Comprehensive, Genome-Wide Identification and Expression Analyses of Phenylalanine Ammonia-Lyase Family under Abiotic Stresses in Brassica oleracea

Abstract

Phenylalanine ammonia-lyase (PAL) acts as the rate-limiting enzyme for anthocyanin biosynthesis through the phenylpropanoid pathway, a crucial component of plant secondary metabolism. The <i>PAL</i> gene family plays a crucial role in plants' defense and stress responses, but its in silico identification and expression analyses in <i>Brassica oleracea</i> under different abiotic stresses remain unexplored. In this study, nine <i>BolPAL</i>, seven <i>BrPAL</i>, four <i>AtPAL</i>, and seventeen <i>BnPAL</i> genes were obtained from the genomes of <i>B. oleracea</i>, <i>Brassica rapa</i>, <i>Arabidopsis thaliana</i>, and <i>Brassica napus</i>, respectively. Segmental duplication and purifying selection are the causes of the <i>BolPAL</i> gene's amplification and evolution. The <i>BolPAL</i> genes with comparable intron-exon architectures and motifs were grouped together in the same clade. Three categories comprised the <i>cis</i>-regulatory elements: abiotic stressors, phytohormones, and light. According to the results of the qRT-PCR experiments, the majority of the <i>BolPAL</i> genes were expressed highly under MeJA, a low temperature, and a high temperature, and they were downregulated under ABA. Under white light (100 µmol m^-2 s^-1) with 50, 100, or 150 µmol m^-2 s^-1 far-red (FR), only a small number of the <i>PAL</i> genes were expressed at 50 and 100 µmol m^-2 s^-1 FR, while the majority of the <i>PAL</i> genes were slightly elevated at 150 µmol m^-2 s^-1 FR. This work offers a theoretical foundation for molecular breeding research to investigate the role of <i>BolPAL</i> genes and their role in anthocyanin biosynthesis.