凸脐蠕孢菌玉米、高粱专化型的细胞壁降解酶活性及基因表达分析
Activity analysis and gene expression of cell wall degradation enzymes in Setosphaeria turcica f. sp. zeae and S. turcica f. sp. sorghi

为探明玉米专化型和高粱专化型凸脐蠕孢菌的细胞壁降解酶在致病过程中的作用,采用酶活性检测方法测定了2种专化型的细胞壁降解酶活性,并检测了相关基因的表达。结果表明:高粱专化型凸脐蠕孢菌的聚甲基半乳糖醛酸酶(PMG)活性为115.84 U/mg,略高于玉米专化型;玉米专化型的多聚半乳糖醛酸酶(PG)和纤维素酶(Cx)的活性分别为151.76 U/mg和168.53 U/mg,略高于高粱专化型;且同一种专化型菌株的细胞壁降解酶活性存在差异。2种专化型的细胞壁降解酶基因表达量存在差异,Cx基因在2种专化型互作过程中均随病程的延长而大幅度上调表达;高粱专化型的PG基因随病程的延长大幅度上调表达,而玉米专化型的PG基因随病程的延长上调表达量有所下降;高粱专化型的PMG基因随病程的延长大幅度上调表达,而玉米专化型的PMG基因随病程的延长下调表达。推测产酶能力、基因表达和基因时间表达的差异可能是引起凸脐蠕孢菌专化型致病专化性的诱因之一。
In order to determine the activities of the cell wall degradation enzymes, the expressions of related genes, which were proved to play an important role in the pathogenic process of Setosphaeria turcica f. sp. zeae and S. turcica f. sp. sorghi, were examined by using general laboratory test method and RT-PCR, respectively. The results showed that the polymethylgalacturonase (PMG) activity of S. turcica f. sp. sorghi was 115.84 U/mg, which was slightly higher than 111.16 U/mg of S. turcica f. sp. zeae. The polygalacturonase (PG) and cellulase (Cx) activities of S. turcica f. sp. zeae were 151.76 U/mg and 168.53 U/mg, respectively, which were slightly higher than that of S. turcica f. sp. sorghi. The differences in the enzyme activities existed in the same formae speciales. There were differences in the expression of cell wall degradation enzymes genes. In the interaction of two formae speciales, the expression trends of Cx gene were significantly up-regulated during disease extension. The expression trends of PG gene of S. turcica f. sp. sorghi was significantly up-regulated during disease extension, and the relative up-regulated quantities of PG gene of S.turcica f.sp. zeae slightly declined during disease extension. The expression trends of PMG gene of S.turcica f.sp. sorghi were significantly up-regulated during disease extension, and PMG gene of S. turcica f. sp. zeae was down-regulated. It indicated that the factors might become one of the causes leading to pathogenic specialization in the formae speciales of S. turcica, including the differences derived from the enzyme production ability, gene expression and expression time in the interaction.