Poster: Hormones

Abs # 602: Genetic analysis of IBA-response mutants reveal novel components in peroxisomal processes

Presenter:	Adham, Ana R, radham@rice.edu
Authors	Adham, Ana R (A)   Millius, Arthur  (A)   Bartel, Bonnie  (A)
Affiliations:	(A): Rice University

Auxin is an important plant hormone that influences virtually all aspects of plant growth and development. Despite auxin’s ubiquitous involvement in plant processes, we are only beginning to understand how auxin levels are regulated. There are at least two endogenous forms of auxin, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA), previously thought to only exist as a synthetic auxin. IBA appears to undergo a two-carbon elimination reaction similar to the one used in peroxisomal fatty acid b-oxidation to yield IAA. To understand the roles of IBA in plants, we are using forward and reverse genetics to isolate IBA- response (ibr) mutants that display enhanced root elongation on inhibitory concentrations of IBA and yet maintain a wild-type phenotype on IAA. These mutants may have aberrations in genes involved in IBA conversion or perception. We have categorized these mutants into three classes based on their root and hypocotyl phenotypes under various hormone, sugar, and light conditions: 1) those with defects in peroxisome or fatty acid b-oxidation, which directly or indirectly disrupt IBA conversion to IAA, 2) those that have defects particularly in b-oxidation of IBA, and 3) those without defects in b-oxidation, which may be defective in IBA perception . Interestingly, some ibr mutants with defects in b-oxidation map to regions lacking any genes known to function in peroxisomal processes. These mutants may define novel components that have yet to be identified in other organisms.