甘蓝型油菜扩展蛋白家族的全基因组鉴定及其对缺硼胁迫响应的差异分析

Genome-wide identification of the expansin gene family and differences in transcriptional responses to boron deficiency in Brassica napus L.

以甘蓝型油菜(Brassica napus L.)硼高效品种‘青油10号’和硼低效品种‘Westar 10’为研究对象,采用生物信息学分析、转录组测序和实时荧光定量PCR技术,鉴定其基因组中扩展蛋白的家族成员,并对该基因家族响应缺硼胁迫的表达差异进行分析。结果显示,甘蓝型油菜基因组中包含109个扩展蛋白,可分为4个亚家族,包括:79个扩展蛋白A(BnaEXPAs)、21个扩展蛋白B(BnaEXPBs)、5个类扩展蛋白A(BnaEXLAs)和4个类扩展蛋白B(BnaEXLBs)。同一亚家族中的扩展蛋白具有相对保守的基因结构和蛋白质基序组成。这些扩展蛋白基因分布在19条染色体上,其中10个位于硼高效QTL区间内。转录组测序分析结果表明,缺硼胁迫时‘青油10号’的根、幼叶和老叶中分别有40、18和30个扩展蛋白基因显著上调或下调表达;而‘Westar10’中分别有27、24和41个扩展蛋白基因显著上调或下调表达。其中‘青油10号’根中的BnaC04.EXPA6a,幼叶中的BnaA09.EXPA5以及老叶中的BnaA09.EXPA16、BnaC04.EXPA3、BnaCnn.EXPA5b和BnaA03.EXPA8基因的表达水平均显著高于‘Westar10’。研究结果说明甘蓝型油菜基因组中扩展蛋白基因家族数量庞大,其中高、低效品种间和不同硼水平中差异表达的扩展蛋白可能在甘蓝型油菜低硼适应性中发挥重要作用。

Boron(B)is an essential micronutrient for higher plant growth and development.The most prominent symptoms of B deficiency are associated with primary cell walls.Oilseed rape(Brassica napus L.)is a major oil crop worldwide and shows sensitivity to B deficiency.Expansins mediate plant growth by catalyzing the loosening of cell walls without lysing wall polymers,allowing plants to maintain growth and resist different environmental stresses.However,comprehensive studies on expansins in B.napus and their expression in response to B deficiency are lacking.In the present research,109 B.napus expansins were identified,which could be classified into four subfamilies,including 79 BnaEXPAs,21 BnaEXPBs,five BnaEXLAs,and four BnaEXLBs.Most BnaEXPs clustered in the same subfamily shared relatively conserved exon-intron organization and motif composition.The 109 expansin genes were distributed on 19 chromosomes,and 10 were located in the intervals of B-efficient quantitative trait loci(QTLs).RNA-Seq results showed that,under low B,40,18,and 30 BnaEXPs were significantly up-or down-regulated in the roots,juvenile leaves,and old leaves of B-efficient cultivar‘QY10’,respectively;in contrast,27,24,and 41 BnaEXPs were significantly up-or down-regulated in the roots,juvenile leaves,and old leaves of B-inefficient cultivar‘W10’,respectively.Among them,the expression levels of BnaC04.EXPA6a in roots,BnaA09.EXPA5 in juvenile leaves,and BnaA09.EXPA16,BnaC04.EXPA3,BnaCnn.EXPA5b,and BnaA03.EXPA8 in old leaves of‘QY10’were significantly higher than that of‘W10’.This preliminary analysis of expansin genes provides basic data to help reveal the B-efficiency mechanism in B.napus.