Poster: Lipids & related molecules

Abs # 312: Rice Oxylipin Pathway: An Indication of the Complex Adaptative Responses to Environmental Stimuli

Presenter:	Chehab, E. Wassim , ewchehab@ucdavis.edu
Authors	Chehab, E. Wassim  (A)   Banu, Gopalan  (A) (B)  Raman, Girija  (A)   Dehesh, (Katie) Katayoon  (A)
Affiliations:	(A): University of California, Davis (B): Pacific Northwest National Laboratory

Oxylipins comprise a large family of metabolites which play an important role in a set of biological functions. The production of these metabolites is catalyzed by several enzymes including AOS (allene oxide synthase) and HPL (hydroperoxide lyase). These two enzymes compete for the same substrates and are responsible for the production of antimicrobial compounds such as jasmonic acid and aromatic compounds such as aldehydes. We have chosen rice as a model system to study the AOS and HPL pathways as this crop offers many advantages including the availability of its genome sequence, a food staple as well its adaptability to a wide range of environmental conditions including oxygen tensions. We have conducted thorough database searches and confirmed that the rice genome contains one HPL and four AOS genes, the highest number reported so far. Phylogenetic analysis of all the available AOS/HPL sequences revealed that three of the AOSs and the HPL from rice are closely related to their monocot orthologs, while the fourth AOS is related to its dicot orthologs. To further dissect the roles of AOS/HPL enzymes in rice, we have employed genetic, bioinformatic, molecular and biochemical techniques. Our data show that these genes differ in their spatial and temporal expression patterns and that their encoded products differ in subcellular localizations, thereby reflecting their functional differences. This data, together with genetic complementation, and molecular modeling validated by in vitro enzyme assays, provide a detailed understanding of the physiological role of these enzymes in response to complex stress signals.