THE ABSCISIC ACID-INSENSITIVE3, FUSCA3, AND LEAFY COTYLEDON1 LOCI ACTIN CONCERT TO CONTROL MULTIPLE ASPECTS OF ARABIDOPSIS SEED DEVELOPMENT

Previous studies have shown that recessive mutations at the Arabidopsi s ABSCISIC ACID-INSENSITIVE3 (ABI3), FUSCA3 (FUS3), and LEAN COP/LEDON 1 (LEC1) loci lead to various abnormalities during mid-embryogenesis a nd late embryogenesis. In this study, we investigated whether these lo ci act in independent regulatory pathways or interact in controlling c ertain facets of seed development. Several developmental responses wer e quantified in abi3, fus3, and lec1 single mutants as well as in doub le mutants combining either the weak abi3-1 or the severe abi3-4 mutat ions with either fus3 or lec1 mutations. Our data indicate that ABI3 i nteracts genetically with both FUS3 and LEC1 in controlling each of th e elementary processes analyzed, namely, accumulation of chlorophyll a nd anthocyanins, sensitivity to abscisic acid, and expression of indiv idual members of the 12S storage protein gene family. In addition, bot h FUS3 and LEC1 regulate positively the abundance of the ABI3 protein in the seed. These results suggest that in contrast to previous models , the ABI3, FUS3, and LEC1 genes act synergistically to control multip le elementary processes during seed development.