Project description:Investigation of whole genome gene expression level changes in a Sinorhizobium meliloti 1021 rpoH1 rpoH2 double mutant, compared to the wild-type strain. The mutations engineered into this strain render it deficient in symbiotic nitrogen fixation. The mutants analyzed in this study are further described in Mitsui, H, T. Sato, Y. Sato, and K. Minamisawa. 2004. Sinorhizobium meliloti RpoH1 is required for effective nitrogen-fixing symbiosis with alfalfa. Mol Gen Genomics 271:416-425.
Project description:Nitrogen (N) and phosphorus (P) are the most limiting factors for plant growth. Some microorganisms improve the uptake and availability of N and P, minimizing chemical fertilizer dependence. It has been published that the RD64 strain, a Sinorhizobium meliloti 1021 strain engineered to overproduce indole-3-acetic acid (IAA), showed improved nitrogen fixation ability as compared to the wild type 1021 strain. We present here data showing that RD64 is also highly effective in mobilizing P from insoluble sources such as phosphate rock (PR). Under P-limiting conditions, the higher P-mobilizing activity of RD64, as compared to the 1021 wild type strain, is connected with the up-regulation of genes coding for the high-affinity P transport system, the induction of acid phosphatase activity and the increased secretion into the growth media of malic, succinic and fumaric acids. Medicago truncatula plants nodulated by RD64 (Mt-RD64), when grown under P-deficient conditions, released higher amounts of another P-solubilizing organic acid, the 2-hydroxyglutaric acid, as compared to the plants nodulated by the wild-type strain (Mt-1021). It has already been shown that Mt-RD64 plants exhibited a higher dry weight production as compared to Mt-1021 plants. Here we report that also P-starved Mt-RD64 plants show a significant increase both in shoot and root fresh weight when compared to P-starved Mt-1021 plants. We discuss how, in a rhizobium-legume model system, a balanced interplay of different factors linked to the bacterial IAA over-production rather than IAA production per se stimulates plant growth under stressful environmental conditions, and in particular, under P-starvation. Two-conditions experiment: untreated 1021 vs. 2,4-D-treated 1021 cells. Biological replicates: 6 untreated controls, 6 treated samples, independently grown and harvested. One replicate per array.
Project description:Nitrogen (N) and phosphorus (P) are the most limiting factors for plant growth. Some microorganisms improve the uptake and availability of N and P minimizing chemical fertilizers dependence. It has been published that the RD64 strain, a Sinorhizobium meliloti 1021 strain engineered to overproduce indole-3-acetic acid (IAA), showed improved nitrogen fixation ability as compared to the wild type 1021 strain. We present here data showing that RD64 is also highly effective in mobilizing P from insoluble sources such as phosphate rock (PR). Under P-limiting conditions, the higher P-mobilizing activity of RD64, as compared to 1021 wild type strain, is connected with the up-regulation of genes coding for the high-affinity P transport system, the induction of acid phosphatase activity and the increased secretion into the growth media of malic, succinic and fumaric acids. Medicago truncatula plants nodulated by RD64 (Mt-RD64), when grown under P deficient conditions, released higher amounts of another P-solubilizing organic acid, the 2-hydroxyglutaric acid, as compared to the plants nodulated by the wild-type strain (Mt-1021). It has already been shown that Mt-RD64 plants exhibited a higher dry weight production as compared to Mt-1021 plants. Here we report that also P-starved Mt-RD64 plants show a significant increase both in shoot and root fresh weight when compared to P-starved Mt-1021 plants. We discuss how, in a rhizobium-legume model system, a balanced interplay of different factors linked to the bacterial IAA over-production rather than IAA production per se stimulates plant growth under stressful environmental conditions, and in particular, under P-starvation. Two-conditions experiment: untreated 1021 vs. untreated RD64 cells. Biological replicates: 6 untreated control strain, 6 untreated IAA-overproducing strain, independently grown and harvested. One replicate per array.