Genome-Wide Identification of the PAL Gene Family in Idesia polycarpa and Transcriptomic Responses to Botryosphaeria dothidea Infection
TL;DR
Findings demonstrate time- and gene-specific IpPAL responses to B. dothidea and identify candidate genes for further functional analysis.
Abstract
Idesia polycarpa is a woody oil tree threatened by stem canker caused by Botryosphaeria dothidea, yet the organization and infection-responsive behavior of its phenylalanine ammonia-lyase (PAL) gene family remain poorly understood. Here, we identified five IpPAL genes and characterized their phylogenetic relationships, conserved features, duplication patterns, promoter cis-elements, and infection-associated expression profiles. Segmental and tandem duplication contributed to IpPAL family evolution, and all duplicated pairs showed Ka/Ks ratios below 1, consistent with purifying selection. RNA sequencing (RNA-seq) of contrasting Chengdu and Zhangjiajie provenances revealed distinct temporal responses. In Chengdu, IpPAL2–IpPAL4 were significantly upregulated at 24 h after inoculation, whereas all five genes were upregulated at 96 h. In Zhangjiajie, all five IpPAL genes were significantly upregulated at 24 h, while IpPAL2–IpPAL5 remained upregulated at 96 h. No IpPAL gene met the differential-expression criteria between provenances under mock conditions or at 24 h; at 96 h, IpPAL1 and IpPAL3 were lower and IpPAL5 was higher in Zhangjiajie than in Chengdu. Scanning electron microscopy (SEM) provided complementary qualitative evidence of provenance-associated tissue responses. These findings demonstrate time- and gene-specific IpPAL responses to B. dothidea and identify candidate genes for further functional analysis.