Esperanza Martinez's research while affiliated with Universidad Nacional Autónoma de México and other places

Publications (6)

Article
Using a modified Eckhardt method, we visualized replicons larger than 1,000 kb in Rhizobium tropici strains belonging to both subgroup A and subgroup B. The megaplasmid of R. tropici CFN299 was characterized. This megaplasmid is different from a cointegrate of various plasmids and from the chromosome. Hybridization of Eckhardt blots of 15 R. tropic...
Article
Full-text available
Agrobacterium transconjugants containing symbiotic plasmids from different Rhizobium spp. strains that nodulate Phaseolus vulgaris were obtained. All transconjugants conserved the parental nodulation host range. Symbiotic (Sym) plasmids of Rhizobium strains isolated originally from P. vulgaris nodules, which had a broad nodulation host range, and s...
Chapter
In the last few years we have directed our research efforts towards the understanding of the nature of Rhizobium phaseoli and its genome, in particular those features that could be relevant for its symbiotic properties. At the present time we are addresing some questions that we consider relevant to obtain an overall view of the organization of the...
Chapter
The bacteria belonging to the genus Rhizobium establish symbiosis with the roots of legumes. The symbiotic process involves the differentiation of both bacteria and plant cells. A specialized organ, the nodule, is formed in which nitrogen is fixed by the bacterial nitrogenase. The symbiotic interaction is specific and Rhizobium “species” have been...
Chapter
Bean, Phaseolus vulgaris, had its origin and diversified in Mexico. To evaluate nitrogen fixation we collected data of fertilization assays carried out in agricultural areas of Mexico during the last five years by different institutions: National Institute of Agricultural Research, INIA; Postgraduate College of Chapingo, University of Morelos State...

Citations

... R. leguminosarum bv. phaseoli is a very heterogeneous group of bacteria (Beynon and Josey, 1980;Martinez and Palacios, 1984;Roberts et al., 1980) and two types have been identified (Martinez et al., 1985). Symbiotype 1 is characterized by a lim- * FAX No.: 202 3601036. ...
... phaseoli are distinctive and markedly diverse genetically (28). Native isolates recovered from bean nodules also vary in their nodulation host range and in nitrogenase (nif) gene copy number (24,27). Consistent with the data from twodimensional polyacrylamide gel electrophoresis of total proteins, Young (35) observed considerable sharing of electrophoretic mobility variants of three metabolic enzymes between isolates of R. leguminosarum bv. ...
... 39% of the Rlv UPM791 (Sánchez-Cañizares et al. 2018) and up to 45% of the R. etli genomes (Martínez-Romero 1994). In Rhizobium, most of the essential genes required for the formation of a nitrogen-fixing nodule (i.e., nod, nif, and fix) are carried on large plasmids called symbiotic plasmids or pSym (Martínez et al. 1990). Symbiotic genes are not always located on the same plasmid; other plasmids can be involved in the symbiotic process (Hynes and McGregor 1990). ...
... The plasmids may carry genes encoding traits beneficial for the organism's survival, for example, resistance to antibiotics or to heavy metals. Usually the plasmid size is relatively small but in some cases plasmids are comparable in size to the chromosome, like the megaplasmid in Rhizobium tropici (Geniaux et al., 1995). ...
... Se han reclasificado a algunas cepas previamente consideradas como R. etli en otras especies cercanas, R. phaseoli (Ramírez-Bahena et al., 2008), R. ecuadorense (Ribeiro et al., 2015) y R. esperanzae (Cordeiro et al., 2017), mientras otros linajes nuevos no han sido todavía nombrados como nuevas especies (López- Guerrero et al., 2012). Es notable que distintas especies de rizobios con capacidad de formar nódulos en P. vulgaris comparten un plásmido simbiótico conservado que representa al simbiovar phaseoli o tropici, lo que indica que los plásmidos pueden transferirse entre rizobios en condiciones naturales (Cao et al., 2014), y se ha confirmado en experimentos de laboratorio (Brom et al., 1988;Martínez et al., 1987;Rogel et al., 2001). Es importante aclarar que el término simbiovar sustituyó al de biovar y refleja la especificidad del rizobio por la planta (Rogel et al., 2011). ...