Lower Levels of Expression of FATA2 Gene Promote Longer Siliques with Modified Seed Oil Content in Arabidopsis thaliana

Fatty acyl thioesterases control the termination of intraplastidial fatty acid synthesis by hydrolyzing fatty acyl-ACP complexes. The fatty acyl thioesterase A (FATA) gene family in Arabidopsis comprises two members, i.e., FATA1 and FATA2. Previous studies have shown that FATAs display high specificity for unsaturated fatty acids. However, the expression pattern and individual roles of these two FATA genes remains unknown. In this study, we initially studied the expression patterns of FATA1 and FATA2 in various organs of Arabidopsis and we found that FATA1 was expressed at low level in all organs examined and FATA2 was detected in all organs examined, with especially high accumulation in siliques. The transient expression of a FATA2-eGFP fusion in Arabidopsis green leaf protoplasts showed that FATA2 was localized in chloroplasts. A T-DNA insertion mutant line of FATA2 (named fata2) was obtained and used for phenotypic observation. Semiquantitative RT-PCR assay showed that the expression level of FATA2 decreased significantly in fata2 compared with that in wild type. Furthermore, fata2 mutants produced longer siliques with more seeds, whereas seed size was slightly smaller than that of wild type. Compositional analysis of seed oil revealed that, except for a subtly decreased C24:0 and unchanged C22:0 level, all other fatty acids were increased by between 10 and 60 % in fata2 dry seeds compared with those in wild-type. Taken together, our results indicate that FATA2 plays important roles in lipid metabolism in seeds and in silique development in Arabidopsis thaliana.