A hypocotyl-derived somatic embryogenic system in Brassica juncea Czern & Coss and its manipulation for enhanced storage lipid accumulation

A simple and reproducible protocol for induction, growth and development of somatic embryos from hypocotyl explants of Indian mustard (Brassica juncea L. Czern & Coss) var. RLM 198 is reported. The HDSE (Hypocotyl derived som atic embryos) were fleshy globular to torpedo structures that, were maintai ned by regular subculturing every three weeks. These embryos developed non- synchronously into the heart shaped-stage while some were matured into a gr een cotyledon-stage bearing embryos in the same medium. The HDSE accumulate d as much as 50.2% lipid content on a dry weight basis at 14 DAC (days afte r culture) using a culture medium supplemented with 10% PEG (Polyethylene g lycol 6000) in comparison to less than 15% lipid content in 2% sucrose (con trol) or 20 muM ABA (abscisic acid). An increase in total soluble sugar con tent was observed with 2.5% PEG and increasing PEG concentration caused a d ecrease in their contents in HDSE. The activities of invertase, acetyl CoA carboxylase and 1-C-14-acetate incorporation into lipids in HDSE were enhan ced significantly in the culture medium containing 10% PEG. The content of triacylglycerols in HDSE was maximum with 10% PEG supplemented culture medi um. The wax content in HDSE increased progressively with an increase of PEG concentration in the culture medium. The ABA and PEG supplementation incre ased the content of membrane lipids when the data was expressed on a 100 g dry weight basis. The proportion of palmitate acid erucate decreased and th at of oleate, linoleate and linolenate increased at 14 DAC in HDSE in 10% P EG supplemented culture medium. Thus, the manipulation of culture condition s significantly altered total lipid content, membrane lipid composition and the quality of storage lipids.