Data_Sheet_1_Identification of a Locus Controlling Compound Raceme Inflorescence in Mungbean [Vigna radiata (L.) R. Wilczek].docx

Mungbean [Vigna radiata (L.) R. Wilczek] produces a compound raceme inflorescence that branches into secondary inflorescences, which produce flowers. This architecture results in the less-domesticated traits of asynchronous pod maturity and multiple harvest times. This study identified the genetic factors responsible for the compound raceme of mungbean, providing a unique biological opportunity to improve simultaneous flowering. Using a recombinant inbred line (RIL) population derived from VC1973A, an elite cultivar with a compound raceme type, and IT208075, a natural mutant with a simple raceme type, a single locus that determined the inflorescence type was identified based on 1:1 segregation ratio in the F8 generation, and designated Comraceme. Linkage map analysis showed Comraceme was located on chromosome 4 within a marker interval spanning 520 kb and containing 64 genes. RILs carrying heterozygous fragments around Comraceme produced compound racemes, indicating this form was dominant to the simple raceme type. Quantitative trait loci related to plant architecture and inflorescence have been identified in genomic regions of soybean syntenic to Comraceme. In IT208075, 15 genes were present as distinct variants not observed in other landrace varieties or wild mungbean. These genes included Vradi04g00002481, a development-related gene encoding a B3 transcriptional factor. The upstream region of Vradi04g00002481 differed between lines producing the simple and compound types of raceme. Expression of Vradi04g00002481 was significantly lower at the early vegetative stage and higher at the early reproductive stage, in IT208075 than in VC1973A. Vradi04g00002481 was therefore likely to determine inflorescence type in mungbean. Although further study is required to determine the functional mechanism, this finding provides valuable genetic information for understanding the architecture of the compound raceme in mungbean.

绿豆[Vigna radiata (L.) R. Wilczek]具有复总状花序结构，其花序会分化出二级花序，进而产生花朵。该花序结构导致了驯化程度较低的性状：荚果成熟不同步以及需多次采收。本研究明确了调控绿豆复总状花序形成的遗传因子，为改良绿豆的同步开花特性提供了独特的生物学研究契机。本研究以复总状花序型优良栽培品种VC1973A与单总状花序型自然突变体IT208075构建的重组自交系（recombinant inbred line, RIL）群体为材料，基于F8代群体中1:1的分离比，鉴定到1个调控花序类型的单基因座，并将其命名为Comraceme。连锁图谱分析显示，Comraceme定位于第4号染色体上一个跨度为520 kb的标记区间内，该区间包含64个基因。携带Comraceme位点周围杂合片段的重组自交系均表现出复总状花序，说明该花序类型对单总状花序呈显性。在与Comraceme位点同线的大豆基因组区域中，已鉴定出与株型及花序发育相关的数量性状基因座（quantitative trait loci, QTL）。在突变体IT208075中，存在15个在其他地方品种或野生绿豆中未检测到的特异变异基因。这些基因包括Vradi04g00002481，它是一个编码B3转录因子的发育相关基因。Vradi04g00002481的上游调控区域在单总状花序型与复总状花序型材料中存在差异。与VC1973A相比，IT208075中Vradi04g00002481在营养生长早期的表达量显著更低，而在生殖生长早期的表达量显著更高。因此，Vradi04g00002481极有可能是调控绿豆花序类型的关键基因。尽管仍需开展进一步研究以阐明其功能机制，但该研究结果为解析绿豆复总状花序的分子调控机制提供了极具价值的遗传信息。