Regulation of accumulation of mRNAs encoding a 20-kDa oil-body protein in microspore-derived embryos of Brassica napus

Abstract

A 990-bp DNA fragment (OB990) encoding part of a 20-kDa Brassica napus oleosin was used to investigate the expression of this gene in microspore-derived embryos. Southern blot analysis of total genomic B. napus DNA indicated that the oleosins comprise a multigene family in B. napus. Northern analysis indicated that oleosin mRNAs are seed-specific and accumulate in zygotic and microspore-derived embryos. Microspore-derived embryos were used to study the hormonal and osmotic regulation of this oleosin gene family. Oleosin mRNAs can be found as early as heart stage. The accumulation of these mRNAs increased dramatically after the application of 10 μM abscisic acid or high osmoticum (12.5% sorbitol). Time course experiments to study the induction of oleosin expression by 10 μM abscisic acid and 12.5% sorbitol demonstrated that the abscisic acid and sorbitol effects occur concurrently. This is distinct from the accumulation of napin storage protein mRNAs after the same treatments. When 10 μM jasmonic acid was applied, the oleosin mRNA accumulation increases significantly. The possibility that jasmonic acid and abscisic acid may function as intermediaries of the imposed osmotic stress is discussed. Key words: Brassica napus, gene regulation, microspore-derived embryos, osmoticum, abscisic acid, jasmonic acid.