Genes commonly involved in acid tolerance are not overexpressed in the plant microsymbiont Mesorhizobium loti MAFF303099 upon acidic shock

Laranjo, Marta; Alexandre, Ana; Oliveira, Solange

doi:10.1007/s00253-014-5875-4

Cited by 13 publications

(10 citation statements)

References 50 publications

(55 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Interestingly, while there is evidence of acid-tolerant genes in symbiotic rhizobia (Dilworth et al 2001; Glenn et al 1999; Laranjo et al 2014) that permit bacterial survival in Al-rich and low-pH soils supporting growth and N 2 fixation of A. linearis (Muofhe and Dakora 1999), little is known about Al-tolerant genes in legumes and their microsymbionts. This is perhaps not unexpected as no crop species are yet known that tolerate high concentrations of Al in soils.…”

Section: The Aspalathus Linearis Symbiosis: a Natural System For Undementioning

confidence: 99%

Nature and mechanisms of aluminium toxicity, tolerance and amelioration in symbiotic legumes and rhizobia

2018

View full text Add to dashboard Cite

Recent findings on the effect of aluminium (Al) on the functioning of legumes and their associated microsymbionts are reviewed here. Al represents 7% of solid matter in the Earth's crust and is an important abiotic factor that alters microbial and plant functioning at very early stages. The trivalent Al (Al 3+ ) dominates at pH < 5 in soils and becomes a constraint to legume productivity through its lethal effect on rhizobia, the host plant and their interaction. Al 3+ has lethal effects on many aspects of the rhizobia/legume symbiosis, which include a decrease in root elongation and root hair formation, lowered soil rhizobial population, and suppression of nitrogen metabolism involving nitrate reduction, nitrite reduction, nitrogenase activity and the functioning of uptake of hydrogenases (Hup), ultimately impairing the N 2 fixation process. At the molecular level, Al is known to suppress the expression of nodulation genes in symbiotic rhizobia, as well as the induction of genes for the formation of hexokinase, phosphodiesterase, phosphooxidase and acid/alkaline phosphatase. Al toxicity can also induce the accumulation of reactive oxygen species and callose, in addition to lipoperoxidation in the legume root elongation zone. Al tolerance in plants can be achieved through over-expression of citrate synthase gene in roots and/or the synthesis and release of organic acids that reverse Al-induced changes in proteins, as well as metabolic regulation by plant-secreted microRNAs. In contrast, Al tolerance in symbiotic rhizobia is attained via the production of exopolysaccharides, the synthesis of siderophores that reduce Al uptake, induction of efflux pumps resistant to heavy metals and the expression of metal-inducible (dmeRF) gene clusters in symbiotic Rhizobiaceae. In soils, Al toxicity is usually ameliorated through liming, organic matter supply and use of Al-tolerant species. Our current understanding of crop productivity in high Al soils suggests that a much greater future accumulation of Al is likely to occur in agricultural soils globally if crop irrigation is increased under a changing climate.

show abstract

Section: The Aspalathus Linearis Symbiosis: a Natural System For Undementioning

confidence: 99%

Nature and mechanisms of aluminium toxicity, tolerance and amelioration in symbiotic legumes and rhizobia

2018

View full text Add to dashboard Cite

show abstract

“…Global response to acid pH remains less studied, nevertheless the available reports indicate, once again, that different rhizobia may show little similarities on their acid transcriptional profile [39],[40],[41]. While in S. meliloti , exposure to acid pH lead to a strong upregulation of genes involved in exopolysaccharide biosynthesis as well as a general downregulation of genes related to motility and chemotaxis [40], in M. japonicum these genes remained mostly unchanged [39]. In both strains, genes involved in ABC transporter systems were overexpressed, with higher numbers in the case of M. japonicum .…”

Section: Stress Response Genesmentioning

confidence: 99%

“…For example, from the six plasmids included in the R. etli CE3 genome, four were found to be highly over-represented in the response to heat shock, while most genes overexpressed after a saline shock were chromosomal and encoded in a fifth different plasmid [32]. In addition, stress response may also differ in similar organisms with different levels of tolerance to the imposed stress [39]. These global transcriptional analyses (using microarrays or RNAseq) also demonstrate that there is still a high percentage of genes of unknown function, whose expression responds to environmental perturbations, and that might have an important role on survival to stress.…”

Section: Stress Response Genesmentioning

confidence: 99%

Can stress response genes be used to improve the symbiotic performance of rhizobia?

