The soybean CEP6 signaling peptides positively regulates nodulation

Abstract Nodulation is the most efficient nitrate assimilation system in the ecosystem while excessive fertilization increased nitrate inhibition effect, deciphering the nitrate signal transduction mechanism in the process is of the utmost importance. In this study, genome-wide analysis of the GmCEP genes were applied to identify nodulation related CEPgenes, 22 GmCEP family members were identified while GmCEP6 mainly expressed in nodule and significantly responded to nitrate treatment and rhizobium infection, especially in later stages. Overexpression and CRISPR-Cas9 were used to validate its role in nodulation. We found GmCEP6overexpression significantly increased the nodule number while GmCEP6knock out significantly decreased nodule number suggests GmCEP6 function as a positive regulator in soybean nodulation. qRT-PCR shown that alterations in the expression of GmCEP6 affected the expression of marker genes in the Nod factor signaling pathway. Lastly the function of GmCEP6 in nitrate inhibition of nodulation was analyzed, nodule number in the GmCEP6 overexpressed roots significantly increased under nitrogen treatments suggests GmCEP6 functions in resistance to nitrate inhibition. The study will help us understand that GmCEP6 promotes nodulation and participates in the regulation of nitrate inhibition of nodulation, which is of great significance for high efficiency utilization of nitrogen in soybean.