Sorghum-encoded microRNAs: current status and future prospects

Sorghum (Sorghum bicolor (L.) Moench) is an annual or short-term perennial plant belonging to the economically important family Poaceae. Sorghum, a C4 crop, has multiple uses like food, fodder, forage, and also as a biofuel feedstock. With an ability to thrive under harsh environmental conditions and adaptability to diverse climates and soils, sorghum has a long history of cultivation in the semi-arid tropics of Africa, Asia, and Latin America. Gene regulation plays an important role in adaptability to adverse environmental conditions. MicroRNAs (miRNAs) are one of the classes of small non-coding RNAs that have emerged as a key regulators of gene expression. These small RNAs are profoundly present in all higher eukaryotes including plants. These are involved in regulating the intrinsic normal growth of cells and the development of organisms as well as in maintaining the integrity of genomes. In plants, miRNAs have been functionally implicated in abiotic stress tolerance, flower development, root development, grain size determination, yield, and immune responses. Several miRNAs have been reported in sorghum, and the potential functions of some miRNAs have been characterized. Here, in this review, an overview of sorghum-encoded miRNAs is provided. The potential known and putative functions of these miRNAs are critically discussed. In addition, the possible methods for employing miRNAs as a tool for sorghum improvement are also suggested. The present review will help us to understand the miRNA functions in sorghum and underlying regulatory gene networks which have applications to design effective methods to achieve desired traits.