology, 1151 Richmond Streeet N. Department of Biology, Unversity of Western, Ontario, London, Ontario, N6A 5B7, Canada
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM