杜鹃花科质体基因组结构及系统发育分析

Plastid Genome Structural Characteristics and Phylogenetic Relationships of Ericaceae

为解析杜鹃花科质体基因结构特征,并澄清杜鹃花科内部的系统发育关系,利用Genbank数据库已公开发表的杜鹃花科13属51个物种的质体基因组数据,对其基因组大小、重复序列等进行统计分析,并采用最大似然法和贝叶斯推断重建其系统发育树。结果显示:(1)异养类群的质体基因组大小为26~40 kb,自养类群的为150~230 kb,二者差异显著;非杜鹃属物种的基因组大小为150~195 kb,杜鹃属物种的为152~230 kp,二者差异显著。(2)简单重复序列(SSRs)、串联重复序列和散在重复序列在异养和自养类群间、非杜鹃属和杜鹃属物种间差异均显著。(3)杜鹃花科的系统发育关系分析表明,支持率≥95%的分支占总分支数目的87%,杜鹃花科为单系类群,草莓树亚科和水晶兰亚科为姐妹群,二者与鹿蹄草亚科形成的分支为较早分化的类群,越橘亚科和Ericoideae为姐妹群。草莓树亚科除外(仅包括一个种),其余4个亚科均为单系。属级水平,杜鹃属和白珠属为单系,越橘属和水晶兰属不为单系。杜鹃属内部,羊踯躅亚属和常绿杜鹃亚属为姐妹群,二者与杜鹃亚属形成中等支持率的一支,马银花亚属和映山红亚属为姐妹群。(4)杜鹃属19个物种中序列长度≥200 bp的共有单拷贝基因数目为36个,基因的变异率范围为0.81%~11.73%;越橘属12个物种的共有单拷贝基因数目为32个,变异率范围为0~9.09%。

To clarify the structure of plastid genomes of Ericaceae,and to resolve the phylogenetic relationships within Ericaceae,here we analyzed the genome structural characteristics including genome size,number of repeats of 51 species representing 13 genera of Ericaceae,and we adopted maximum likelihood(ML)and Bayesian inference(BI)approaches to resolve their phylogenetic relationships.Plastid genomes were downloaded from the GenBank.Our results suggested that:(1)plastid genomes of mycoheterotrophic and autotrophic species ranged between 26 and 40 kb,150 and 230 kb,separately,difference was significant at the 0.001 level;plastid genomes of non-Rhododendron and Rhododendron species ranged between 150 and 195 kb,152 and 230 kb,separately,difference was significant at the 0.001 level.(2)A comparison of both mycoheterotrophs versus autotrophic,non-Rhododendron and Rhododendron species indicated significant different for repeat content including SSRs(simple sequence repeats),tandem repeats,and dispersed repeats.(3)The inferred phylogenetic tree was well resolved.Eighty-seven percent of all nodes had a bootstrap value≥95%,Ericaceae was monophyletic.Arbutoideae was sister to Monotropoideae,and these were together sister to Pyroloideae,as the earliest diverging lineage.All subfamilies except Arbutoideae(one species included)were recovered as monophyletic.Two genera(Rhododendron and Gaultheria)that were represented by more than one species were monophyletic.Vaccinium and Monotropa were not retrieved as monophyletic.Within Rhododendron,sub-genera relationships suggested Hymenanthes and Pentanthera formed a clade sister to Rhododendron with moderate support.Tsutsusi was sister to Azaleastrum.(4)Of the 19 represented species in Rhododendron,36 shared single copy genes were identified,with the variation percentage ranged from 0.81%to 11.73%.In Vaccinium,the proportion of variability of 32 shared single copy genes ranged from 0 to 9.09%among the 12 species.