Are phosphatases involved in the regulation of symbiotic nitrogen fixation under phosphorus deficiency?
Résumé
In this study, we highlight the differential expression of phosphatases (APases) within the nodules of Phaseolus vulgaris under phosphorus (P) deficiency and address whether this expression might influence the nodule conductance to O2 diffusion and the subsequent respiration that supports N2 fixation in legumes. The identification of APases genes expression was performed with in situ RT-PCR methodology in nodules of two P. vulgaris recombinant inbred lines; RIL115 (Pefficient) and RIL147 (P-inefficient) grown in hydroaeroponic culture under deficient versus sufficient P supply. Our results brought the first evidence that phytase, trehalose 6-P phosphatase and fructose 1,6 bisphosphatase were differentially expressed among nodule tissues of the RIL115 and RIL147 and suggested that the abundance of their transcripts in infected cells at the vicinity of inner cortex and in outer cortex cells to be considered as new mechanism by which nodules acclimate to P deficiency. This overexpression under P deficiency coupled with increased correspondent enzyme activities and improved rhizobial use efficiency, N2 fixation and is therefore likely to play an important role in tolerance to low P availability. It is suggested that APases are involved in the osmoregulation of nodule conductance to O2 diffusion that is associated with the adaptation to environmental constraints of nitrogenase activity in the infected N2 fixing central tissues of the nodule.