SHORT-ROOT paralogs mediate feedforward regulation of D-type cyclin to promote nodule formation in soybean

Abstract

Significance Nitrogen fixation is economically important in agriculture. Enhancing nodulation in soybean can greatly enhance nitrogen fixation efficiency. Nodule formation in legumes starts with cortical cell divisions in the root. Despite the discovery of the Nod factors and plant hormones that are involved, it remains unclear how cortical cell division is spatiotemporally regulated. Here we provide evidence that soybean has acquired two SHORT-ROOT ( SHR ) paralogs during evolution, which are specifically induced in the early stage of nodule organogenesis. These SHR homologs can activate the expression of early nodulin genes and enhance cytokinin signaling and form part of a multilevel regulatory network to activate D-type cyclins during nodulation. Our results provide insight into the mechanisms of nodule organogenesis in soybean.