白叶枯病是仅次于稻瘟病的水稻第二大病害,Xa21是最早发现的白叶枯病抗性基因,其无毒基因ax21(ac-tivator of XA21-mediated immunity)在2009年底才被确定。Ax21为194个氨基酸的蛋白质,包含外泌信号肽,活性17肽,后续多肽链3个部分。推测其活性17肽与水稻细胞膜上的Xa21蛋白LRR结构域结合,启动水稻细胞下游磷酸化反应,引发水稻抗性。Ax21是革兰氏阴性菌中发现的首个介导调控运动、生物膜形成和毒力相关基因表达的群体感应因子。综述了近2年Ax21的结构、表达调控和生物学功能等方面的研究结果。
Sulfate can be activated by ATP sulfurylase and adenosine 5'-phosphosulfate kinase(APSK) in vivo. Recent studies suggested that APSK in Arabidopsis thaliana regulated the partition between APS reduction and phosphorylation and its activity can be modulated by cellular redox status. In order to study regulation of APSK in rice(Os APSK), Os APSK1 gene was cloned and its activity was analyzed. Os APSK1 C36 and C69 were found to be the conserved counterparts of C86 and C119, which involved in disulfide formation in At APSK. C36A/C69 A Os APSK1 double mutation was made by site directed mutagenesis. Os APSK1 and its mutant were prokaryotically over-expressed and purified, and then assayed for APS phosphorylation activity. Os APSK1 activity was depressed by oxidized glutathione, while the activity of its mutant was not. Further studies in the case that oxidative stress will fluctuate in vivo 3'-phosphoadenosine-5'-phosphosulfate content, and all APSK isoenzymes have similar regulation patterns are necessary to be performed.
Wang De-zhenChen Guo-guoLu Lu-jiaJiang Zhao-junRao Yu-chunSun Mei-hao
