title: 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.
authors.affiliation: Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No12 Zhongguancun South Street, Beijing 100081, People's Republic of China.
authors.forename: Qing-Mao
authors.initials: QM
authors.lastname: Shang
authors.forename: Liang
authors.initials: L
authors.lastname: Li
authors.forename: Chun-Juan
authors.initials: CJ
authors.lastname: Dong
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000595:Amino Acid Sequence; D018553:Cucumis sativus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D020440:Gene Duplication; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family; D009928:Organ Specificity; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics*; D010802:Phylogeny; D035261:Plant Components, Aerial / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D010937:Plant Growth Regulators / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000235:genetics; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013312:Stress, Physiological; D020080:Tandem Repeat Sequences
chemical_list: D018744:DNA, Plant; D010937:Plant Growth Regulators; D010940:Plant Proteins; D000040:Abscisic Acid; D010650:Phenylalanine Ammonia-Lyase