Analysis of functional redundance of Rieske subunit in cytochrome bc complex of Mesorhizobium loti

LAURA A. BASILE; VIVIANA C. LEPEK

Cordoba

Congreso; LII Reunion Anual SAIB; 2016

Nodule development in rhizobia-legumes symbiosis leads to drastic changes in both plant and bacteria as result of the interaction. Bacterial respiratory chain ismodified allowing nitrogenase activity, being the cytochrome bc complex a key component of this chain. Its Rieske Fe/S subunit has a signal for TAT secretionsystem. M. loti has two Rieske subunits: mll2707 and mlr0970. In this work we proposed to analyze if there are functional redundance for cytochrome bc. By fusionof promoter region to β-gal we only detected activity of 2707. However, when microoxid conditions were simulated, 0970 activity was also observed. Gene expressionwas determined by qPCR, both in M. loti wt and a TAT deficient strain (tatC). 2707 mRNA levels exceeded those of 0970. In microoxid conditions this relationwas inverted, detecting higher levels of 0970 in both strains. In order to test protein stability, 2707 and 0970 were fused to a flag and constitutively expressed forWestern detection. High levels of 2707 were observed in wt, both at high and low oxygen, and inside the nodule. However, it was absent in tatC, suggesting thata functional TAT system is required for the stability of the protein. 0970 was detected in tatC only at low oxygen. We have constructed mutants of M. loti in 2707,0970 and double mutant. Their role in nodulation will be determined by inoculation of these strains in Lotus tenuis plants