Stk2, a Mitogen-Activated Protein Kinase from Setosphaeria turcica,Specifically Complements the Functions of the Fus3 and Kss1 of Saccharomyces cerevisiae in Filamentation,Invasive Growth,and Mating Behavior

Setosphaeria turcica, an essential phytopathogenic fungus, is the primary cause of serious yield losses in corn; however, its pathogenic mechanism is poorly understood. We cloned STK2, a newly discovered mitogen-activated protein kinase gene with a deduced amino acid sequence that is 96% identical to MAK2 from Phaeosphaeria nodorum, 56% identical to KSS1 and 57% identical to FUS3 from Saccharomyces cerevisiae. To deduce Stk2 function in S. turcica and to identify the genetic relationship between STK2 and KSS1/FUS3 from S. cerevisiae, a restructured vector containing the open reading frame of STK2 was transformed into a fus3/kss1 double deletion mutant of S. cerevisiae. The results show that the STK2 complementary strain clearly formed pseudohyphae and ascospores, and the strain grew on the surface of the medium after rinsing with sterile water and the characteristics of the complementary strain was the same as the wild-type strain. Moreover, STK2 complemented the function of KSS1 in filamentation and invasive growth, as well as the mating behavior of FUS3 in S. cerevisiae, however, its exact functions in S. turcica will be studied in the future research.     

玉米大斑病菌STK2的基因组定位、蛋白质结构预测及其表达

【目的】确定玉米大斑病菌STK2在基因组中的位置;解析目的蛋白质Stk2的结构特征;构建STK2真核表达载体,获得真核表达体系中的胞外分泌蛋白。【方法】利用生物信息学方法,确定STK2在玉米大斑病菌基因组中的确切位置,解析Stk2蛋白质的结构特征;根据STK2的ORF序列及真核表达载体pPIC9K的多克隆位点设计引物,构建真核表达载体,采用电击转化法将重组质粒转入宿主菌 GS115 中进行诱导表达,利用SDS-PAGE检测并鉴定目的蛋白质。【结果】玉米大斑病菌STK2的ID为91433,该基因位于scaffold_3正链的1561986-1563262位置;Stk2蛋白具有MAPK类蛋白激酶的特征性保守结构域,其二级结构主要以α螺旋和无规则卷曲为主,β折叠较少且主要存在于N端,其三级结构具有1个较小的N端域和1个较大的C端域;成功构建了STK2的真核表达载体pPIC9K-STK2,筛选获得了抗性转化子;在毕赤酵母菌中,经甲醇诱导得到了1个分子量约为41 kD的蛋白质组分且被分泌至胞外,该蛋白质的大小与理论分子量相符,推测Stk2蛋白已在宿主菌中表达并被分泌至胞外。【结论】玉米大斑病菌STK2位于scaffold_3正链的1561986-1563262位置;Stk2具有MAPK激酶的所有特征性保守结构域,属于典型的MAPK蛋白激酶;该基因能在真核细胞中表达,获得了可溶性分泌蛋白质,为Stk2蛋白的多克隆抗体制备及基因的功能研究奠定基础。     

高渗胁迫对玉米大斑病菌生长发育及STK1表达的影响

【目的】观测高渗胁迫对玉米大斑病菌（Setosphaeria turcica）生长发育的影响,探讨甘油是否为病菌细胞中的渗透调节物质,分析STK1在高渗胁迫下的表达规律。【方法】采用2种高渗胁迫条件处理玉米大斑病菌,分析高渗胁迫对病菌生长发育的影响;检测高渗胁迫下菌丝细胞中甘油含量的变化,明确甘油是否为病菌中的渗透调节物质;利用半定量RT-PCR方法,分析高渗胁迫条件下STK1表达规律。【结果】玉米大斑病菌菌丝细胞的等渗液浓度为0.78 mol•L-1;在高渗胁迫条件下,菌落颜色均发生显著变化。1 mol•L-1 NaCl处理后菌落呈红褐色,菌落的生长速率也受到到明显的抑制;在1 mol•L-1NaCl胁迫下菌丝细胞中原生质体浓缩,出现明显的浓缩颗粒;随胁迫时间的延长和渗透胁迫物质浓度的增加,细胞中甘油含量显著增加;STK1在高渗胁迫48 h内表达量稳定增加。【结论】高渗胁迫抑制玉米大斑病菌菌落生长,改变菌落颜色,使菌丝细胞中原生质体高度浓缩,部分菌丝膨大呈球状;甘油是病菌细胞中的一种渗透调节物质;STK1参与调控病菌的渗透胁迫反应。