Voir la page en français

Finally! A CLE peptide regulating symbiotic nodulation that is induced by nitrate in M. truncatula

The nitrate-induced CLE35 signaling peptide inhibits nodulation through the SUNN receptor and miR2111 repression

Legume plants form nitrogen (N)-fixing symbiotic nodules when mineral N is limiting in soils. As N fixation is energetically costly compared to mineral N acquisition, these N sources, and in particular nitrate, inhibit nodule formation and N fixation. In a new study from the Frugier team at IPS2, published by Moreau et al. in Plant Physiology, a CLAVATA3-like (CLE) signaling peptide, MtCLE35, was identified in the model legume Medicago truncatula as induced locally by high-N environments dependent on the Nodule Inception-Like Protein (NLP) MtNLP1 transcription factor. MtCLE35 inhibits nodule formation by affecting rhizobial infections, depending on the Super Numeric Nodules (MtSUNN) receptor. In addition, high N levels or the ectopic expression of MtCLE35 represses the expression and accumulation of the miR2111 shoot-to-root systemic effector, thus inhibiting its positive effect on nodulation. Conversely, ectopic expression of miR2111 or downregulation of MtCLE35 by RNA interference increased miR2111 accumulation independently of the N environment, and thus partially bypasses the nodulation inhibitory action of nitrate. Overall, these results demonstrate that the MtNLP1-dependent, N-induced MtCLE35 signaling peptide acts through the MtSUNN receptor and the miR2111 systemic effector to inhibit nodulation.

The promoter of the MtCLE35 gene contains Nitrate Responsive Elements (NRE) and MtCLE35 induction by nitrate relies on the NIN-Like Protein 1 (MtNLP1) transcription factor.
The promoter of the MtCLE35 gene contains Nitrate Responsive Elements (NRE) and MtCLE35 induction by nitrate relies on the NIN-Like Protein 1 (MtNLP1) transcription factor.