Glycerol-3-Phosphate Acyltransferase 6 (GPAT6) Is Important for Tapetum Development in Arabidopsis and Plays Multiple Roles in Plant Fertility

Glycerol-3-phosphate acyltransferase (GPAT) mediates the initial synthetic step for the formation of glycerolipids, which act as the major components of biological membranes and the principal stored forms of energy. GPAT6 is a member of the Arabidopsis GPAT family, which is crucial for cutin biosynthesis in sepals and petals. In this work, a functional analysis of GPAT6 in anther development and plant fertility was performed. GPAT6 was highly expressed in the tapetum and microspores during anther development. The knockout mutant, gpat6, caused a massive reduction in seed production. This report shows that the ablation of GPAT6 caused defective tapetum development with reduced endoplasmic reticulum (ER) profiles in the tapetum, which largely led to the abortion of pollen grains and defective pollen wall formation. In addition, pollen germination and pollen tube elongation were affected in the mutant plants. Furthermore, the double mutant analysis showed that GPAT6 and GPAT1 make joint effects on the release of microspores from tetrads and stamen filament elongation. This work shows that GPAT6 plays multiple roles in stamen development and fertility in Arabidopsis.