茶树叶绿体基因组：三倍体中国种、二倍体中国种和二倍体阿萨姆种 / 四六文摘

Comparative chloroplast genomes: insights into the evolution of the chloroplast genome of Camellia sinensis and the phylogeny of Camellia

第一作者

Li Li

第一单位

武夷学院

通讯作者

Yongcong Hong

Abstract

背景+问题：It has long been suggested that C. sinensis var. sinensis and C. sinensis var. assamica may have distinct origins, but the idea that C. sinensis var. assamica consists of two distinct lineages (Chinese Assamica type and Indian Assamica type) that were domesticated separately is more controversial.

cp genome can provide a wealth of evolutionary information. So far, the cp genome of the polyploid tea plant has not been reported, and the possible effects of polyploidization on the cp genome of tea plant need to be further explored.

主要研究：Here, we determined the chloroplast genome of the first natural triploid Chinary type tea (‘Wuyi narcissus’ cultivar of Camellia sinensis var. sinensis, CWN) and conducted the genome comparison with the diploid Chinary type tea (CSS) and two types of diploid Assamica type teas (Camellia sinensis var. assamica: Chinese Assamica type tea, CSA and Indian Assamica type tea, CIA). Further, the evolutionary mechanism of the chloroplast genome of Camellia sinensis and the relationships of Camellia species based on chloroplast genome were discussed.

结果1：Chinese tea and Indian tea had significant differences in the structural characteristic and the codon usage of the chloroplast genome. None of 292 different Camellia sinensis cultivars had similar sequence characteristic to triploid CWN, but the other four Camellia species did.

结果2：Estimations of the divergence time showed that CIA diverged from the common ancestor of two Assamica type teas about 6.2 Mya (CI: 4.4–8.1 Mya). CSS and CSA diverged to each other about 0.8 Mya (CI: 0.4–1.5 Mya).

结果3：Phylogenetic clustering was not exactly consistent with the current taxonomy of Camellia

结论：Chinese tea and Indian tea might have undergone different selection pressures. Chloroplast transfer occurred during the polyploid evolution in Camellia sinensis. In addition, our results supported the three different domestication origins of Chinary type tea, Chinese Assamica type tea and Indian Assamica type tea. And, the current classification of some Camellia species might need to be further discussed.