Authors: Darleen A DeMason Rekha Chawla
Publish Date: 2003/08/27
Volume: 218, Issue: 3, Pages: 435-448
Abstract
The goal of this study was to explore the impact of the plant growth regulator auxin on the development of compound leaves in pea Wildtype WT plantlets as well as those of two leaf mutants acacia tl and tendrilled acacia unitac of pea Pisum sativum L were grown on media containing the auxintransport inhibitors 235triiodobenzoic acid TIBA N1naphthylphthalamic acid NPA or the auxin antagonist pchlorophenoxyisobutyric acid PCIB The resulting plantlets were carefully analyzed morphologically by scanning electron microscopy and for Uni gene expression using quantitative reverse transcription–polymerase chain reaction Auxin transport was measured in WT leaf parts using 14Cindole3acetic acid Relative Uni gene expression was determined in shoot tips of a range of leafform mutants Morphological abnormalities were observed for all genotypes examined The terminal tendrils on WT plants were converted to leaflets stubs or were aborted The number of pinna pairs produced on leaves was reduced with the distal forms being eliminated before the proximal ones Some leaves were converted to simple including triand bilobed forms These treatments phenocopy the unitac and unifoliata uni mutants of pea In the most extreme situations leaf blades were completely lost leaving only a pair of stipules or scale leaves Polar auxin transport was basipetal for all leaf parts Uni gene expression in shoot tips was significantly reduced in 60 μM NPA and TIBA Uni mRNA was more abundant in tl af and af tl and reduced in the uni mutants compared to WT These results indicate that an auxin gradient plays fundamental roles in controlling morphogenesis in the compound leaves of pea and specifically it i is the driving force for leaf growth and pinna determination ii is necessary for pinna initiation and iii controls subsequent pinna developmentThe authors thank Janet Giles for her technical assistance with the tissue culture experiments and for performing the Uni expression analyses and Dr William Thomson for comments on the manuscript The SEM was done in the Analytical Microscopy Facility at the University of California Riverside The pea genotypes used in this study were obtained from the Marx Collection which currently resides at the USDA–ARS Pacific West Area This work was supported by a grant from USDA/CSREES 20013530410958 to the first author
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