Effects of different exogenous selenium on Se accumulation, nutrition quality, elements uptake, and antioxidant response in the hyperaccumulation plant Cardamine violifolia.

Cardamine violifolia (Brassicaceae) is a novel selenium(Se) hyperaccumulation plant with rich nutrients, and serves as a good source of special vegetables in Enshi, China. The present study aimed to investigate the effects of the application of selenate, selenite, and Se yeast (50-800 mg/L) on the growth, Se accumulation, nutrient uptake, and antioxidant response of C. violifolia. The results showed that the Se accumulation efficiency was selenate > selenite > Se yeast, the maximum Se concentration could achieve over 7000 mg/kg, and about 90% was organic Se. The major Se speciation found was mainly SeCys2 and the proportion of various Se species were affected by the Se forms and concentrations. Besides, the plant growth, nutrition quality indexes, element uptakes, and antioxidant responses indicated that 200 mg/L selenate was optimum for C. violifolia to accumulate Se without much impacts, while to obtain more proportion of organic Se, 200 mg/L selenite might be a better choice.

Molecular cloning and characterization of a KCS gene from Cardamine graeca and its heterologous expression in Brassica oilseeds to engineer high nervonic acid oils for potential medical and industrial use.

Nervonic acid 24:1 Delta15 (cis-tetracos-15-enoic acid) is a very long-chain monounsaturated fatty acid and exists in nature as an elongation product of oleic acid. There is an increasing interest in production of high nervonic acid oils for pharmaceutical, nutraceutical and industrial applications. Using a polymerase chain reaction approach, we have isolated a gene from Cardamine graeca L., which encodes a 3-ketoacyl-CoA synthase (KCS), the first component of the elongation complex involved in synthesis of nervonic acid. Expression of the Cardamine KCS in yeast resulted in biosynthesis of nervonic acid, which is not normally present in yeast cells. We transformed Arabidopsis and Brassica carinata with the Cardamine KCS under the control of the seed-specific promoter, napin. The T(3) generations of transgenic Arabidopsis and B. carinata plants expressing the Cardamine KCS showed that seed-specific expression resulted in relatively large comparative increases in nervonic acid proportions in Arabidopsis seed oil, and 15-fold increase in nervonic acid proportions in B. carinata seed oil. The highest nervonic acid level in transgenic B. carinata lines reached 44%, with only 6% of residual erucic acid. In contrast, similar transgenic expression of the Cardamine KCS in high erucic B. napus resulted in 30% nervonic acid but with 20% residual erucic acid. Experiments using the Lunaria KCS gene gave results similar to the latter. In both cases, the erucic acid content is too high for human or animal consumption. Thus, the Cardamine KCS: B. carinata high nervonic/highly reduced erucic transgenic seed oils will be the most suitable for testing in pharmaceutical/nutraceutical applications to improve human and animal health.