Abstract:

To reveal the main salicylic acid（SA）biosynthetic pathway in Rhizoctonia solani-infected Zoysia japonica,the key genes was recognized with aligned homologous sequences,the responsive pathway was identified according to transcriptional profile during pathogenesis,SA concentration was measured,and phenylalanine ammonia lyase（PAL）activity was verified. As typical alleles of PAL,genes ZjPAL1-ZjPAL5 were up-regulated continuously in the diseased root shown by their corresponding Unigenes,meaning an active response to infection at transcription level. About genes encoding isochorismate synthase,only ZjICS1 transcripts were observed,whose abundance was always less than one-tenth of that of ZjPAL1-ZjPAL5 and tended downwards with infection increasing. The PAL activity in the root reduced after mycelial invasion into the endodermis of the root. The more the activity was weakening,the faster the decrease of synthesized SA concentration was. However,the SA concentration in the non-infected leaves remained high by enhanced PAL activity. Phenylalanine pathway regulated by PAL gene plays a major role in SA synthesis when Z. japonica is infected by R. solani. Responsive intensity increases with the infection deepening,and the reduction of PAL activity will result in SA concentration decreasing.

Key words: Zoysia japonica, Rhizoctonia solani, salicylic acid synthesis, phenylalanine pathway