Small RNAs in Plants.- Role of microRNA miR319 in Plant Development.- The Roles of miR156 and miR172 in Phase Change Regulation.- Roles of miR156 and miR172 in Reproductive Development.- Trans-acting Small Interfering RNAs: Biogenesis, Mode of Action and Role in Plant Development.- Role of miRNAs in Seed Development.- Genetic and Molecular Approaches to Assess microRNA Function.- Functions of miRNAs in Rice.- microRNA Regulation of Symbiotic Nodule Development in Legumes.- Roles of miRNAs in Nutrient Signaling and Homeostasis.- Role of microRNAs in Plant Adaptation to Environmental Stresses.- Endogenous Small RNAs and Antibacterial Resistance in Plants.- Role of Virus-derived Small RNAs in Plant Antiviral Defense: Insights from DNA Viruses.