Time-course transcriptomic study of phenolic metabolism and P450 enzymes in Pinus massoniana Lamb. after feeding by Monochamus alternatus Hope

Pinus massoniana Lamb. is an economically important pioneer conifer in southern China. Monochamus alternatus is considered the vector insect of the Bursaphelenchus xylophilus, a nematode that can cause destructive pine wilt disease. Many phenolic compounds have been identified to play key roles in plant defense against biotic/abiotic damages in multiple ecosystems. In addition, the cytochrome p450 enzymes reportedly participate in various secondary metabolism pathways in plant. Surprisingly, however, no study has characterized putative phenolic defenses nor the P450 enzymes in P. massoniana inoculated by M. alternatus at the transcriptome level. Here, we compared changes in the whole transcriptome by RNA-Seq, finding that different expressed genes in phenolic biosynthetic related pathways were significantly enriched, indicating phenolic secondary metabolism in P. massoniana was activated after M. alternatus feeding. Using qRT-PCR, we then explored the changes of limiting enzyme genes in phenolic biosynthetic pathways during a series sampling time-point in both M. alternatus feeding treatment and control. Expression profile of target genes varied in their expression level, initial reaction time, peak time and reaction duration. This study provides a platform for better understanding molecular changes that could aid forest protection and breeding efforts to improve performance in the face of biotic damage.