MicroRNA156 improves drought stress tolerance in alfalfa (Medicago sativa) by silencing SPL13.

Alfalfa (Medicago sativa) is an important forage crop that is often grown in areas that frequently experience drought and water shortage. MicroRNA156 (miR156) is an emerging tool for improving various traits in plants. We tested the role of miR156d in drought response of alfalfa, and observed a significant improvement in drought tolerance of miR156 overexpression (miR156OE) alfalfa genotypes compared to the wild type control (WT). In addition to higher survival and reduced water loss, miR156OE genotypes also maintained higher stomatal conductance compared to WT during drought stress. Furthermore, we observed an enhanced accumulation of compatible solute (proline) and increased levels of abscisic acid (ABA) and antioxidants in miR156OE genotypes. Similarly, alfalfa plants with reduced expression of miR156-targeted SPL13 showed reduced water loss and enhanced stomatal conductance, chlorophyll content and photosynthetic assimilation. Several genes known to be involved in drought tolerance were differentially expressed in leaf and root of miR156 overexpression plants. Taken together, our findings reveal that miR156 improves drought tolerance in alfalfa at least partially by silencing SPL13.