Characterization of genes involved in the autoregulation of nodulation in chickpea (Cicer arietinum L.)

Establishment of an excess number of nodules markedly affects plant growth and development due to overconsumption of photosynthates for nitrogen fixation. Hence, the total root nodule number must be tightly controlled via a negative feedback mechanism (AON) to maintain an optimal nitrogen and carbon  balance in chickpea plants. Chickpea genes whichplay important regulatory roles in root nodulation in chickpea (Cicer arietinum) were identified by aligning these genes with known genes of legumes available at phytozome through BLAST search. Chickpea nodulation genes identified and characterized in this study include CaNFR1/5, CaENOD40, CaNARK, CaRIC1, CaRIC2, CaNIC1, CaRDN1, CaRDN2, CaRDN3, CamiRNA172 and CaNNC1. These genes were orthologous to Medicago truncatula nodulation genes and were significantly expressed by inoculating chickpea plants with Mesorhizobium ciceri analysed by qRT-PCR using RNA isolated from the root and leaf tissues of inoculated chickpea plants at 0, 2, and 6 days after inoculation. Non-inoculated plants served as control. CaNARK genes were expressed in roots and leaves while the rest of the nodulation genes were expressed only in the roots. The nodulation ability of chickpea may be controlled by an internal AON mechanism which involves several genes that are orthologues with other legumes.