Image_1_The PGPR Bacillus aryabhattai promotes soybean growth via nutrient and chlorophyll maintenance and the production of butanoic acid.tif

Plant growth-promoting rhizobacteria (PGPR) colonize plant roots, establish a mutualistic relationship with the plants and help them grow better. This study reports novel findings on the plant growth-promoting effects of the PGPR Bacillus aryabhattai. Soil was collected from a soybean field, PGPR were isolated, identified, and characterized for their ability to promote plant growth and development. The bacterium was isolated from the soybean rhizosphere and identified as B. aryabhattai strain SRB02 via 16s rRNA sequencing. As shown by SEM, the bacterium successfully colonized rice and soybean roots within 2 days and significantly promoted the growth of the GA-deficient rice cultivar Waito-C within 10 days, as well as the growth of soybean plants with at least six times longer shoots, roots, higher chlorophyll content, fresh, and dry weight after 10 days of inoculation. ICP analysis showed up to a 100% increase in the quantity of 18 different amino acids in the SRB02-treated soybean plants. Furthermore, the 2-DE gel assay indicated the presence of several differentially expressed proteins in soybean leaves after 24 hrs of SRB02 application. MALDI-TOF-MS identified β-conglycinin and glycinin along with several other proteins that were traced back to their respective genes. Analysis of bacterial culture filtrates via GCMS recorded significantly higher quantities of butanoic acid which was approximately 42% of all the metabolites found in the filtrates. The application of 100 ppm butanoic acid had significantly positive effects on plant growth via chlorophyll maintenance. These results establish the suitability of B. aryabhattai as a promising PGPR for field application in various crops.</p

Table_1_The PGPR Bacillus aryabhattai promotes soybean growth via nutrient and chlorophyll maintenance and the production of butanoic acid.docx

Plant growth-promoting rhizobacteria (PGPR) colonize plant roots, establish a mutualistic relationship with the plants and help them grow better. This study reports novel findings on the plant growth-promoting effects of the PGPR Bacillus aryabhattai. Soil was collected from a soybean field, PGPR were isolated, identified, and characterized for their ability to promote plant growth and development. The bacterium was isolated from the soybean rhizosphere and identified as B. aryabhattai strain SRB02 via 16s rRNA sequencing. As shown by SEM, the bacterium successfully colonized rice and soybean roots within 2 days and significantly promoted the growth of the GA-deficient rice cultivar Waito-C within 10 days, as well as the growth of soybean plants with at least six times longer shoots, roots, higher chlorophyll content, fresh, and dry weight after 10 days of inoculation. ICP analysis showed up to a 100% increase in the quantity of 18 different amino acids in the SRB02-treated soybean plants. Furthermore, the 2-DE gel assay indicated the presence of several differentially expressed proteins in soybean leaves after 24 hrs of SRB02 application. MALDI-TOF-MS identified β-conglycinin and glycinin along with several other proteins that were traced back to their respective genes. Analysis of bacterial culture filtrates via GCMS recorded significantly higher quantities of butanoic acid which was approximately 42% of all the metabolites found in the filtrates. The application of 100 ppm butanoic acid had significantly positive effects on plant growth via chlorophyll maintenance. These results establish the suitability of B. aryabhattai as a promising PGPR for field application in various crops.</p

Shoot length and fresh weight of rice seedlings in response to SA application (0.5 and 1.0 mM) in the presence and absence of salt stress (100 mM).

<p>Shoot length and fresh weight of rice seedlings in response to SA application (0.5 and 1.0 mM) in the presence and absence of salt stress (100 mM).</p

Effects of single application of SA or NaCl, and combination treatment of SA and NaCl on <i>OsCATA</i> expression in rice plants.

<p>Lowercase letters indicate a significant difference among treatments. Vertical bars with error bars indicate the average ± standard error (n = 3), and different letters indicate a significance difference at P < 0.05. All data were analyzed by DMRT.</p

Effects of single application of SA or NaCl, and combined treatment of SA and NaCl on the mRNA expression of <i>OsGSNOR</i>, <i>OsNIR</i>, and <i>OsNOA</i> in rice plants.

<p>Lowercase letters indicate a significant difference among treatments. DAT (days after treatment) refers to the period of SA and NaCl exposure. Vertical bars with error bars indicate the average ± standard error (n = 3), and different letters indicate a significant difference at P < 0.05. All data were analyzed by DMRT.</p

Changes in chlorophyll fluorescence and the electric conductivity ratio after combination treatment of rice plants with SA and NaCl, and single treatment with SA or NaCl.

<p>A and B indicate changes in chlorophyll fluorescence and the EC ratio during different treatment times, respectively. Each symbol indicates the average, and the bar indicates ± standard error (n = 3).</p

Effects of single application of SA or NaCl, and combination treatment of SA and NaCl on <i>OsAPX1</i> expression in rice plants.

<p>Lowercase letters indicate a significant difference among treatments. Vertical bars with error bars indicate the average ± standard error (n = 3), and different letters indicate significant differences at P < 0.05. All data were analyzed by DMRT.</p

Effect of combined treatment with SA and NaCl for 4 days on phenotypic changes in rice plants.

<p>Arabic numbers indicate each treatment (1: control, 2: 0.5 mM SA, 3: 1.0 mM SA, 4: 0.5 mM SA + 100 mM NaCl, 5: 1.0 mM SA + 100 mM NaCl, 6: 100 mM NaCl) and capital letters indicate different treatment periods (A: 1 day, B: 2 days, C: 3 days, D: 4 days). The white vertical bar in the figure represents 10 cm.</p

Sodium ions and SA content of rice seedlings in response to SA application (0.5 and 1.0 mM) in the presence and absence of salt stress (100 mM).

<p>Sodium ions and SA content of rice seedlings in response to SA application (0.5 and 1.0 mM) in the presence and absence of salt stress (100 mM).</p

Pearson’s correlation coefficient among phenotypic data in different stress exposure periods of rice plant.

<p>Pearson’s correlation coefficient among phenotypic data in different stress exposure periods of rice plant.</p