Gene expression profiles of a Si- norhizobium meliloti 1021 nifA mutant and wild type nodule bacteria were compared using whole genome microarrays. The results revealed a large scale al- teration of gene expression (6...Gene expression profiles of a Si- norhizobium meliloti 1021 nifA mutant and wild type nodule bacteria were compared using whole genome microarrays. The results revealed a large scale al- teration of gene expression (601 genes) in the nifA minus background. The loss of NifA altered the ex- pression of many functional groups of genes (mac- romolecular metabolism, TCA cycle and respiration, nodulation and nitrogen fixation) and may lead to quite different life stages of the nodule bacteria. Upregulation of fixK and its associated genes was observed in the nifA mutant nodule bacteria. Addi- tional quantitative real-time PCR experiments re- vealed that the transcript levels of fixLJ were signifi- cantly upshifted in the nifA mutant nodule bacteria. Putative NifA binding sites were predicted by a statis- tical method in the upstream sequences of 13 differ- entially regulated genes from the nifA- transcriptome.展开更多
To search for an alternative to alfalfa under conditions of salinity and drought, a comparative study was carried out to explore the effect of salinity on the symbiosis of alfalfa and local esparcet species (Onobrychi...To search for an alternative to alfalfa under conditions of salinity and drought, a comparative study was carried out to explore the effect of salinity on the symbiosis of alfalfa and local esparcet species (Onobrychis transcaucasica and Onobrychis chorassanica) inoculated with their nodule bacteria. The salinity of up to 30 mM NaCl insignificantly affected the biomass growth of shoots and roots of alfalfa plants, but the increase in the salinity from 30 to as high as 140 mM NaCl led to the biomass decrease. The salinity produced a double effect on the nodulation process in inoculated alfalfa plants as follows: 1) at 30 - 100 mM NaCl the stimulation of nodulation and increased leghemoglobin activity were observed;2) at salinity concentrations higher than 100 mM NaCl the suppression of both nodule formation and leghemoglobin activity was observed. Alfalfa plants under inoculation with the Sinorhizobium meliloti 10 strain obtained a considerable resistance to salinity (50 - 80 mM NaCl). The efficient symbiosis of O. transcaucasica plants with Rhizobium sp. OT111 and O. chorassanica plants with Rhizobium sp. OC109 enhanced the adaptation of plants to salinity up to 150 mM NaCl. The gradual growth suppression of both Onobrychis plants species started from 200 mM NaCl, and salinity concentration 300 mM NaCl was critical (sublethal) for plants independently of inoculation by nodule bacteria. In field conditions, O. chorassanica was more resistant to salinity than O. transcaucasica, but minimal irrigation for both species of Onobrychis showed a higher effect on their growth and development than the moderate salinity at the concentration 75 mM NaCl. The lower limit (drought threshold) of drought-resistance of Onobrychis plants was 6% - 8% of soil humidity. In shoot and roots of alfalfa, both Onobrychis plant species subject to salt stress, aldehyde oxidase and xanthine dehydrogenase enzymes and different number of their isoforms as well as their electrophoretic mobilities/activities were found.展开更多
基金This work was supported by the Chinese National Key Program for Basic Research （973） （Grant Nos. 001CB108901 ＆ 001CB108902）the National Natural Science Foundation of China （Grant No. 30470940）+1 种基金 Bundesministerium far Bildung und Forschung Germany （Grant No. 031U213D）Deutsche Forschungsgemeinschaft （Grant No. BIZ 7）.
文摘Gene expression profiles of a Si- norhizobium meliloti 1021 nifA mutant and wild type nodule bacteria were compared using whole genome microarrays. The results revealed a large scale al- teration of gene expression (601 genes) in the nifA minus background. The loss of NifA altered the ex- pression of many functional groups of genes (mac- romolecular metabolism, TCA cycle and respiration, nodulation and nitrogen fixation) and may lead to quite different life stages of the nodule bacteria. Upregulation of fixK and its associated genes was observed in the nifA mutant nodule bacteria. Addi- tional quantitative real-time PCR experiments re- vealed that the transcript levels of fixLJ were signifi- cantly upshifted in the nifA mutant nodule bacteria. Putative NifA binding sites were predicted by a statis- tical method in the upstream sequences of 13 differ- entially regulated genes from the nifA- transcriptome.
文摘To search for an alternative to alfalfa under conditions of salinity and drought, a comparative study was carried out to explore the effect of salinity on the symbiosis of alfalfa and local esparcet species (Onobrychis transcaucasica and Onobrychis chorassanica) inoculated with their nodule bacteria. The salinity of up to 30 mM NaCl insignificantly affected the biomass growth of shoots and roots of alfalfa plants, but the increase in the salinity from 30 to as high as 140 mM NaCl led to the biomass decrease. The salinity produced a double effect on the nodulation process in inoculated alfalfa plants as follows: 1) at 30 - 100 mM NaCl the stimulation of nodulation and increased leghemoglobin activity were observed;2) at salinity concentrations higher than 100 mM NaCl the suppression of both nodule formation and leghemoglobin activity was observed. Alfalfa plants under inoculation with the Sinorhizobium meliloti 10 strain obtained a considerable resistance to salinity (50 - 80 mM NaCl). The efficient symbiosis of O. transcaucasica plants with Rhizobium sp. OT111 and O. chorassanica plants with Rhizobium sp. OC109 enhanced the adaptation of plants to salinity up to 150 mM NaCl. The gradual growth suppression of both Onobrychis plants species started from 200 mM NaCl, and salinity concentration 300 mM NaCl was critical (sublethal) for plants independently of inoculation by nodule bacteria. In field conditions, O. chorassanica was more resistant to salinity than O. transcaucasica, but minimal irrigation for both species of Onobrychis showed a higher effect on their growth and development than the moderate salinity at the concentration 75 mM NaCl. The lower limit (drought threshold) of drought-resistance of Onobrychis plants was 6% - 8% of soil humidity. In shoot and roots of alfalfa, both Onobrychis plant species subject to salt stress, aldehyde oxidase and xanthine dehydrogenase enzymes and different number of their isoforms as well as their electrophoretic mobilities/activities were found.
