The Critical Role of Phenylpropanoid Biosynthesis Pathway in Lily Resistance Against Gray Mold.

Gray mold caused by is one of the most determinative factors of lily growth and has become a major threat to lily productivity. However, the nature of the lily interaction remains largely unknown. Here, comparative transcriptomic and metabolomic were used to investigate the defense responses of resistant ('Sorbonne') and susceptible ('Tresor') lily cultivars to infection at 24 hpi. In total, 1326 metabolites were identified in 'Sorbonne' and 'Tresor' after infection, including a large number of phenylpropanoids. Specifically, the accumulation of four phenylpropanes, including eriodictyol, hesperetin, ferulic acid, and sinapyl alcohol, was significantly upregulated in the -infected 'Sorbonne' compared with the infected 'Tresor', and these phenylpropanes could significantly inhibit growth. At the transcript level, higher expression levels of , , and led to a higher content of resistance-related phenylpropanes (eriodictyol, ferulic acid, and sinapyl alcohol) in 'Sorbonne' following infection. It can be assumed that these phenylpropanes cause the resistance difference between 'Sorbonne' and 'Tresor', and could be the potential marker metabolites for gray mold resistance in the lily. Further transcriptional regulatory network analysis suggested that members of the AP2/ERF, WRKY, Trihelix, and MADS-M-type families positively regulated the biosynthesis of resistance-related phenylpropanes. Additionally, the expression patterns of genes involved in phenylpropanoid biosynthesis were confirmed using qRT-PCR. Therefore, we speculate that the degree of gray mold resistance in the lily is closely related to the contents of phenylpropanes and the transcript levels of the genes in the phenylpropanoid biosynthesis pathway. Our results not only improve our understanding of the lily's resistance mechanisms against , but also facilitate the genetic improvement of lily cultivars with gray mold resistance.