Abstract
In developing Arabidopsis seeds, assembly of triacylglycelols (TAGs) from fatty acids synthesized in chloroplasts takes place in the endoplasmic reticulumn, and expression of genes involved in TAG assembly such as DGAT1 coding for diacylglycerol acyltransferase follows the expression of genes involved in fatty acid synthesis. A DREB subfamily transcription factor A2, with expression patterns during seed maturation similar to that of DGAT1, trans-activated transient expression of DGAT1:LUC reporter gene in protoplasts. The DGAT1 promoter contained a DRE sequence, and mutation in the DRE site of DGAT1:LUC abolished the trans-activation by A2. Recombinant A2 showed binding to the DRE sequence in vitro. A T-DNA insertion line of A2 showed reduced levels of DGAT1 mRNA in developing fruits compared to the wild type, but seed oil content was not significantly affected. A T-DNA insertion line of a gene for a close homolog of A2 also showed reduced DGAT1 mRNA in fruits, suggesting that they may share overlapping roles. Since the 35S:DGAT1 plants showed reduced DGAT1 mRNA probably due to co-suppression, we are preparing plants expressing A2 under the control of a seed-specific promoter.
