玉米弯孢叶斑病菌全基因组分泌蛋白的预测与分析
Genome-wide prediction and analysis of the classical secreted proteins of Curvularia lunata

为深入了解玉米弯孢叶斑病菌致病的分子机制,采用信号肽分析软件SignalP 4.1与PSORTb 3.0.2、跨膜螺旋结构分析软件TMHMM 2.0与THUMBUP、GPI锚定位点分析软件big-PI Predictor和亚细胞器蛋白定位分析软件TargetP 1.1这6款软件综合预测该菌全基因组中10372条蛋白序列,并对筛选出的分泌蛋白信号肽基本特征进行分析。结果表明,在玉米弯孢叶斑病菌全基因组编码蛋白中共发现804个具有典型信号肽的分泌蛋白,占全基因组蛋白总数的7.8%;编码这些蛋白的开放阅读框最小为219 bp,最大为7113 bp,平均为1252 bp;引导它们的信号肽长度分布在13~37 aa之间,平均为19 aa。信号肽中出现频率最高的氨基酸依次为丙氨酸、亮氨酸和丝氨酸。信号肽切割位点与根癌土壤杆菌、粗糙脉孢霉和马铃薯晚疫病菌一样,同属于A-X-A型。70个具有功能描述的分泌蛋白主要是和细胞代谢与转运、信号转导有关的酶类;还有一些降解细胞壁组分及与致病相关的酶类,可能与玉米弯孢叶斑病菌的毒性有关。
In order to have a further understanding of the molecular mechanism of pathogenesis, 10 372 protein sequences of Curvularia lunata were analyzed by using the signal peptide prediction algorithms SignalP 4.1 and PSORTb 3.0.2, transmembrane helix prediction algorithms TMHMM 2.0 and THUMBUP, GPI-anchoring site prediction algorithm big-PI Predictor, and subcellular protein location prediction algorithm TargetP 1.1. Meanwhile, the basic features of signal peptides in prediction results were statistically analyzed. As a result, 804 secreted proteins were found, accounting for 7.8% of the total number. For these proteins, the minimum and maximum of the open read frames were 219 bp and 7 113 bp, respectively, and the mean score was 1 252 bp. The distribution of length was concentrated in 13-37 amino acids and the average length was 19 amino acids. The top three frequent amino acids in signal peptides were alanine, leucine and serine. The signal peptide cleavage site belonged to A-X-A type, which was consistent with other secreted proteins from Agrobacterium tumefaciens, Neurospora crassa and Phytophthora infestans. Among these, the functions of the 70 secreted proteins had been described previously. Many of them were involved in cellular metabolism and signal transduction, etc. In addition, some of the secreted proteins were functionally related to cell wall-degrading and pathogenicity, which were likely to be associated with the virulence of C. lunata.