拟南芥抗凋亡突变体fbr136的分离鉴定与分析

Identification and Characterization of The Arabidopsis fumonisin B_1 resistant fbr136

植物细胞程序性死亡(programmed cell death,PCD)在植物的生长发育进程以及防御生物与非生物胁迫的过程中具有重要的作用.Fumonisin B1(FB1)是一种真菌毒素,是鞘脂生物合成途径中关键酶神经酰胺合酶(ceramide synthase)的竞争性抑制剂.FB1在动植物细胞中均能够诱导PCD.为了探索植物PCD的机制,通过筛选拟南芥抗FB1的突变体,分离鉴定了11个fumonisin B1resistant(fbr)突变体.遗传分析表明,这些突变体分别是由9个相同或者不同的遗传座位突变造成的.对其中一个代表性的突变体fbr136进行了详细的表型分析和初步遗传定位.fbr136对其他PCD诱导剂,例如H2O2或paraquat也表现出一定的抗性或耐受性,而且在fbr136突变体中FB1不能正常诱导PR1基因的表达,说明fbr136突变体PCD的发生可能受到阻碍.硝基四唑(Nitroblue tetrazolium,NBT)染色表明,FB1处理fbr136突变体后产生和积累活性氧(reactive oxygenspecies)比野生型植物显著降低,暗示其抗凋亡表型可能与活性氧的产生有关.推测FBR136可能是FB1在诱导PCD过程中,从鞘脂含量变化到活性氧积累变化这一途径的一个重要的调控因子.fbr136被定位于染色体Ⅲ上,与以往鉴定的抗FB1突变基因的定位都不同,因此,FBR136可能是FB1诱导PCD信号途径中的一个新基因.

Plant programmed cell death （PCD） plays an important role in plant growth and development as well as defensive response against biotic and abiotic stresses. Fumonisin B1 （FB1） is a fungi toxin, which is a competitive inhibitor of ceramide synthase in de novo sphingolipid biosynthesis. FB1 can induce PCD in both animal and plant cells. To dissect this pathway, a genetic screen for fumonisin BI resistant （fbr） mutants, and identified 11 fbr mutants was carried out. Genetic analysis showed that these 11 mutants belonged to 9 complementary groups or genetic loci. Here a detailed phenotypic analysis of fbr136 was reported. In addition to the resistance to FB1,fbr136 also showed resistance other PCD-inducing compounds, including H2O2 and paraquat. Furthermore, FB1-induced PR1 expression was reduced in jbr136, suggesting that a PCD pathway is likely impaired in the mutant. When stained with nitroblue tetrazolium （NBT）, jbr136 showed a reduced accumulation of reactive oxygen species （ROS） induced by FB1. The fbr136 mutation was roughly mapped onto chromosome Ⅲ, where no other fbr mutants have been previously identified. It is proposed that FBR136 may act as an important regulator in a sphingolipid-mediated PCD pathway, involved in the generation of ROS.