中文摘要：

β-淀粉酶（beta-amylase,BAM）是一类关键的淀粉水解酶,在禾谷类作物生长发育过程中起着重要作用,与植物多种非生物胁迫响应相关。本研究通过系统发育分析,将水稻、玉米、高粱、谷子、二穗短柄草5种禾本科植物中共54个BAM基因分为10个同源基因簇,每个同源基因簇都涵盖了这5个物种,因此推测在禾本科祖先物种中至少含有10个BAM基因,并且在禾本科植物分化后没有发生明显的基因丢失事件。基于对编码蛋白质序列的功能分化分析,表明同源基因簇间存在明显的进化速率的差异。对10个同源基因簇进行了适应性进化检测,发现有3个同源簇在禾本科植物的进化过程中经历了适应性进化。此外,对水稻β-淀粉酶的表达分析发现,一些β-淀粉酶具有组织特异性表达特征,并且至少有5个水稻的β-淀粉酶基因具有受到非生物逆境的胁迫而表现出不同的表达模式。本研究结果为进一步探讨禾本科BAM基因的生物学功能提供了一定的理论基础。

英文摘要：

Beta- amylase（BAM） plays a central role in the complete degradation of starch tometabolisable or fermentable sugars during the germination or maltingof cereal grains. It was found to be involved in the abiotic stress responsesof crops. A genome- wide survey of BAM genes in 5 grass species was performed, including rice, maize, sorghum, Setaria, and Brachypodium, by describing their phylogenetic relationships, functional divergence, and adaptive evolution. The phylogeny classified the gramineous BAM genes into 10 clusters of orthologous genes（COGs）, and the genes in the same COG shared the syntenic region. Functional divergence analysis provided statistical evidence that both the shift in the evolutionary rate pattern and cluster- specific alterations of amino acid physiochemical properties contributed to COG- specific functional evolution of BAM genes in grasses. In addition, 3 COGs were found to be influenced by positive selection through maximum likelihood analysis. The expression patterns of rice BAM genes were investigated, and the resultsrevealed that they were differentially expressed under the treatments of abiotic stresses. These observations may provide useful references for further functional detection of BAM genes in grasses.