Transgenic Indian mustard overexpressing selenocysteine lyase or selenocysteine methyltransferase exhibit enhanced potential for selenium phytoremediation under field conditions

Two new transgenic Indian mustard [Brassica juncea (L.) Czern.] lines were tested under field conditions for their ability to accumulate selenium (Se)from Se- and boron-contaminated saline sediment. The transgenic lines overexpress genes encoding the enzymes selenocysteine lyase (cpSL) and selenocysteine methyltransferase (SMT), respectively. In the first Spring planting, cpSL, SMT, and wildtype plants (WT) were compared, while SMT and WT were compared in a second, Fall planting. In the Spring planting, shoots of the cpSL transgenic plants accumulated 2-fold more Se (p < 0.01), had 1.8 times higher leaf Se concentrations (p < 0.01), and grew better on contaminated soil than WT. The SMT plants had a 1.7-fold higher leaf Se concentration than WT (p < 0.05). In the Fall planting, the SMT transgenic plants accumulated 1.6-fold more Se in their shoots than WT (p < 0.01) with Se concentrations being higher in both leaves and stems. These results conclusively demonstrate that cpSL and SMT transgenic lines have significantly greater Se phytoremediation potential than wildtype Indian mustard. Further, this study confirms the importance of field testing for evaluating future transgenic lines.     

Field trial of transgenic Indian mustard plants shows enhanced phytoremediation of selenium-contaminated sediment

Three transgenic Indian mustard [Brassica juncea (L.) Czern.] lines were tested under field conditions for their ability to remove selenium (Se) from Se- and boron-contaminated saline sediment. The transgenic lines overexpressed genes encoding the enzymes adenosine triphosphate sulfurylase (APS), gamma-glutamyl-cysteine synthetase (ECS), and glutathione synthetase (GS), respectively. The APS, ECS, and GS transgenic plants accumulated 4.3, 2.8, and 2.3-fold more Se in their leaves than wild type, respectively (P < 0.05). GS plants significantly tolerated the contaminated soil better than wild type, attaining an aboveground biomass/area almost 80% of that of GS plants grown on clean soil, compared to 50% for wild type plants. This is the first report showing that plants genetically engineered for phytoremediation can perform successfully under field conditions.     

Effects of Ascorbic Acid Applied by Two Hydrocooling Methods on Physical and Chemical Properties of Green Leaf Lettuce Stored at 5°C

ABSTRACT: The effect of ascorbic acid applied by 2 hydrocooling methods on chemical and physical properties of'Waldmann's'dark green leaf lettuce ( Lactuca sativa L.) during cold storage was evaluated. Lettuce was immersed (in 1% ascorbic acid or tap water) or sprayed (with 1% ascorbic acid or tap water) or left untreated (control). Treatment solutions for immersion or spraying were applied at 5°C for 2 min. Afterward, lettuce was packaged in moisture impermeable plastic bags and stored at 5°C for up to 21 d. Analytical assays included total ascorbate content, 2,2'-azinobis (3-ethylbenz-thiazoline-6-sulphonic acid) (ABTS^˙+) Trolox equivalent antioxidant capacity, total phenolic content, relative water content and instrumental color. Lettuce was analyzed at 5 time intervals: before treatment application and at days 1, 7, 14, and 21 of storage time. Hydrocooling of leaf lettuce by immersion or spraying using 1% ascorbic acid solution increased total ascorbate content for up to 7 d, with an increase of more than 300% in total ascorbate content on day 1 compared with its initial value before treatments. However, the ABTS antioxidant capacity of leaf lettuce did not increase in ascorbic acid treated lettuce even though total ascorbate content increased. Ascorbic acid immersion was the only treatment that maintained the relative water content of leaf lettuce for 21 d. Further experimentation with the application of ascorbic acid during hydrocooling is needed to assess its usefulness as a processing treatment.