CAREER: Genetic Engineering Approaches for the in Vivo Study of Plant Metabolism of Selenium and Other Oxyanions

植物中的硒(Se)和硫的代谢被认为利用相同的酶。这位研究者以前的研究表明，参与硫酸盐还原的ATP硫酰基酶的过度表达促进了硒的还原，并导致有机硒的积累。该项目的目标是查明更多控制植物中Se通量的酶，并阐明硫酸盐同化酶在相关元素碲、钼和钨的吸收和还原中的任何参与。硒半胱氨酸似乎是硒分配到蛋白质(有毒)、挥发性形式或各种累积形式中的控制点。通过两种酶的过度表达，将产生两种不同的Se“汇”：一种是低毒的、不可溶的元素Se，另一种是低毒的挥发性Se。这些新的Se汇对植物中Se通量的影响将通过测量转基因植物积累的Se的形式以及通过测量它们对Se的耐性、积累和挥发来测试。为了研究两种酶同时过表达对途径的影响，将不同的转基因进行杂交，并研究双转基因中的Se通量。该项目的另一个目标是验证硫酸盐同化途径也参与了碲酸盐、钼酸盐和钨酸盐的吸收和还原这一假设。为此，将分析过表达与硫酸盐/硒酸盐吸收和还原有关的酶的现有转基因印度芥菜(Brassica Jiea)对碲、钼和钨的耐受性和积累，以及这些元素的积累形式。这些研究产生的新信息可用于对代谢特性发生变化的植物进行遗传操作，例如增加或减少微量元素积累。这一点很重要，因为这些元素具有环境和/或医学上的重要性，如污染物、微量营养素等。这一职业项目的一个重要部分将是开发一门关于利用植物清理环境(植物修复)的研究生课程和一门高级植物生理学课程。这些课程将旨在最大限度地利用多媒体和在线资源。

Selenium (Se) and sulfur metabolism in plants are thought to make use of the same enzymes. Previous studies by this investigator have shown that overexpression of ATP sulfurylase (involved in sulfate reduction) promotes selenate reduction and leads to accumulation of organic selenium. The goals of this project are to pinpoint more enzymes that are rate-controlling for Se fluxes in plants, and to clarify any involvement of the sulfate assimilation enzymes in uptake and reduction of the related elements tellurium, molybdenum, and tungsten. Selenocysteine appears to be a control point for Se allocation into proteins (toxic), into volatile forms, or into various accumulated forms. By overexpression of two enzymes, two different Se "sinks" will be created: one as low-toxic, insoluble elemental Se, the other as low-toxic volatile Se. The effects of these new Se sinks on the Se fluxes in the plant will be tested by measuring the forms of Se accumulated by the transgenic plants, and by measuring their Se tolerance, accumulation and volatilization. To study the effect of simultaneous overexpression of two enzymes in the pathway, different transgenics will be crossed and the Se fluxes in the double-transgenics studied. The other objective of this project is to test the hypothesis that the sulfate assimilation pathway is also involved in uptake and reduction of tellurate, molybdate, and tungstate. To this end, available transgenic Indian mustard plants (Brassica juncea) that overexpress enzymes involved in uptake and reduction of sulfate/selenate will be analyzed for tolerance and accumulation of tellurium, molybdenum and tungsten, and for the accumulated forms of these elements. The new information generated by these studies may be employed for the genetic manipulation of plants with altered metabolic properties, e.g. with enhanced or reduced trace element accumulation. This is of significance since these elements are of environmental and/or medical importance, as pollutants, micronutrients, etc. An essential part of this CAREER project will be the development of a graduate course on environmental cleanup using plants (phytoremediation) and a senior-level plant physiology course. These courses will be designed to make optimal use of multimedia and on-line resources.