Soybean (Glycine max) is a plant sensitive to photoperiod,which determines its maturity date and therefore its adaptation to respective eco-regions.The soybean varieties from temperate regions flower and mature very early in tropical regions (short photoperiod),which leads to low yields and limits the commercial cultivation of soybean in these regions.The discovery of long-juvenile (L J) soybean varieties is a major breakthrough to overcome this problem.Under short photoperiod,the LJ soybean varieties show delayed flowering and maturity time,enhanced growth and therefore,higher yields than temperate varieties.Previous studies found that locus J had a major contribution to the LJ trait.Recently,Chinese scientists cloned the J gene by fine-mapping and found it as an ortholog of Arabidopsis thaliana EARLY FLOWERING 3 (ELF3).The functions of J gene were confirmed by transgenic complementation and near-isogenic lines:thejgenotype showed later flowering and maturity date and more yield potential than the J genotype.Further studies showed that the J protein bound to the promoter of the E1 gene (a legume-specific flowering repressor) to downregulate E1 expression,thereby relieving the suppression of E1 on soybean FLOWERING LOCUS T (FT) genes,which leads to early flowering under short photoperiod.In addition,multiplej alleles and haplotypes were identified from soybean germplasm.The study leads to a new direction in genetic research of growth periods for the expansion of soybean to tropical regions.%大豆(Glycine max)是光周期敏感的植物,该特性是决定其生育期及其生态适应区的关键因素.温带的大豆品种引种到热带地区(短日照)时,开花期和成熟期提前、产量降低,限制了大豆在热带地区的种植.长童期(LJ)大豆品种的发现是解决该问题的重要突破.在短日照条件下,LJ品种比温带品种开花晚、体量大、成熟晚且产量提高.前期研究发现,J位点是控制LJ性状的关键位点.近期,我国科学家通过精细定位克隆了J基因,发现其与拟南芥(Arabidopsis thaliana)早花基因(ELF3)同源.他们通过功能互补和近等基因系等方法验证了J基因的功能,在短日照条件下,等位基因j比J开花晚、成熟晚且产量提高.进一步研究发现,J蛋白与E1基因(豆科植物开花抑制因子)的启动子结合抑制E1基因的表达,从而解除E1对大豆开花基因(FT)的抑制,促进大豆在短日照下开花.研究还发现在大豆种质资源中存在多种j等位变异.该研究引领了大豆生育期遗传研究的新方向,揭示了大豆向热带地区发展的遗传基础.
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