MicroRNA 4407 modulates nodulation in soybean by repressing a root‐specific ISOPENTENYLTRANSFERASE (GmIPT3)

Abstract

Summary MicroRNAs (miRNAs) are important regulators of plant biological processes, including soybean nodulation. One miRNA, miR4407, was identified in soybean roots and nodules. However, the function of miR4407 in soybean is still unknown. MiR4407, unique to soybean, positively regulates lateral root emergence and root structures and represses a root‐specific ISOPENTENYLTRANSFERASE (GmIPT3). By altering the expression of miR4407 and GmIPT3, we investigated the role of miR4407 in lateral root and nodule development. Both miR4407 and GmIPT3 are expressed in the inner root cortex and nodule primordia. Upon rhizobial inoculation, miR4407 was downregulated while GmIPT3 was upregulated. Overexpressing miR4407 reduced the number of nodules in transgenic soybean hairy roots while overexpressing the wild‐type GmIPT3 or a miR4407‐resistant GmIPT3 mutant (mGmIPT3) significantly increased the nodule number. The mechanism of miR4407 and GmIPT3 functions was also linked to autoregulation of nodulation (AON), where miR4407 overexpression repressed miR172c and activated its target, GmNNC1, turning on AON. Exogenous CK mimicked the effects of GmIPT3 overexpression on miR172c, supporting the notion that GmIPT3 regulates nodulation by enhancing root‐derived CK. Overall, our data revealed a new miRNA‐mediated regulatory mechanism of nodulation in soybean. MiR4407 showed a dual role in lateral root and nodule development.

Insights into the Early Steps of the Symbiotic Interaction between Soybean (Glycine max) and Sinorhizobium fredii Symbiosis Using Transcriptome, Small RNA, and Degradome Sequencing

“…42 MiR4407 plays a dual role in soybean lateral root and nodule development. 43 The induction of miR399b in nodules can enhance nitrogen fixation and soybean growth. 44 However, the role of miRNAs in symbiotic nitrogen fixation in soybeans affected by S. fredii ttsI remains to be elucidated.…”

“…miR393j-3p regulation of ENOD93 mRNA abundance is a key control point for soybean nodule formation . MiR4407 plays a dual role in soybean lateral root and nodule development . The induction of miR399b in nodules can enhance nitrogen fixation and soybean growth .…”