棉花SMXL基因家族的全基因组分析及表达分析

Genome-wide identification and expression analysis of the SMXL gene family in cotton

独脚金内酯(strigolactones,SLs)是一种新型植物激素,在植物生长发育中发挥重要作用.目前在棉花中对SL研究仍较少,探究SL影响棉花生长发育及纤维品质形成的功能和机制具有重要意义.SMXL(SUPPRESSOR OF MAX21-like)是独角金内酯信号通路的关键基因,充当SL信号转导的阻遏物,关于棉花SMXL基因的研究尚未见报道.本文以陆地棉、海岛棉、亚洲棉及雷蒙德氏棉全基因组为基础,运用生物信息学方法,根据SMXL蛋白序列结构域特征鉴定到16个GhSMXL基因、16个GbSMXL基因、8个GaSMXL基因和8个GrSMXL基因.系统发育分析发现SMXL分为4个亚家族:SMXL-Ⅰ(SMXL1,2),SMXL-Ⅱ(SMXL6,7,8),SMXL-Ⅲ(SMXL3)和SMXL-Ⅳ(SMXL4,5).对SMXL的进化特征分析发现,位于同一亚组间的SMXL成员具有相似的基因结构与蛋白结构.分析发现,片段复制是SMXL成员在棉花中扩张的主要方式.组织表达谱分析显示,在陆地棉中GhSMXL1-A,GhSMXL1-D,GhSMXL7-1-A,GhSMXL7-1-D,GhSMXL8-1-A,GhSMXL8-1-D在根、茎、叶、纤维及胚珠中优势表达;在亚洲棉中GaSMXL8-1,GaSMXL1,GaSMXL7在根、茎、叶和胚珠中优势表达.这些优势表达基因多数位于SMXL-Ⅰ,SMXL-Ⅱ亚家族,推测位于SMXL-Ⅰ,SMXL-Ⅱ亚家族中的多数基因可能是陆地棉或亚洲棉中在根、茎、叶和胚珠发育中发挥功能的关键基因.胁迫表达谱分析显示:SMXL-Ⅱ和SMXL-Ⅲ亚家族的基因(GhSMXL8-1-A,GhSMXL8-1-D,GhSMXL8-2-A,GhSMXL8-2-D,GhSMXL3-1-A,GhSMXL3-1-D,GhSMXL3-2-A,GhSMXL3-3-A和GhSMXL3-3-D)在盐、旱、低温、高温不同的胁迫模式下具有不同的响应方式,同一基因可能同时响应两种不同胁迫方式,例如GhSMXL8-1-A响应低温胁迫同时也响应盐胁迫,推测这些基因可能调控陆地棉非生物胁迫的响应.本研究为此后深入研究棉花SMXL基因功能奠定了基础.

Strigolactones(SLs)is a novel plant hormone,which plays an important role in plant growth and development.At present,there are still few studies on SL in cotton.Therefore,it is necessary to explore the function and mechanism of SL on cotton growth and fiber quality.SMXLs(SUPPRESSOR OF MAX21-likes)are key genes of the SL pathway and act as repressors of SL signal transduction.Until now,there are no studies about SMXLs gene in cotton.In this study,16 GhSMXLs,16 GbSMXLs,8 GaSMXLs,and 8 Gr SMXLs were identified in G.raimondii,G.arboreum,G.hirsutum,and G.barbadense.Phylogenetic analysis revealed that SMXLs were divided into four subfamilies:SMXL-Ⅰ(SMXL1,2),SMXL-Ⅱ(SMXL6,7,8),SMXL-Ⅲ(SMXL3),and SMXL-ⅠV(SMXL4,5).The evolutionary characteristics showed that SMXL members located in the same subgroup had similar gene and protein structures.Fragment replication was the main reason for SMXL member expansion in cotton.Tissue expression profile analysis showed that GhSMXL1-A,GhSMXL1-D,GhSMXL7-1-A,GhSMXL7-1-D,GhSMXL8-1-A,and GhSMXL8-1-D were dominant expressions in roots,stems,leaves,fibers and ovules.GaSMXL8-1,GaSMXL1,and GaSMXL7 were mainly expressed in roots,stems,leaves and ovules.Interestingly,most of the dominant genes were located in the SMXL-Ⅰand SMXL-Ⅱsubfamilies,indicating that these genes might be the key genes in root,stem,leaf and ovule development.Stress expression profile analysis showed that the SMXL-Ⅱand SMXL-Ⅲsubfamily genes(GhSMXL8-1-A,GhSMXL8-1-D,GhSMXL8-2-A,GhSMXL8-2-D,GhSMXL3-1-A,GhSMXL3-1-D,GhSMXL3-2-A,GhSMXL3-3-A,and GhSMXL3-3-D)have different expression patterns under different salt,drought,low temperature and high temperature treatment.Furthermore,some genes respond to different stress treatment,for example,GhSMXL8-1-A responds to both low temperature stress and salt stress,implying that these genes may regulate the response of abiotic stress in cotton.This study lays the foundation for further study of cotton SMXLs gene function.