State Key Laboratory for Tree Genetics and Breeding, Nanjing Forestry University, Nanjing, 210037, China.
Commun Biol. 2024 Oct 22;7(1):1367. doi: 10.1038/s42003-024-07091-8.
Gene duplication and divergence are essential to plant evolution. The Arabidopsis type-A response regulator (ARR) family, negative regulators in cytokinin signaling, exemplifies gene expansion and differential retention. Despite extensive research, the understanding of type-A RR homologs in woody plants remains limited. In this study, the evolution history of type-A RR gene families across four rosids and one monocot has been comprehensively investigated. Focusing on Populus deltoides, a unique pair of dispersed duplicates, PdRR8 and PdFERR, is identified, and their duplication is estimated to have occurred in the common ancestor of the four rosids. The duplication remnants corresponding to PdRR8 have been retained in all rosids but the counterpart of PdFERR has been lost. In poplar, PdRR8 shows the highest expression levels in leaves, while PdFERR is specifically expressed in female floral buds. Among various external stimuli, cold strongly represses PdRR8 promoter activity, whereas 6-BA markedly inhibits that of PdFERR. Overexpression of PdRR8 in the Arabidopsis arr16arr17 double-mutant fully complements the reduced hydrotropic response. In contrast, PdFERR fails to rescue the hydrotropic defects of the mutant. Results of evolutionary, expression and functional analyses indicate that PdRR8, rather than PdFERR, is the true ortholog of the ARR16-ARR17 paralogs. Though PdRR8 and PdFERR originate from a common ancestral gene and evolve under strong negative selection, these two dispersed duplicates have exhibited differential expression and some degree of functional divergence.
基因复制和分化是植物进化的关键。拟南芥 A 型反应调节因子（ARR）家族是细胞分裂素信号的负调控因子，是基因扩增和差异保留的典型代表。尽管进行了广泛的研究，但对木本植物 A 型 RR 同源物的理解仍然有限。在这项研究中，全面研究了四个蔷薇科和一个单子叶植物的 A 型 RR 基因家族的进化历史。以泡桐为例，鉴定出一对独特的分散重复基因 PdRR8 和 PdFERR，它们的复制发生在四个蔷薇科的共同祖先中。与 PdRR8 对应的复制残基在所有蔷薇科中都有保留，但 PdFERR 的对应物已经丢失。在杨树中，PdRR8 在叶片中表达水平最高，而 PdFERR 则特异性地在雌性花芽中表达。在各种外部刺激中，低温强烈抑制 PdRR8 启动子的活性，而 6-BA 则显著抑制 PdFERR 的活性。在 arr16arr17 双突变体拟南芥中过表达 PdRR8 可完全补偿降低的向水性反应。相比之下，PdFERR 不能挽救突变体的向水性缺陷。进化、表达和功能分析的结果表明，PdRR8 而不是 PdFERR，是 ARR16-ARR17 旁系同源物的真正同源物。尽管 PdRR8 和 PdFERR 起源于一个共同的祖先基因，并受到强烈的负选择作用，但这两个分散的重复基因表现出差异表达和一定程度的功能分化。
