The comparison of structural genes expression of nitrogenase and enzymes activity related to its performance in chickpea nodules inoculated with two Mesorhizobium species

The symbiotic relationships between chickpea and Mesorhizobia are important for nitrogen symbiotic fixation and also yield potential. The precise identification of physiological and molecular mechanisms involved in contrasting responses in symbiotic effectiveness of symbiotic associations will be used to enhance productivity through genetic engineering and breeding methods. In this study, symbiotic efficiency of chickpea with two Mesorhizobium species (Mesrhizobium ciceri CP-31 and M. mediterraneum SWRI9) were compared based on their growth traits. According to the results, symbiotic efficiency in chickpea- M. mediterraneum SWRI9 symbiosis was higher than chickpea- M. ciceri CP-31 symbiosis because higher content of shoot, root and nodule dry weight and also nodule number in this symbiotic association. This result was confirmed by higher expression level of nifK in chickpea- M. mediterraneum SWRI9 symbiosis. In addition, a noticeable difference in activity of enzymes related to carbon and nitrogen metabolism was observed in nodules of both symbiotic associations. The activity of sucrose synthase, UDP-glucose pyrophosphorylase, malate dehydrogenase, phosphoenol pyruvate carboxylase and NAD-malic enzyme and also key enzymes of oxidative pentose phosphate pathway (glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase) was higher in chickpea- M. mediterraneum SWRI9 symbiosis. A higher activity for enzymes responsible for ammonium assimilation and amino acid biosynthesis (glutamate synthetase, glutamine synthetase, amino acid transpherase and NAD/NADH glutamate dehydrogenase) was observed in nodules of chickpea- M. mediterraneum SWRI9 symbiosis. Collectively, higher symbiotic efficiency of chickpea- M. mediterraneum SWRI9 symbiosis may be associated with higher expression of nifK and also the activity of the key enzymes related to the nodule carbon and nitrogen metabolism