Agronomy Department, University of Florida, Gainesville, FL, USA.
State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China.
J Exp Bot. 2021 Feb 24;72(4):1104-1118. doi: 10.1093/jxb/eraa505.
Microbial symbiosis in legumes is achieved through nitrogen-fixing root nodules, and these are important for sustainable agriculture. The molecular mechanisms underlying development of root nodules in polyploid legume crops are largely understudied. Through map-based cloning and QTL-seq approaches, we identified a pair of homoeologous GRAS transcription factor genes, Nodulation Signaling Pathway 2 (AhNSP2-B07 or Nb) and AhNSP2-A08 (Na), controlling nodulation in cultivated peanut (Arachis hypogaea L.), an allotetraploid legume crop, which exhibited non-Mendelian and Mendelian inheritance, respectively. The segregation of nodulation in the progeny of Nananbnb genotypes followed a 3:1 Mendelian ratio, in contrast to the 5:3~1:1 non-Mendelian ratio for nanaNbnb genotypes. Additionally, a much higher frequency of the nb allele (13%) than the na allele (4%) exists in the peanut germplasm collection, suggesting that Nb is less essential than Na in nodule organogenesis. Our findings reveal the genetic basis of naturally occurred non-nodulating peanut plants, which can be potentially used for nitrogen fixation improvement in peanut. Furthermore, the results have implications for and provide insights into the evolution of homoeologous genes in allopolyploid species.
豆科植物中的微生物共生是通过固氮根瘤实现的，这对于可持续农业非常重要。多倍体豆科作物根瘤发育的分子机制在很大程度上尚未得到研究。通过基于图谱的克隆和 QTL-seq 方法，我们鉴定了一对同源 GRAS 转录因子基因，Nodulation Signaling Pathway 2（AhNSP2-B07 或 Nb）和 AhNSP2-A08（Na），它们控制栽培花生（Arachis hypogaea L.）的结瘤，这是一种异源四倍体豆科作物，分别表现为非孟德尔遗传和孟德尔遗传。在 Nananbnb 基因型后代中的结瘤分离遵循孟德尔 3:1 的比例，而 nanaNbnb 基因型的分离则是非孟德尔的 5:3~1:1 比例。此外，在花生种质资源中，nb 等位基因（13%）的存在频率远高于 na 等位基因（4%），这表明 Nb 在根瘤器官发生中的作用不如 Na 重要。我们的研究结果揭示了自然发生的不结瘤花生植物的遗传基础，这可能为提高花生的固氮能力提供了潜在的应用价值。此外，这些结果对同源基因在异源多倍体物种中的进化具有启示意义。
