雷蒙德氏棉扩展蛋白基因家族的鉴定和特征分析

扩展蛋白具有松驰细胞壁和增加细胞壁柔韧性的功能。为了弄清该基因家族在雷蒙德氏棉中的特征,利用隐马尔科夫模型(HMM)在雷蒙德氏棉基因组中进行扩展蛋白家族基因成员的鉴定,获得了39个扩展蛋白基因家族成员,分布在12条染色体上。系统发育分析将其归入EXPA、EXPB、EXLA和EXLB共4个亚家族,分别含有26,4,3,6个基因。各亚家族中扩展蛋白基因具有相对多样化的基因结构;扩展蛋白基因家族在进化中经历了3次扩张;染色体片段重复是该基因家族扩张的主要方式;扩张后纯化选择占主导地位。比较棉纤维发育不同时期及叶片、花瓣的深度测序和基因芯片表达谱,发现大部分扩展蛋白基因参与了雷蒙德氏棉纤维、叶片和花瓣的生长发育,在不同的时空范围均表现出表达多样性。Gr EXLA1、Gr EXLA2和Gr EXPA16在花瓣中优势表达,Gr EXPA23和Gr EXPA24在叶片中表达水平较高,推测这些基因的表达分别参与了花瓣和叶片的发育进程;其余的基因,在纤维的不同发育阶段,表现出不同的表达丰度。研究结果有助于了解棉属扩展蛋白基因家族的特征及功能,为深入剖析棉纤维发育过程中的分子调控机理提供了基础。

Genome-wide Identification and Characterization of Expansin Gene Family in Gossypium raimondii

Expansin can loosen the components of rigid plant cell walls and thereby allow cell expansion.To get insight into expansin genes in Gossypium raimondii,genome-wide exploration and comprehensive characterization of the G.raimondii expansin gene family members were conducted,and 39 expansin genes(including 26 EXPA,4 EXPB,3 EXLA and 6 EXLB,which was classified based on the phylogenetic tree) were identified.The results revealed that expansin family genes were located on 12 of 13 G.raimondii chromosomes.And the gene structures were relatively diverse(not conserved) in each subgroup.Evolutionary analysis of expansins revealed that chromosome segmental duplications contributed mainly to the three evolutionary expansions of expansin family,which had experienced negative selection pressure.The expression pattern of expansin genes under series of fiber development stages,in leaf and petal indicated that most expansin genes (showing diverse and specific expression pattern) might participate in fiber development processes including fiber initiation and elongation,and in morphogenesis of leaf and petal.This identification and characterization provided the complete profiles of Gossypium expansin family genes for future study on their functions related to the molecular mechanisms of fiber and other tissues development.