The overexpression of a mutant Brassica 3-hydroxy-3-methylglutaryl-CoA synthase A in transgenic model plant, tobacco, promotes growth and seed yield

Abstract

3-Hydroxy-3-methylglutaryl-CoA synthase (HMGS) is an enzyme in the mevalonate pathway of isoprenoid biosynthesis. We have previously cloned cDNAs encoding HMGS from Brassica juncea (Indian mustard), designated as BjHMGS1 to BjHMGS4. We have shown that recombinant mutant enzyme, BjHMGS1 (S359A), displayed a 10-fold higher enzyme activity than the the the wild type. When wild-type BjHMGS1 and mutant BjHMGS1 (S359A) were introduced in Arabidopsis, belonging to the same family Brassicaceae, several genes in sterol biosynthesis were up-regulated and phytosterols accumulated. The ectopic expression of BjHMGS1 (S359A) in tobacco, a more phylogenetically distant model plant of the family Solanaceae, further caused increase in plant growth, pod size and seed yield. These changes suggest that S359A has potential applications in agriculture. The S359A line is expected to yield interesting information when tested using genomic technologies.