2017

Self Cite

View full text Add to dashboard Cite

Rhizobia are soil bacteria able to form symbioses with legumes and fix atmospheric nitrogen, converting it into a form that can be assimilated by the plant. The biological nitrogen fixation is a possible strategy to reduce the environmental pollution caused by the use of chemical N-fertilizers in agricultural fields. Successful colonization of the host root by free-living rhizobia requires that these bacteria are able to deal with adverse conditions in the soil, in addition to stresses that may occur in their endosymbiotic life inside the root nodules. Stress response genes, such as otsAB , groEL , clpB , rpoH play an important role in tolerance of free-living rhizobia to different environmental conditions and some of these genes have been shown to be involved in the symbiosis. This review will focus on stress response genes that have been reported to improve the symbiotic performance of rhizobia with their host plants. For example, chickpea plants inoculated with a Mesorhizobium strain modified with extra copies of the groEL gene showed a symbiotic effectiveness approximately 1.5 fold higher than plants inoculated with the wild-type strain. Despite these promising results, more studies are required to obtain highly efficient and tolerant rhizobia strains, suitable for different edaphoclimatic conditions, to be used as field inoculants.

show abstract

“…In a transcriptome analysis of M . loti MAFF303099 submitted to an acidic shock, a very slight underexpression of clpB gene was detected [ 54 ]. Therefore, more studies are required in order to clarify the ClpB involvement in Mesorhizobium tolerance to acidity.…”

Section: Discussionmentioning

confidence: 99%

The Symbiotic Performance of Chickpea Rhizobia Can Be Improved by Additional Copies of the clpB Chaperone Gene

et al. 2016

Self Cite

View full text Add to dashboard Cite

The ClpB chaperone is known to be involved in bacterial stress response. Moreover, recent studies suggest that this protein has also a role in the chickpea-rhizobia symbiosis. In order to improve both stress tolerance and symbiotic performance of a chickpea microsymbiont, the Mesorhizobium mediterraneum UPM-Ca36T strain was genetically transformed with pPHU231 containing an extra-copy of the clpB gene. To investigate if the clpB-transformed strain displays an improved stress tolerance, bacterial growth was evaluated under heat and acid stress conditions. In addition, the effect of the extra-copies of the clpB gene in the symbiotic performance was evaluated using plant growth assays (hydroponic and pot trials). The clpB-transformed strain is more tolerant to heat shock than the strain transformed with pPHU231, supporting the involvement of ClpB in rhizobia heat shock tolerance. Both plant growth assays showed that ClpB has an important role in chickpea-rhizobia symbiosis. The nodulation kinetics analysis showed a higher rate of nodule appearance with the clpB-transformed strain. This strain also induced a greater number of nodules and, more notably, its symbiotic effectiveness increased ~60% at pH5 and 83% at pH7, compared to the wild-type strain. Furthermore, a higher frequency of root hair curling was also observed in plants inoculated with the clpB-transformed strain, compared to the wild-type strain. The superior root hair curling induction, nodulation ability and symbiotic effectiveness of the clpB-transformed strain may be explained by an increased expression of symbiosis genes. Indeed, higher transcript levels of the nodulation genes nodA and nodC (~3 folds) were detected in the clpB-transformed strain. The improvement of rhizobia by addition of extra-copies of the clpB gene may be a promising strategy to obtain strains with enhanced stress tolerance and symbiotic effectiveness, thus contributing to their success as crop inoculants, particularly under environmental stresses. This is the first report on the successful improvement of a rhizobium with a chaperone gene.

show abstract

Genes commonly involved in acid tolerance are not overexpressed in the plant microsymbiont Mesorhizobium loti MAFF303099 upon acidic shock

Cited by 13 publications

References 50 publications

Nature and mechanisms of aluminium toxicity, tolerance and amelioration in symbiotic legumes and rhizobia

Nature and mechanisms of aluminium toxicity, tolerance and amelioration in symbiotic legumes and rhizobia

Can stress response genes be used to improve the symbiotic performance of rhizobia?

The Symbiotic Performance of Chickpea Rhizobia Can Be Improved by Additional Copies of the clpB Chaperone Gene

Contact Info

Product

Resources

About