INVESTIGADORES
CASTAGNO Luis nazareno
congresos y reuniones científicas
Título:
Plasmid profiles of rhizobia nodulating Lotus tenuis in different soils of the flooding Pampa
Autor/es:
SANNAZZARO AI; CASTAGNO LN; RUIZ OA; PISTORIO M; TORRES TEJERIZO G; LAGARES A; ESTRELLA MJ
Lugar:
Bariloche
Reunión:
Congreso; International Plasmid Biology Conference 2010; 2010
Resumen:
Background and aims: The utilization of Lotus
tenuis to obtain a high productivity of pastures in soils of the
Flooding Pampa (FP, Buenos Aires, Argentina) becomes a very relevant
topic for cattle production; in view of that region have restrictive
soils that limit the growth of traditional legumes such as clover and
lucerne. In a previous study we have taxonomically characterized native
rizobia isolated from L. tenuis in constrained environments of the FP
(Estrella et al., 2009). Some of these strains have been screened and
selected for their superior symbiotic N2-fixing abilities under
laboratory conditions and could be useful to increase the yield of L.
tenuis (Sannazzaro et al., 2010). A majority of these isolates were
related to species of the genera Mesorhizobium and Rhizobium.While in
Mesorhizobium spp. the genes required for symbiosis are usually located
on chromosomal symbiotic islands, in,Rhizobium spp. the homolog genes
are located on (mega) plasmids. However, most rhizobia have in addition
cryptic plasmids that, though not essential for the establishment of
symbiosis, can modulate the interaction between the symbionts by
changing nodulation efficiency, competitiveness, or adaptation and
survival under different environmental conditions. This work presents a
preliminary survey on the occurrence of cryptic plasmids in native
rhizobia isolated from L. tenuis growing in the FP. Methods: Rhizobial
strains used in this work belong to a previously characterized
collection of isolates recovered from nodulated L. tenuis from the FP
(Estrella et al. 2009). Plasmids of rhizobia were separated on
horizontal agarose gels by following the in situ lisis procedure
described by Eckhardt (1978).Results and conclusions: The number of
plasmids varied between zero and five, with most strains containing
only one plasmid. The comparison of infective and non-infective
isolates revealed no evident correlation between this trait and
particular plasmid profiles. Similarly, the presence of plasmids could
not be associated with any particular stress tolerance. These
preliminary results encourage us to further explore the presence of
plasmid-borne genes involved in the symbiosis with L. tenuis and/or
environmental adaptative functions.