Characterization of the Genes for Sulfate Activation from Higher Plants

9408031 Leustek两种酶，三磷酸腺苷硫酰基酶和碱性磷酸酶激酶，催化植物中硫酸盐的活化，从而合成对细胞功能至关重要的含硫化合物。在叶绿体、线粒体和细胞质中，三磷酸腺苷硫酰化酶同工酶被划分为不同的区划，这表明它们可能在硫代谢中发挥不同的生理作用。本研究的目的是研究这些同工酶的表达，为控制硫酸盐的活化奠定分子基础。利用酿酒酵母ATP硫酰化酶(Met3)或APS激酶(Met14)突变体的互补作用，从拟南芥中克隆了硫酸盐激活酶的编码基因。目前已分离到四个三磷酸腺苷硫酰基酶基因家族成员和一个编码APS激酶的成员。这些基因在拟南芥和芥菜中的表达和功能有待进一步研究。由于含硫肽对重金属的抗性起着重要的作用，因此将研究重金属暴露对ATP硫酰基酶和APS激酶表达的影响。这些研究将有助于加深我们对植物新陈代谢、生长发育和对逆境反应的了解。***

9408031 Leustek Two enzymes, ATP sulfurylase and APS kinase, catalyze the activation of sulfate in plants leading to the synthesis of sulfur containing compounds vital for cell function. Isoenzymes of ATP sulfurylase are compartmentalized in chloroplasts, mitochondria and the cytosol, suggesting that they may play distinct physiological roles in sulfur metabolism. The objective of this research is to study the expression of the isoenzymes in order to establish a molecular basis for the control of sulfate activation. cDNAs encoding the sulfate activating enzymes were cloned from Arabidopsis thaliana by complementation of Saccharomyces cerevisiae ATP sulfurylase, met3, or APS kinase, met14, mutants. Four members of the ATP sulfurylase gene family and one encoding APS kinase have been isolated. It is proposed to further characterize these cDNAs and to study their expression and function in A. thaliana and Brassica juncea. Since sulfur-containing peptides play a significant role in resistance to heavy metals, the influence of heavy metal exposure will be investigated on expression of ATP sulfurylase and APS kinase. These studies will help advance our understanding of plant metabolism, growth, development and response to stress. ***