The 3-Hydroxy-3-methylglutaryl-coenzyme A synthase (HMGS) of the mevalonate
pathway produces phytosterols, which can lower blood cholesterol levels. In
a previous study, the overexpression of the BjHMGS1 synthase from mustard
(Brassica juncea) increased sterol content in Arabidopsis.
Using the same method, the team of Pan Liao from the University of Hong Kong
aims to increase the production of antioxidants in tomato (Solanum
lycopersicum). The team overexpressed the BjHMGS1 genes from both wildtype
and the mustard mutant S359A in separate tomato lines.
Analysis of the tomato lines overexpressing the wildtype BjHMGS1 revealed
that genes associated with production of the precursors of phytosterols,
carotenoids and vitamin E were upregulated. This caused an accumulation of
squalene and phytosterols, as well as á-tocopherol (vitamin E) and
carotenoids in tomato fruits. Moreover, tomato lines overexpressing the
S359A mutant BjHMGS1 bore fruits with even higher squalene and phytosterol
contents than the lines overexpressing the wildtype BjHMGS.
The manipulation of BjHMGS1 could be a promising strategy to increase
health-promoting squalene, phytosterols, á-tocopherol and carotenoids in