Plant & Animal Genomes XI Conference

January 11-15, 2003
Town & Country Convention Center
San Diego, CA

Workshop: Cool Season Legumes
            

GENETIC AND HORMONAL CONTROL OF LEAF DEVELOPMENT IN PEA

Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA

To determine what roles auxin might play in leaf development of pea (Pisum sativum): (1) wildtype plantlets and those of the various leaf mutants were grown on media containing the auxin transport inhibitors TIBA, NPA, or on the auxin analog, PCIB; and (2) expression of various auxin signaling and response genes was determined in shoot tips of the leaf mutants using RT-PCR. When grown on auxin inhibitors, consistent morphological abnormalities were observed for all genotypes and the severity increased with concentration. The terminal tendrils on wildtype plants were converted to leaflets, stubs or were aborted. The number of pinna pairs was reduced, with the distal forms lost before the proximal ones. Some leaves were simple. These results phenocopy the unifoliata mutants. Also, leaf blades were lost leaving only stipules and leaf initiation ceased on some plantlets. Leaves of afila genotypes had reduced pinna branching and some were converted from pinnately to palmately compound. Uni expression was reduced. Differential expression of Pinoid, PIN1, Aux/IAA 4/5, and Aux/IAA6 was found in the leaf mutants. These results indicate that auxin plays similar fundamental roles in leaf development of all the genotypes of pea but their auxin status varies. Specifically, an auxin gradient: (1) drives leaf primordium growth and pinna initiation; (2) controls pinna determination along the leaf axis; and (3) causes branching of compound pinnae.