大豆是典型的短日照作物，对光周期的敏感性决定大豆品种的适宜种植区域。在光周期调控的大豆开花途径中，开花抑制因子E1起主导作用。E1La和E1Lb是E1的同源基因，功能与E1类似。本研究利用RNA干扰（RNAi）技术在大豆品种自贡冬豆中同时沉默了E1和E1La/b基因。结果显示，与受体品种自贡冬豆相比，RNAi株系开花期和成熟期大幅度提前，光周期敏感性明显下降。在RNAi超早熟株系中，开花抑制基因GmFT4的表达水平显著下降，而开花促进基因GmFT2a/GmFT5a的表达水平明显上升。生育期组鉴定结果显示，自贡冬豆的生育期组属于MG VIII，为极晚熟品种，而RNAi株系的生育期组为MG 000，属超早熟新种质，可在中国最北部（53.5°N）的漠河市北极村种植。本研究验证了E1和E1La/b对大豆开花期和成熟期的负调控作用，创制出超早熟大豆新材料，为显著钝化大豆品种的光周期敏感性，大幅度缩短生育期，实现南方大豆种质资源在北方大豆主产区的有效利用，拓宽高寒地区大豆的遗传基础提供了新的途径。

As an important food crop and oil crop, soybean (Glycine max [L.] Merr.) is capable of nitrogen-fixing by root nodule.  Previous studies showed that GmNMH7, a transcription factor of MADS-box family, is associated with nodule development, but its specific function remained unknown.  In this study, we found that GmNMH7 was specifically expressed in root and nodule and the expression pattern of GmNMH7 was similar to several genes involved in early development of nodule (GmENOD40-1, GmENOD40-2, GmNFR1a, GmNFR5a, and GmNIN) after rhizobia inoculation.  The earlier expression peak of GmNMH7 compared to the other genes (GmENOD40-1, GmENOD40-2, GmNFR1a, GmNFR5a, and GmNIN) indicated that the gene is related to the nod factor (NF) signaling pathway and functions at the early development of nodule.  Over-expression of GmNMH7 in hairy roots significantly reduced the nodule number and the root length.  In the transgenic hairy roots, over-expression of GmNMH7 significantly down-regulated the expression levels of GmENOD40-1, GmENOD40-2, and GmNFR5α.  Moreover, the expression of GmNMH7 could respond to abscisic acid (ABA) and gibberellin (GA₃) treatment in the root of Zigongdongdou seedlings.  Over-expressing GmNMH7 gene reduced the content of ABA, and increased the content of GA₃ in the positive transgenic hairy roots.  Therefore, we concluded that GmNMH7 might participate in the NF signaling pathway and negatively regulate nodulation probably through regulating the content of GA₃.
 

Soybean (Glycine max (L.) Merr.) is a typical short-day and warm season plant, and the interval between emergence and flowering has long been known to be regulated by environmental factors, primarily photoperiod and temperature. While the effects of photoperiod and temperature on soybean flowering have been extensively studied, a dissection of the component photo-thermal effects has not been documented for Chinese germplasm. Our objective of the current study was to evaluate the independent- and interactive-photo-thermal responses of 71 cultivars from 6 ecotypes spanning the soybean production regions in China. These cultivars were subjected in pot experiments to different temperature regimes by planting in spring (low temperature (LT)) and summer (high temperature (HT)), and integrating with short day (SD, 12 h), natural day (ND, variable day-length), and long day (LD, 16 h) treatments over two years. The duration of the vegetative phase from emergence to first bloom (R1) was recorded, and the photo-thermal response was calculated. The outcome of this characterization led to the following conclusions: (1) There were significant differences in photo-thermal response among the different ecotypes. High-latitude ecotypes were less sensitive to the independent- and interactive-photo-thermal effects than low-latitude ecotypes; and (2) there was an interaction between photoperiod and temperature, with the effect of photoperiod on thermal sensitivity being greater under the LD than the SD condition, and with the effect of temperature on photoperiodic sensitivity being greater under the LT than the HT condition. The strengths and limitations of this study are discussed in terms of implications for current knowledge and future research directions. The study provides better understanding of photo-thermal effects on flowering in soybean genotypes from different ecotypes throughout China and of the implications for their adaptation more broadly.