Role of microRNAs During Flower and Storage Root Development in Sweet Potato.

Sweet potato ( Ipomoea batatas) is one of the major food and vegetable crops around the world. Sweet potato produces two types of roots: storage roots and fibrous roots. The tuberous root is a modified lateral root that functions as a storage organ, and is the portion of the plant consumed by humans. However, the molecular mechanisms controlling transformation of lateral roots to storage roots are still unclear. In this study, we systematically investigated the potential role of 16 conserved microRNAs (miRNAs) in floral root development. miRNAs are an extensive class of small regulatory RNAs controlling almost all biological and metabolic process in plants. Our results show that some miRNAs are expressed in an organ-dependent manner. For example, the expression level of miR156 and miR162 was significantly lower in storage roots than in leaves and fibrous roots. This suggests that miRNAs may play a role during storage root initiation and development. The expression of miR167 is higher in stamens than that in other tissues tested, indicating that miR167 is crucial to stamen development. miR398-a stress-responsive miRNA-may be involved in fibrous root and storage root development. Additionally, three miRNAs, miR160, miR164 and miR166, also appear to be important in fibrous root and storage root development. [ABSTRACT FROM AUTHOR]