OLEOSIN GENE-EXPRESSION IN ARABIDOPSIS-THALIANA TAPETUM COINCIDES WITH ACCUMULATION OF LIPIDS IN PLASTIDS AND CYTOPLASMIC BODIES

Oleosins are alkaline proteins found on the surface of oil bodies in p lants. They serve a structural role in stabilizing the triacylglycerol s of the oil bodies together with the phos pholipid layer. We studied the spatial and temporal expression pat;ern of three putative oleosin genes atgrp-6, atgrp-7, and atgrp-8, in anthers of Arabidopsis thalian a using RNA transcript in situ hybridization. For all three genes, tra nscripts were found within the tapetal cells during the process of sen escence. To identify a putative function for corresponding proteins, t he tapetum was characterized ultrastructurally by electron microscopy and analyzed cytochemically for the presence of unsaturated lipids and basic proteins. TWO lipid storage organelles were identified: elaiopl astids and lipid protein bodies. The accumulation of lipids in these t wo organelles strictly coincides with oleosin gene expression in the t apetum of A. rhaliana. No typical oil body was observed during tapetum development. A putative function of oleosins in tapetal cells is disc ussed.