Flowering time regulation by the miRNA156 in the beet (Beta vulgaris ssp. maritima)

Successful reproduction of the plants is considered as a critical challenge in meeting the nutritional needs of the growing world population. A major significant change in the plant's life cycle is the transition from vegetative to reproductive phase. The flowering and bolting processes are influenced by several genetic and physiological factors. Molecular and genetic studies have identified key factors in age-dependent gene regulatory pathways such as miR172-miR156-SPLs module in phase transition in plants. Unlike in model plants, the role of miR172-miR156-SPLs like regulatory networks remains unexplored in crops such as Beta vulgaris. In the present study, for the first time, miR156 from Beta vulgaris was identified and characterized. miR156 gene from Beta vulgaris was cloned and ectopically overexpressed under the control of strong 35S promoter in sugar beet explants. Subsequently, transcript levels of the miR156 and its known targets (SPL4 and SPL9) were quantified in the transgenic and control plants. Consistent with reported role of mir156 in downregulation of SPL4 and SPL9, miR156 overexpression plants exhibited delayed flowering and atypical rooting pattern indicative of abnormal root development and poor root foraging performance. Altogether, our results suggest that Beta vulgaris miR156 modulate phase transition by acting as negative regulator of SPL4 and SPL9.