Study of temporal and spatial expression of purine permease Pup1 in Medicago truncatula using in situ RNA-RNA hybridization

Abstract

Molecular nitrogen (N2) is the most abundant element in the atmosphere, but not in a form that can be directly assimilated by the plants. Thus, nitrogen is a significant limiting factor for plant development and productivity. The symbiotic interaction between legumes and rhizobia, resulting to the reduction of the atmospheric nitrogen into ammonia, has been considered one of the linchpins of sustainable agriculture for many centuries. There is substantial evidence, for example, data bioinformatics analysis and functional genomics that in certain types of symbiotic nitrogen fixation, rhizobia need nucleotide bases, particularly purines. The study of the role of purines and their transport system from the host plant in rhizobium will result in a better understanding of the molecular and biochemical mechanisms underlining symbiotic nitrogen fixation and improve our ability for the genetic manipulation of this beneficial interaction. In the present study, an in situ RNA-RNA hybridization approach was performed in order to determine the temporal and spatial expression of purine permease Pup1 gene during the different stages of Medicago truncatula nodule development. In situ RNA-RNA hybridization revealed a strong expression of the purine permease Pup1 gene during nodule development. Specifically, purine permease Pup1 gene transcripts shared a similar spatial expression pattern in nodules at all developmental stages examined and were localized in the central tissue, the vascular bundles and the nodule parenchyma in nodules at 14, 21 and 28 days post inoculation.