数百万年前大麦捕获的源自Panicum的染色体片段仍保留了一组与胁迫相关的基因
种内变异是物种进化成功的基石。从遥远的来源获得遗传物质是细菌的一种重要适应机制，但在真核生物中也可以发挥作用。
本文研究了大麦属（Pooideae）种核基因组中圆锥花序（禾本科，圆锥花序科）起源染色体片段的性质和进化。该片段位于一对不含NOR的染色体上，在亚洲大麦和南美大麦中分别跨越440kb和219kb。
这两个物种中片段的保守共线性和微共线性表明了片段的共同起源，这是在各自的大麦谱系5–1.7 mya分裂之前获得的。外源DNA的一个主要部分由几个约68kb长的重复片段组成，其中包含5个应激相关蛋白编码基因和转座因子。
然而在这些重复序列之外，该位点被来自宿主基因组的多个转座因子侵入，重复片段相当完整并且似乎被保存下来。如保守的阅读框、少量的非同义突变和mRNA的表达所示，蛋白质编码基因仍有部分功能。一个针对穗蛋白编码基因的大麦品种的筛选结果显示，在所有的狭茎类植物中都存在这种基因。
总之，我们的研究表明，禾本科基因组可以包含从远缘种获得的大的基因组片段。这些片段通常未被发现，但它们可能在物种的进化和适应中发挥重要作用。
Intra‐specific variability is a cornerstone of evolutionary success of species. Acquiring genetic material from distant sources is an important adaptive mechanism in bacteria, but it can also play a role in eukaryotes. In this paper we investigate the nature and evolution of chromosomal segment of panicoid (Poaceae, Panicoideae) origin occurring in the nuclear genomes of species of the barley genus Hordeum (Pooideae). The segment, spanning over 440 kb in Asian Hordeum bogdanii and 219 kb in South American H. pubiflorum, resides on a pair of NOR‐bearing chromosomes. Conserved synteny and micro‐colinearity of the segment in both species indicate a common origin of the segment, which was acquired before the split of the respective barley lineages 5–1.7 mya. A major part of the foreign DNA consists of several ~68 kb long repeated blocks containing five stress‐related protein‐coding genes and transposable elements. Whereas outside these repeats the locus was invaded by multiple transposable elements from the host genome, the repeated blocks are rather intact and appear to be preserved. The protein‐coding genes remained partly functional, as indicated by conserved reading frames, a low amount of non‐synonymous mutations and expression of mRNA. A screen across Hordeum species targeting the panicoid protein‐coding genes revealed the presence of the genes in all species of section Stenostachys. In summary, our study shows that grass genomes can contain large genomic segments obtained from distantly related species. These segments usually remain undetected, but they may play an important role in the evolution and adaptation of species.
links:
A Panicum‐derived chromosomal segment captured by Hordeum a few million years ago preserves a set of stress‐related genes10.1111/tpj.15167
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