特早花甘蓝型油菜的开花特征及特早花候选基因鉴定

Identification of the Flowering Characteristics and Candidate Genes for a Very-early-flowering Oilseed Rape

开花是植物从营养生长进入生殖生长的重要阶段。油菜早花早熟,可有效解决油菜与其他夏季作物的茬口矛盾。挖掘不同的早花油菜资源,研究油菜早花性状形成的分子机理,可促进利用分子技术快速选育早熟油菜的育种进程。本研究以1个新发现的稳定遗传的特早花油菜迎春一号为研究对象,在覆盖全年9个月的时间中设计了15个不同的播种期,调查其开花特性。结果显示,迎春一号在不同季节播种均可顺利开花,其对低温春化的温度需求更弱于普通春性油菜。将迎春一号与半冬性早花品系FM4和半冬性晚花品系FM5进行比较发现,在10月播种于半冬性生态区种植环境下,迎春一号既能快速进入花期,又表现较好的耐寒性,综合农艺性状表现较好。对迎春一号开展分子生物学试验发现,在高温生长环境下,位于油菜A02、A03、C02和C03染色体上的春化途径关键基因BnaFLC的6个同源拷贝在迎春一号的营养生长阶段均出现了多拷贝基因的同步下调。以半冬性早花品系FM4和半冬性晚花品系FM5为对照,利用50×全基因组重测序技术检测得到与油菜全基因组1064个开花基因相关的16229个SNPs和5842个InDels。其中,迎春一号特异的且会导致开花基因编码蛋白变异的SNPs和InDels分别为69个和34个,包含与BnaFLC基因具有正向调控关系的14个SNPs和4个InDels,最终获得11个潜在候选基因。除了1个BnaFLC基因本身以外,其余基因均处于BnaFLC上游区域,且对BnaFLC基因的表达起正向调控作用。

Flowering is a crucial step for the transition from vegetative to reproductive growth in plant′s life cycle.The character of early-flowering and early-maturing of oilseed rape is the key to solve the conflict between oilseed rape and other summer crops in the multiple-cropping system.Identification of early-flowering oilseed rape and dissecting the basis of early-flowering are conducive to accelerating the procedures of molecular breeding of early-maturing varieties.A novel and stably inherited very-early-flowering oilseed rape Yingchun Yi Hao was evaluated for flowering characteristics in the present study,with 15 sowing stages distributed in nine different months.The results showed that Yingchun Yi Hao sown in the different dates successfully flowered,and unlike common spring type oilseed rapes,was not demanding of low temperature for vernalization.Compared with early-flowering semi-winter line FM4 and late-flowering semi-winter line FM5,Yingchun Yi Hao sown in semi-winter ecological environments in October more rapidly entered the flowering stage,and also was superior in cold tolerance and in general agronomic traits.The molecular experiment revealed that six copies of vernalization key gene Bna FLC on chromosomes A02,A03,C02 and C03 synchronously down-regulated the expression in Yingchun Yi Hao grown in high temperature environment during the vegetative growth stage.50×whole genome sequencing was performed for Yingchun Yi Hao and two reference samples,line FM4 and FM5,which identified 16229 SNPs and 5842 In Dels correlated to 1064 flowering time genes in Brassica napus,and screened out 69 SNPs and 34 In Dels that caused the variation of flowering time genes encoding proteins specific to Yingchun Yi Hao,including 14 SNPs and 4 In Dels that showed positive regulation with Bna FLC,and 11 genes were deduced to be candidate genes for very-early-flowering of Yingchun Yi Hao.These genes,except Bna FLC itself,are located upstream of Bna FLC and positively regulate the expression of Bna FLC.