Degradation of trehalose-6-phosphate can be mediated by a trehalose 6-phosphate hydrolase (TreC), belonging to family 13 of glycoside hydrolases [16], or a trehalose-6-phosphate phosphorylase (TrePP) [19].Trehalase, trehalose phosphorylase, and trehalose-6-phosphate PF-04929113 research buy hydrolase were detected in click here soybean nodules formed by B. japonicum[20], but orthologous genes for these enzymes were not found in the genome of S. meliloti[21]. In the former species, two ABC transport systems (ThuEFGK and AglEFGAK), and one major catabolic pathway (ThuAB) have been reported for trehalose [22, 23]. In rhizobia, the effect of trehalose
accumulation on tolerance to osmotic and drought stress, as well as symbiotic performance, appears to be dependent on the particular stress, the rhizobial species, and the host genotype. Regarding osmotic stress, OtsAB seems to play a major role in trehalose accumulation under hyperosmotic conditions, MK 1775 and it is the main system involved in osmoadaptation of S. meliloti[5] and B. japonicum[2]. In addition, accumulated trehalose seems to have
a major role in protecting B. japonicum[24] and R. leguminosarum bv trifolii[7] against desiccation stress. With respect to symbiotic phenotype, in B. japonicum trehalose accumulation is involved in the development of symbiotic nitrogen-fixing root nodules on soybean plants [2]. In contrast, in other rhizobia such as R. leguminosarum bv trifolii or S. meliloti, trehalose accumulation has been proposed to be important
only for competitiveness [5, 7]. The role of trehalose as thermoprotectant has been established in yeast [25] and bacteria such as E. coli[26], Salmonella enterica serovar Typhimurium [27] or the halophilic bacterium Chromohalobacter salexigens[28]. However the role of trehalose in protection against heat stress in rhizobia has not yet been investigated. Common bean (Phaseolus vulgaris) is an important crop in the diet of people Bay 11-7085 of Latin America. In this region, it is mainly nodulated by R. etli[29]. The complete genome sequence of R. etli CFN 42 has been reported ( http://www.ccg.unam.mx/retlidb/) [30]. It contains more replicons (a circular chromosome and six large plasmids) than any other completely sequenced nitrogen-fixing bacterium, but several pieces of evidence suggest an exogenous origin for plasmids p42a and p42d Suarez and co-workers [10] reported an otsA mutant still capable of accumulating trehalose to a certain extent, which was nevertheless osmosensitive and displayed reduced nodulation and lower nitrogenase activity, and consequently reduced plan biomass. In contrast, an OtsA overexpressing R. etli strain showed increased trehalose content and was more tolerant to osmotic stress than the wild-type. Bean plants inoculated with the OtsA overexpressing strain showed improved nodulation and nitrogen fixation, and increased drought tolerance.