Comparative study on the mRNA expression of Pinus massoniana infected by Bursaphelenchus xylophilus

Pine wilt disease(PWD)is a devastating disease affecting the growth of Pinus massoniana,often leading to withering and death.To reveal the changes involved during disease progression,we investigated the mRNA expression profile of P.massoniana infested by Bursaphelenchus xylophilus.The infestation resulted in the downregulation of genes involved in interactions with pathogenic pathways such as disease resistance gene,CC-NBS-LRR resistancelike protein,and the gene encoding a putative nematode resistance protein.Increased infestation pressure(number of nematodes inoculated)caused a continuous decline in the gene expression of stem samples.An infestation of P.massoniana also resulted in a pathway enrichment of genes involved in phenylpropanoid metabolism and flavonoid biosynthesis,which in turn reduced the levels of total phenols and total flavonoids.A downregulation of auxin responsive family protein was observed in infested samples,which resulted in a suppression of plant growth.Thus,upon B.xylophilus infestation,a downregulation of genes associated with the recognition of pathogens,PWD resistance,and growth regulation was observed in P.massoniana,together with a decrease in the levels of phytoalexinlike secondary substances,all of which resulted in withering and ultimately death of P.massoniana.