Emerging functions of nodulin-like proteins in non-nodulating plant species

Plant genes whose expression is induced in legumes by Rhizobium bacteria upon nodulation were initially referred to as nodulins. Several of them play a key role in the establishment of symbiosis. Yet, nodulin-like proteins are also found in non-nodulating plant species such as Arabidopsis, rice, maize or poplar. For instance, 132 are predicted in the Arabidopsis thaliana Col-0 genome. Recent studies now highlight the importance of nodulin-like proteins for the transport of nutrients, solutes, amino acids or hormones and for major aspects of plant development. Interestingly, nodulin-like activities at the plant-microbe interface are also important for pathogens to enhance their fitness during host colonization. This work presents a genomic and functional overview of nodulin-like proteins in non-leguminous plant species, with a particular focus on Arabidopsis and rice.