甜瓜粉霉病菌效应蛋白编码基因的预测与分析

 粉霉病是一种严重影响甜瓜果实品质并造成经济损失的采后病害,效应蛋白在病原真菌致病机制中发挥着重要作用。为获得引起甜瓜粉霉病病原菌粉红单端孢(Trichothecium roseum)的效应蛋白,本研究利用一系列生物信息分析软件(SignalP, TMHMM, Protcomp, big-PI Predictor, TargetP和Blastp)对该菌进行效应蛋白预测与分析,并采用实时荧光定量PCR检测其中6个候选效应蛋白编码基因在离体诱导培养和接种果实时的表达模式。结果表明:从T. roseum的9 760个蛋白序列中预测得到154个候选效应蛋白,其中64个具有功能注释,其余为功能未知蛋白;候选效应蛋白的信号肽长度在14~30 aa之间,且大部分是由信号肽酶I型进行识别;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;其中5个候选效应蛋白编码基因在离体诱导条件下和接种果实时表达量均显著升高,说明其可能为真正的效应蛋白。本研究预测获得了T. roseum中的效应蛋白,实时荧光定量PCR分析说明效应蛋白编码基因参与了T. roseum侵染甜瓜果实的致病过程,这些结果为进一步分析效应蛋白的功能与致病机制奠定了基础。

Genome-wide prediction and analysis of candidate effector-encoding genes in Trichothecium roseum

Pink rot, a postharvest disease caused by Trichothecium roseum, can seriously affect the quality of muskmelon fruit and cause significantly economic loss. Effectors are thought to play an important role in the pathogenesis of the pathogenic fungi. In order to understand the interactions of pathogen-muskmelon, the effectors of T. reseum were predicted and analyzed by the bioinformatics softwares (SignalP, TMHMM, Protcomp, big-PI Predictor, TargetP and Blastp). Furthermore, the expression patterns of 6 effector-encoding genes during the vegetative growth and fruit infection of the fungus were monitored by real-time fluorescence quantitative PCR. The results showed that 154 effector candidates were predicted from 9 760 protein sequences in T. roseum, of which only 64 had functional annotations. Additionally, the length of their signal peptides was ranged between 14~30 aa, and most of them belong to signal peptidase I-type. Meanwhile, the amino acids with the highest appearance frequency in signal peptides were alanine, leucine and serine. In addition, the expression of 5 candidate effector-encoding genes was significantly increased in in vitro-induced culture and during fruit infection, implying that those candidates may be real effectors. The prediction and real-time RT-PCR results in this study indicated that the effectors were involved in the pathogenesis of T. roseum on muskmelon fruit, laying the basis for further analysis of the effector function and pathogenesis in the fungus.