Botrytis elliptica Infection Induces LhSorPALs Expression in Lilium: Overexpression of LhSorPAL1 and LhSorPAL2 Enhances Disease Resistance via Phenylpropane Metabolite Accumulation

Phenylalanine ammonia-lyase (PAL) is the rate-limiting enzyme in the phenylpropane metabolic pathway, which is crucial for plant disease resistance. However, the functional roles of specific PAL members in lily defense against gray mold (Botrytis elliptica) remain unclear. Using the resistant lily cultivar ‘Sorbonne’, metabolomics analysis revealed that phenylpropane metabolites were significantly induced upon pathogen infection. Combined second- and third-generation transcriptome sequencing identified eight PAL family members. Among them, LhSorPAL1 and LhSorPAL2 were strongly induced by B. elliptica and were selected for further analysis. Both recombinant proteins exhibited PAL enzymatic activity catalyzing cinnamic acid production from L-phenylalanine. Overexpression of LhSorPAL1 or LhSorPAL2 in lily via Agrobacterium-mediated transformation had no obvious effect on plant growth but significantly increased the accumulation of lignin, flavonoids, and total phenols upon pathogen challenge, leading to enhanced resistance to gray mold. Conversely, antisense expression of LhSorPAL1 or LhSorPAL2 reduced the accumulation of these metabolites. Promoter analysis revealed that both LhSorPAL1pro and LhSorPAL2pro contain methyl jasmonate (MeJA)-, abscisic acid (ABA)-, and transcription factor-binding cis-elements. Collectively, these results demonstrate that LhSorPAL1 and LhSorPAL2 positively regulate lily resistance to B. elliptica by promoting phenylpropane metabolism, providing candidate genes for molecular breeding.