Compact Root Architecture 2 Promotes Root Competence for Nodulation through the miR2111 Systemic Effector
Nitrogen-deprived legume plants form new root organs, the nodules, following a symbiosis with nitrogen-fixing rhizobial bacteria [1]. Because this interaction is beneficial for the plant but has a high energetic cost, nodulation is tightly controlled by host plants through systemic pathways (acting...
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Veröffentlicht in: | Current biology 2020-04, Vol.30 (7), p.1339-1345.e3 |
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Zusammenfassung: | Nitrogen-deprived legume plants form new root organs, the nodules, following a symbiosis with nitrogen-fixing rhizobial bacteria [1]. Because this interaction is beneficial for the plant but has a high energetic cost, nodulation is tightly controlled by host plants through systemic pathways (acting at long distance) to promote or limit rhizobial infections and nodulation depending on earlier infections and on nitrogen availability [2]. In the Medicago truncatula model legume, CLE12 (Clavata3/Embryo surrounding region 12) and CLE13 signaling peptides produced in nodulated roots act in shoots through the SUNN (Super Numeric Nodule) receptor to negatively regulate nodulation and therefore autoregulate nodule number [3–5]. Conversely, CEP (C-terminally Encoded Peptide) signaling peptides produced in nitrogen-starved roots act in shoots through the CRA2 (Compact Root Architecture 2) receptor to promote nodulation already in the absence of rhizobia [6–9]. We show in this study that a downstream shoot-to-root signaling effector of these systemic pathways is the shoot-produced miR2111 microRNA [10] that negatively regulates TML1 (Too Much Love 1) and TML2 [11] transcripts accumulation in roots, ultimately promoting nodulation. Low nitrogen conditions and CEP1 signaling peptides induce in the absence of rhizobia the production of miR2111 depending on CRA2 activity in shoots, thus favoring root competence for nodulation. Together with the SUNN pathway negatively regulating the same miR2111 systemic effector when roots are nodulated, this allows a dynamic fine-tuning of the nodulation capacity of legume roots by nitrogen availability and rhizobial cues.
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•The miR2111 microRNA positively regulates root symbiotic nodulation•This regulation is systemic from shoots and relies on the CRA2 receptor•CRA2-related CEP1 peptides and low nitrogen conditions promote miR2111 expression•The CEP/CRA2 pathway favors root competence to nodulate under low nitrogen
Legumes form symbiotic nitrogen-fixing root nodules, whose number is controlled by systemic pathways acting from shoots. Gautrat et al. show that the miR2111 microRNA is a systemic effector acting at the crossroads of the SUNN-negative and CRA2-positive pathways, allowing a dynamic fine-tuning of nodulation by nitrogen and symbiotic rhizobia. |
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ISSN: | 0960-9822 1879-0445 |
DOI: | 10.1016/j.cub.2020.01.084 |