MsmiR156 Promotes Root Development and Nitrogen Fixation Activity in Alfalfa

MicroRNA156 (miR156) regulates a network of genes that affect plant growth and development. Previous studies have generated alfalfa (Medicago sativa) plants that overexpress homologous miR156 (MsmiR156OE), which exhibited increased vegetative yield, delayed flowering, and longer roots. A team of scientists from the Agriculture and Agri-Food Canada led by Banyar Aung aimed to explain the effect of miR156 on the root system, including effect on nodulation and nitrogen fixation.

The team found that MsmiR156 overexpression increases root regeneration capacity in alfalfa, but with little effect on root biomass at the early stages of root development. MsmiR156 also promotes nitrogen fixation activity by upregulating expression of nitrogenase-related genes such as FixK, NifA, and RpoH in roots inoculated with Sinorrhizobium meliloti.

Further analysis of MsmiR156OE alfalfa roots identified differentially expressed genes belonging to different functional categories, including plant cell wall organization and response to water stress. Analysis also revealed the effects of miR156 on genes involved in nodulation, root development, and phytohormone biosynthesis.

These findings suggest that miR156 regulates root development and nitrogen fixation activity and thus it is vital in the improvement of alfalfa and other crops.

For more on this study, read the article in Transgenic Research.