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.
