芸薹属CesA基因家族在AC基因组中的进化及其多态性分析

Evolution and Polymorphism Analysis of the CesA Gene Family in the AC Genome of Brassica

植物细胞壁在保持细胞完整和维持功能等方面发挥了极其重要的作用,纤维素合成酶(CesA)基因家族编码了参与细胞壁多糖生物合成的许多酶。为了系统地了解CesA基因家族在芸薹属AC基因组的基本情况及CesA多态性与抗菌核病之间的关系,本研究利用拟南芥CesA1基因AT4G32410的蛋白种子序列对白菜、甘蓝和甘蓝型油菜全基因组数据进行全基因组水平CesA鉴定(E-value=0),基因结构域特征、生化特征、进化关系等的分析。从连续3年用牙签茎秆接种菌核病的甘蓝型油菜田间抗病性鉴定试验中,筛选出高抗病和高感病材料8份,克隆其C07染色体上的CesA基因片段,记为C07-BnaCesA,并进行序列多态性与抗病关联性分析。结果显示,在芸薹属AC基因组中共鉴定到78个CesA基因,其中白菜23个,甘蓝16个,甘蓝型油菜39个(A亚基因组20个,C亚基因组19个)。基于UPGMA法CesA蛋白系统进化树在遗传距离0.24处明显分成2大类。2000 bp启动子区预测到被转录因子(TFs)结合位点最多的TFs为BBR-BPC、ERF,14个CesA没有预测到TFs结合位点,在白菜和甘蓝杂交形成油菜的进化过程中,可能发生了基因沉默。在8份材料中C07-BnaCesA基因片段共鉴定到58个SNPs。芸薹属AC基因组CesA基因在进化过程中有的比较保守,C07-BnaCesA基因片段多态性与菌核病抗性没有强的关联性。

Plant cell wall plays an important role in maintaining cell integrity and function.Many enzymes involved in cell wall polysaccharide biosynthesis are encoded by the cellulase synthase(CesA)gene family.To systematically analyze the CesA gene family in the AC genome of Brassica and the relationship between CesA polymorphism and resistance to Sclerotinia infection.In this study,the protein sequence of Arabidopsis thaliana CesA gene(AT4 G32410)was used as a seed sequence to identify genome-wide level of CesA in B.rapa,B.oleracea,and B.napus(E-value=0).The gene domain characteristics,biochemical characteristics,and evolutionary relationships of the genes were also examined.Eight high-resistant and susceptible cultivars were identified after three consecutive years of in-field selection using toothpick stem inoculation of stalks with Sclerotinia.The CesA gene on the A10 chromosome,recorded as C07-BnaCesA,was amplified with PCR in order to analyse sequence polymorphism and resistance.78 CesA genes were identified in the AC genome of Brassica:23 in B.rapa,16 in B.oleracea,and 39 in B.napus(20 on the A sub-genome and 19 on the C sub-genome).The genes were classified into 2 classes by UPGMA method.The most frequently predicted TFs in the 2000 bp pro moter region were BBR-BPC and ERF.14 CesA genes do not have predicted transcription factors(TFs)and have therefore possibly undergone genetic silencing during evolution after cross-breeding between B.rapa and B.oleracea.Furthermore,58 SNPs on the fragment of C07-BnaCesA gene were discovered using the 8 cultivars.The CesA gene on the AC genome of Brassica was relatively conservative during evolution however,no strong correlation between genetic polymorphism of the fragment of C07-BnaCesA gene and Sclerotinia resistance.