Extensive profiling of the expressions of tRNAs and tRNA-derived fragments(tRFs)reveals the complexities of tRNA and tRF populations in plants

Evidence is emerging that t RNA-derived fragments(t RFs)are regulatory molecules.Studies of t RFs in plants have been based on conventional small RNA sequencing,and focused on profiling of t RF-5 and t RF-3 species.A more comprehensive and quantitative analysis of the entire t RF population is highly necessary.Here,we employ t RNA-seq and YAMAT-seq,and develop a bioinformatics tool to comprehensively profile the expressions of t RNAs and t RFs in plants.We show that in Arabidopsis,approximately half of t RNA genes are extremely weakly expressed,accounting for only 1%of total t RNA abundance,while~12%of t RNA genes contribute to~80%of t RNA abundance.Our t RNA sequencings in various plants reveal that t RNA expression profiles exhibit a cross-species conserved pattern.By characterizing the composition of a highly heterogeneous t RF population,we show that t RNA halves and previously unnoticed 10–16-nt tiny t RFs represent substantial portions.The highly accumulated 13-nt and 16-nt tiny t RFs in Arabidopsis indicate that tiny t RFs are not random t RNA degradation products.Finally,we provide a user-friendly database for displaying the dynamic spatiotemporal expressions of t RNAs and t RFs in the model plants Arabidopsis and rice.