水稻长日照开花因子Lfm1的图位克隆

Map-based Cloning of Rice Flowering Factor Lfm1 Under Long Days

开花期是水稻最重要的农艺性状之一,水稻的花期决定着水稻的地区适应性和最终产量。人工选择使水稻从短日照向长日照、低纬度向高纬度扩张,因此水稻已逐渐进化出适应长日照条件下的开花调控机制。目前,虽然鉴定了一些影响水稻长日照的开花基因如SDG724、RFT1、EHD4、DTH2,但是挖掘水稻长日照开花基因还十分有限。本研究通过筛选水稻突变体库,获得一批在长日照下花期有显著差异的突变体材料,其中一份突变体lfm1(late-flowering mutant1),在长日照条件下开花延迟,在短日照条件下开花时间正常。通过图位克隆,将Lfm1基因初定位至第8染色体端粒附近。进一步的精细定位将Lfm1基因定位于分子标记8-0.269和与8-0.283之间,范围为12 kb,该区域包括3个候选基因。经测序分析发现,在突变体lfm1中,LOC_Os08g01420基因的第六外显子2800处缺失9个碱基,突变体lfm1等位于已报道的突变体ehd3。在适度(中日照条件下,~12 h/12 h)的光照条件下,突变体lfm1表现为穗粒数增多,生育期略延长,具有应用于生产的潜力。Lfm1基因的克隆为培育适应不同生态区域的水稻材料提供了重要的基因资源。

Flowering time is one of the most important agronomic traits and determines the regional adaptability and yield in rice.Artificial selection makes rice expand from short-day to long-day and low-latitude to high-latitude,thus rice has gradually evolved a flowering regulation mechanism adapted to long-day.Currently,the mining of rice long-day flowering genes is still very limited although some flowering genes,such as SDG724,RFT1,EHD4,and DTH2 that affect rice long-day trait,have been identified.In this study,a batch of mutant materials with significant differences in flowering period under long-day were obtained by screening the rice mutant library.One of these mutants,lfm1(late-flowering mutant1),delayed flowering under long-day conditions and was normal under short-day conditions.Through map-based cloning,the Lfm1 gene was initially located near the telomere of chromosome 8.Lfm1 was located near the telomere of chromosome 8.Fine mapping revealed that the Lfm1 gene was located between the molecular markers 8-0.269 and 8-0.283.There were 3 candidated genes in this region of 12 kb.Through sequencing analysis,9 bp deletion at position 2800 of the sixth exon of the LOC_Os08g01420 was found in lfm1,and lfm1 was an allele of ehd3.It is worth of mentioning that under moderate light conditions(~12 h/12 h),the mutant lfm1 showed an increase in the number of grains per panicle and a slightly longer growth period,thus it can be used in production potentially.The cloning of Lfm1 gene provides an important gene resource for breeding rice materials adapted to different ecological regions.