Metabolic engineering of soybean affords improved phytosterol seed traits
Article first published online: 9 MAY 2011
© 2011 The Authors. Plant Biotechnology Journal © 2011 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd
Plant Biotechnology Journal
Volume 10, Issue 1, pages 12–19, January 2012
How to Cite
Neelakandan, A. K., Chamala, S., Valliyodan, B., Nes, W. D. and Nguyen, H. T. (2012), Metabolic engineering of soybean affords improved phytosterol seed traits. Plant Biotechnology Journal, 10: 12–19. doi: 10.1111/j.1467-7652.2011.00623.x
- Issue published online: 6 DEC 2011
- Article first published online: 9 MAY 2011
- Received 6 July 2010; revised 15 March 2011; accepted 15 March 2011.
- sterol 24-C-methyltransferase;
- phytosterol biosynthesis;
- seed-specific Promoter;
- transgenic seed;
Different combinations of three rate-limiting enzymes in phytosterol biosynthesis, the Arabidopsis thaliana hydroxyl methylglutaryl CoA1 (HMGR1) catalytic subunit linked to either constitutive or seed-specific β-conglycinin promoter, and the Glycine max sterol methyltransferase1 (SMT1) and sterol methyltransferase2-2 (SMT2-2) genes, under the control of seed-specific Glycinin-1 and Beta-phaseolin promoters, respectively, were engineered in soybean plants. Mature seeds of transgenic plants displayed modest increases in total sterol content, which points towards a tight control of phytosterol biosynthesis. However, in contrast to wild-type seeds that accumulated about 35% of the total sterol in the form of intermediates, in the engineered seeds driven by a seed-specific promoter, metabolic flux was directed to Δ5-24-alkyl sterol formation (99% of total sterol). The engineered effect of end-product sterol (sitosterol, campesterol, and stigmasterol) over-production in soybean seeds resulted in an approximately 30% increase in overall sitosterol synthesis, a desirable trait for oilseeds and human health. In contradistinction, increased accumulation of cycloartenol and 24(28)-methylencylartanol (55% of the total sterol) was detected in plants harbouring the constitutive t-HMGR1 gene, consistent with the previous studies. Our results support the possibility that metabolic flux of the phytosterol family pathway is differentially regulated in leaves and seeds.