Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, Yangzhou University, Yangzhou 225009, China.
BMC Evol Biol. 2014 Jun 30;14:147. doi: 10.1186/1471-2148-14-147.
Heat stress transcription factors (Hsfs) regulate gene expression in response to heat and many other environmental stresses in plants. Understanding the adaptive evolution of Hsf genes in the grass family will provide potentially useful information for the genetic improvement of modern crops to handle increasing global temperatures.
In this work, we performed a genome-wide survey of Hsf genes in 5 grass species, including rice, maize, sorghum, Setaria, and Brachypodium, by describing their phylogenetic relationships, adaptive evolution, and expression patterns under abiotic stresses. The Hsf genes in grasses were divided into 24 orthologous gene clusters (OGCs) based on phylogeneitc relationship and synteny, suggesting that 24 Hsf genes were present in the ancestral grass genome. However, 9 duplication and 4 gene-loss events were identified in the tested genomes. A maximum-likelihood analysis revealed the effects of positive selection in the evolution of 11 OGCs and suggested that OGCs with duplicated or lost genes were more readily influenced by positive selection than other OGCs. Further investigation revealed that positive selection acted on only one of the duplicated genes in 8 of 9 paralogous pairs, suggesting that neofunctionalization contributed to the evolution of these duplicated pairs. We also investigated the expression patterns of rice and maize Hsf genes under heat, salt, drought, and cold stresses. The results revealed divergent expression patterns between the duplicated genes.
This study demonstrates that neofunctionalization by changes in expression pattern and function following gene duplication has been an important factor in the maintenance and divergence of grass Hsf genes.
热应激转录因子（Hsfs）调节植物对热和许多其他环境胁迫的基因表达。了解禾本科植物 Hsf 基因的适应性进化将为现代作物的遗传改良提供有价值的信息，以应对全球气温的升高。
本研究通过描述它们的系统发育关系、在非生物胁迫下的适应性进化和表达模式，对 5 种禾本科植物（包括水稻、玉米、高粱、柳枝稷和短柄草）中的 Hsf 基因进行了全基因组调查。禾本科植物的 Hsf 基因根据系统发育关系和同线性分为 24 个直系同源基因簇（OGC），表明在祖先禾本科植物基因组中存在 24 个 Hsf 基因。然而，在测试的基因组中鉴定到 9 个复制和 4 个基因丢失事件。最大似然分析揭示了 11 个 OGC 进化过程中的正选择效应，并表明具有复制或丢失基因的 OGC 比其他 OGC 更容易受到正选择的影响。进一步的研究表明，在 9 个同源基因对中的 8 个中，只有一个复制基因受到正选择的影响，这表明新功能化有助于这些复制基因对的进化。我们还研究了水稻和玉米 Hsf 基因在热、盐、干旱和冷胁迫下的表达模式。结果表明，复制基因之间存在不同的表达模式。
本研究表明，表达模式和功能的改变导致的新功能化是禾本科 Hsf 基因维持和分化的一个重要因素。
