Multiple tandem duplication of the phenylalanine ammonia-lyase genes in Cucumis sativus L.

Abstract

Phenylalanine ammonia-lyase (PAL) is the first entry enzyme of the phenylpropanoid pathway, and therefore plays a key role in both plant development and stress defense. In many plants, PAL is encoded by a multi-gene family, and each member is differentially regulated in response to environmental stimuli. In the present study, we report that PAL in cucumber (Cucumis sativus L.) is encoded for by a family of seven genes (designated as CsPAL1-7). All seven CsPALs are arranged in tandem in two duplication blocks, which are located on chromosomes 4 and 6, respectively. The cDNA and protein sequences of the CsPALs share an overall high identity to each other. Homology modeling reveals similarities in their protein structures, besides several slight differences, implying the different activities in conversion of phenylalanine. Phylogenic analysis places CsPAL1-7 in a separate cluster rather than clustering with other plant PALs. Analyses of expression profiles in different cucumber tissues or in response to various stress or plant hormone treatments indicate that CsPAL1-7 play redundant, but divergent roles in cucumber development and stress response. This is consistent with our finding that CsPALs possess overlapping but different cis-elements in their promoter regions. Finally, several duplication events are discussed to explain the evolution of the cucumber PAL genes.

Rice phenylalanine ammonia-lyase gene OsPAL4 is associated with broad spectrum disease resistance

“…The organization of rice OsPAL gene clusters on chromosomes 2 and 4 is consistent with the organization of similar PAL gene members on chromosomes of potato (Trognitz et al 2002), wheat (Liao et al 1996) and cucumber (Shang et al 2012). Phylogenetic analysis shows that barley PAL proteins are organized into multiple groups similar to rice OsPALs, suggesting that some of the gene duplication events at these loci predate the divergence of clades containing these two monocots, but after monocots diverged from dicots (Fig.…”

Identification of phenylpropanoid biosynthetic genes and phenylpropanoid accumulation by transcriptome analysis of Lycium chinense

“…The gene expression analysis showed that the expression level of LcPAL in green fruits was also high; however, the content of its metabolites in green fruits was very low. This is probably owing to the fact that PAL s are codified by a multigene family in plants [26, 27], suggesting the existence of other PAL isoforms in green fruits. In previous study of our laboratory, the expression of C4H in different organs was diverse between different species.…”

Early Phenylpropanoid Biosynthetic Steps in Cannabis sativa: Link between Genes and Metabolites

“…Interestingly, specific functions, although partially overlapped, characterize PAL family members even in species where they clusterize strictly. A clear example derives from the deep investigation on the seven PAL genes of Cucumis sativus where a pattern of gene expression (tissue and stress responsive) specific for the different members has been highlighted [20]. …”