Zhao Man, Gu Yongzhe, He Lingli, Chen Qingshan, He Chaoying
State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, 100093, Beijing, China.
University of Chinese Academy of Sciences, Yuquan Road 19, 100049, Beijing, China.
BMC Plant Biol. 2015 May 15;15:120. doi: 10.1186/s12870-015-0519-0.
The DA1 gene family is plant-specific and Arabidopsis DA1 regulates seed and organ size, but the functions in soybeans are unknown. The cultivated soybean (Glycine max) is believed to be domesticated from the annual wild soybeans (Glycine soja). To evaluate whether DA1-like genes were involved in the evolution of soybeans, we compared variation at both sequence and expression levels of DA1-like genes from G. max (GmaDA1) and G. soja (GsoDA1).
Sequence identities were extremely high between the orthologous pairs between soybeans, while the paralogous copies in a soybean species showed a relatively high divergence. Moreover, the expression variation of DA1-like paralogous genes in soybean was much greater than the orthologous gene pairs between the wild and cultivated soybeans during development and challenging abiotic stresses such as salinity. We further found that overexpressing GsoDA1 genes did not affect seed size. Nevertheless, overexpressing them reduced transgenic Arabidopsis seed germination sensitivity to salt stress. Moreover, most of these genes could improve salt tolerance of the transgenic Arabidopsis plants, corroborated by a detection of expression variation of several key genes in the salt-tolerance pathways.
Our work suggested that expression diversification of DA1-like genes is functionally associated with adaptive radiation of soybeans, reinforcing that the plant-specific DA1 gene family might have contributed to the successful adaption to complex environments and radiation of the plants.
DA1基因家族是植物特有的，拟南芥中的DA1基因调控种子和器官大小，但在大豆中的功能尚不清楚。栽培大豆（Glycine max）被认为是由一年生野生大豆（Glycine soja）驯化而来。为了评估类DA1基因是否参与了大豆的进化，我们比较了栽培大豆（GmaDA1）和野生大豆（GsoDA1）中类DA1基因在序列和表达水平上的差异。
大豆直系同源基因对之间的序列一致性极高，而大豆物种中的旁系同源拷贝则表现出相对较高的差异。此外，在发育过程以及诸如盐胁迫等非生物胁迫条件下，大豆中类DA1旁系同源基因的表达变异远大于野生大豆和栽培大豆之间的直系同源基因对。我们进一步发现，过表达GsoDA1基因不会影响种子大小。然而，过表达这些基因会降低转基因拟南芥种子对盐胁迫的萌发敏感性。此外，这些基因中的大多数能够提高转基因拟南芥植株的耐盐性，这一点在耐盐途径中几个关键基因的表达变异检测中得到了证实。
我们的研究表明，类DA1基因的表达多样化在功能上与大豆的适应性辐射相关，这进一步证明了植物特有的DA1基因家族可能有助于植物成功适应复杂环境并实现辐射进化。
