Nod factors have been known for decades as signalling molecules produced by rhizobia to trigger and enable dinitrogen-fixing symbiosis. In their new studies, the researchers reveal for the first time that a developmental switch in the legume plant is ensured by the host-controlled modulation of microbial morphogen, Nod factor.ĭeepening our understanding of Nod factor signalling The nitrogen-fixing root nodules are lateral organs induced by a microbial morphogen. Molecules of microbial nature have also been shown to induce a morphogenetic response in symbiotic eukaryotic hosts, and recently gained an increased attention via microbiome studies.

The crucial role of self-produced morphogens like retinoic acid or transformation growth factor-beta during embryo development has been long demonstrated. Morphogens are key signals for organized development in multicellular organisms. Their work reveals a new and crucial role of the legume host in modulating levels of specific rhizobial Nod factor morphogens during cortical infection to ensure functional symbiosis. More specifically, in their new studies, the researchers found that the chitinase CHIT5 present in legume roots is required for Nod factor hydrolysis and functional symbiosis. The researchers wanted to transfer this symbiotic process to other types of plants. The bacteria provide the plant host with reduced nitrogen in the form of ammonia, and the plants can therefore grow without chemical nitrogen fertilizer. This interaction is dependent on plant recognition of a bacterial Nod factor signal molecule. Legumes have evolved the ability to host nitrogen-fixing bacteria within special organs in their roots.

Goldilocks just right