Aegilops tauschii Coss. chloroplast genome phylogeny

Abstract

The chloroplast genome phylogeny of Aegilops tauschii was studied. The sequences of four regions of non-coding chloroplast DNA (cpDNA), about 3000 b.p. in total, in 111 Ae. tauschii accessions, 55 of subspecies tauschii (TauL1) and 56 of subspecies strangulata (2 of TauL3 and 54 of TauL2 gene-pool), were used for neighboring joint and maximum likelihood analysis. This revealed that the patterns of cpDNA divergence essentially differ from those of nuclear genome in Ae. tauschii, coinciding only at TauL3, indicating that the chloroplast genome of TauL3 Ae. tauschii differentiated from those of other Ae. tauschii in ancient times. Among the other Ae. tauschii, Taul1 plants have relatively “older” variants of chloroplast genome; moreover, from 55 TauL1 accessions studied, the four accessions originating from the edges of the species area retained the relict variant of cpDNA, with no indels or base pair substitution having taken place in about 3000 b.p. studied, since the differentiation of TauL1 and TauL2 started. Most of TauL1 plants form a cluster with rather similar cpDNA, which also included eight of 54 Taul2 accessions studied, all originating from Caucasia and pre-Caspian Iran. The other 46 TauL2 accessions form a single cluster residing on the tree among the major and several minor, relict, lineages of TauL1. This cluster presents relatively “young”, considerably changed by mutations, and also highly variable cpDNA. It further falls in the two sub-clusters: one presents TauL2 Ae. tauschii from South Caucasia and pre-Caspian Iran, and another—with TauL2 from Caucasia, Continental Iran and Turkmenistan.