梨Ⅲ型聚酮合成酶家族的比较基因组学研究及表达模式分析

Comparative genomics study of type Ⅲ polyketide synthase family of pear and its expression pattern analysis

植物Ⅲ型聚酮合成酶(PKS Ⅲ)在植物次生代谢产物生物合成中起着非常重要的作用。本研究从7种蔷薇科果树中共鉴定出57个PKS家族成员,随后进行种间比较基因组学分析。基因结构和保守基序分析表明,57个PKS多数由两个外显子和一个内含子组成,都具有PKS特有的保守结构域Chal-sti-synt-N和Chal-sti-synt-C。进化分析显示,57个PKS可明显分为4个亚家族,其中I亚家族成员数目最多。染色体定位及基因复制事件表明,PKS不均匀地分布在2~5条染色体上,且PKS家族进化过程主要受纯化选择作用。荧光定量分析发现,PbPKS4和PbPKS5表达模式与‘砀山酥梨’(Pyrus bretschneideri cv.‘Dangshan Su’)不同发育时期果实中木质素及石细胞含量变化趋势类似,因此推测这2个基因在梨果实木质素合成及石细胞发育过程中发挥一定作用。本研究为今后研究蔷薇科果树PKS家族建立了基础,也为从分子水平改善梨果实品质提供了理论依据。

Type Ⅲ polyketide synthase（PKS） plays an important role in the biosynthesis of secondary metabolites in plants.In this study,a total of 57 PKS family members were identified from 7 species of fruit trees in family Rosaceae,followed by a comparative genome analysis.Analysis of gene structure and conserved motifs showed that most of these PKSs were composed of two exons and one intron,containing the PKS-specific conserved domains Chal-sti-synt-N and Chal-sti-synt-C.Phylogenetic analysis showed that 57 PKSs were divided into four subfamilies with the maximal number in the subfamily I.And chromosomal location analysis showed that PKSs were unevenly distributed across chromosomes 2 to 5.Furthermore,it was found that the evolution of PKS family was mainly affected by the purification and selection under gene-duplication analysis.Fluorescence quantitative analysis showed that the expression patterns of Pb PKS4 and Pb PKS5 were in a similar trend to the change in both lignin and stone cell contents at the different developmental stages of Pyrus bretschneideri cv.‘Dangshan Su＇.Therefore,both of Pb PKS4 and Pb PKS5 might be associated with the lignin synthesis and stone cell development in fruits of P.bretschneideri cv.‘Dangshan Su＇.These results primarily reveal the important function of PKSs in lignin metabolism in some Rosaceae species,and provide a theoretical foundation for improving the quality of pear fruits at the molecular level.