Overexpression of PGPR responsive chickpea miRNA166 targeting ATHB15 for drought stress mitigation

Water limitation creates drought-like situations and constrains the life cycle of crop plants by modulating their biological processes at physiological, biochemical, and molecular levels. The microbial measures, including plant growth-promoting rhizobacteria (PGPR), could be used in plant adaptation. These PGPR escape water scarcity conditions and relates to plants by modulating several microRNAs in plant stress responses. The present study relates the beneficial role of PGPR ( Pseudomonas putida- RA) responsive Car -miR166 of chickpea in drought mitigation with phytohormonal crosstalk in transgenic Arabidopsis lines. The transgenic lines showed an increased percentage of seed germination in comparison to treated control plants with highest germination rate in T2 (90%) and highest root length was observed in drought treated inoculated T1 lines (29%) under 300 mM of mannitol. The various physiological parameters including photosynthesis rate, transpiration rate, water-use efficiency and stomatal conductance were also better along with lower electrolyte leakage and higher relative water content in treated transgenic lines under inoculated conditions. The biochemical parameters including enzymatic and non-enzymatic antioxidants were improved in transgenic lines with less membrane damage and the highest accumulation of proline in T2 lines under RA inoculation and drought stress in comparison to treated control. The miR166 in drought-treated inoculated plants was highly upregulated (≥ 4) log2 fold change in T3 whereas the target was highly downregulated (≥ -2) log2 fold change in T2. Overall, our results concluded that RA-responsive Car -miR166 plays beneficial stress-mitigating roles under drought in transgenic plants, suggesting its crucial role in crop enhancement in response to PGPR.