title: Approaches for enhancement of N₂ fixation efficiency of chickpea (Cicer arietinum L.) under limiting nitrogen conditions.
abstract: Chickpea (Cicer arietinum) is an important pulse crop in many countries in the world. The symbioses between chickpea and Mesorhizobia, which fix N₂ inside the root nodules, are of particular importance for chickpea's productivity. With the aim of enhancing symbiotic efficiency in chickpea, we compared the symbiotic efficiency of C-15, Ch-191 and CP-36 strains of Mesorhizobium ciceri in association with the local elite chickpea cultivar 'Bivanij' as well as studied the mechanism underlying the improvement of N₂ fixation efficiency. Our data revealed that C-15 strain manifested the most efficient N₂ fixation in comparison with Ch-191 or CP-36. This finding was supported by higher plant productivity and expression levels of the nifHDK genes in C-15 nodules. Nodule specific activity was significantly higher in C-15 combination, partially as a result of higher electron allocation to N₂ versus H⁺. Interestingly, a striking difference in nodule carbon and nitrogen composition was observed. Sucrose cleavage enzymes displayed comparatively lower activity in nodules established by either Ch-191 or CP-36. Organic acid formation, particularly that of malate, was remarkably higher in nodules induced by C-15 strain. As a result, the best symbiotic efficiency observed with C-15-induced nodules was reflected in a higher concentration of the total and several major amino metabolites, namely asparagine, glutamine, glutamate and aspartate. Collectively, our findings demonstrated that the improved efficiency in chickpea symbiotic system, established with C-15, was associated with the enhanced capacity of organic acid formation and the activities of the key enzymes connected to the nodule carbon and nitrogen metabolism.
authors.affiliation: Department of Biology, Faculty of Sciences, Lorestan University, Khorramabad, Iran.
authors.forename: Maryam Nasr
authors.initials: MN
authors.lastname: Esfahani
authors.forename: Saad
authors.initials: S
authors.lastname: Sulieman
authors.forename: Joachim
authors.initials: J
authors.lastname: Schulze
authors.forename: Kazuko
authors.initials: K
authors.lastname: Yamaguchi-Shinozaki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shinozaki
authors.forename: Lam-Son
authors.initials: LS
authors.lastname: Tran
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism; D029863:Cicer / Q000201:enzymology / Q000378:metabolism* / Q000382:microbiology; D008293:Malates / Q000378:metabolism; D059128:Mesorhizobium / Q000201:enzymology / Q000502:physiology*; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000378:metabolism / Q000382:microbiology; D018520:Plant Shoots / Q000201:enzymology / Q000378:metabolism / Q000382:microbiology; D053204:Root Nodules, Plant / Q000201:enzymology / Q000378:metabolism / Q000382:microbiology; D013045:Species Specificity; D013395:Sucrose / Q000378:metabolism; D013559:Symbiosis
chemical_list: D008293:Malates; D013395:Sucrose; D002244:Carbon; C030298:malic acid; D009591:Nitrogenase; D009584:Nitrogen
keywords: C-metabolism; Cicer arietinum; Mesorhizobium ciceri; N-metabolism; gene expression; symbiotic efficiency