Developmentally-controlled generation of tRNA halves facilitates translational repression during sexual reproduction

The role of transfer RNAs (tRNAs) as mediators between the genetic code and protein synthesis is well established. In parallel, tRNAs can generate different types of functional small RNAs (sRNAs) that accumulate during stress and certain developmental processes across diverse organisms. Interestingly, this class of sRNAs (termed tRNA-derived sRNAs, tsRNAs) accumulate in the male gamete of mammals, insects, and plants but their role in these reproductive cells is unclear. Here, we determine the molecular pathway of tsRNA biogenesis in the plant male gamete-containing structure (the pollen grain) and identify their role in mediating the characteristic translational repression taking place in this tissue. Our data demonstrates that male-accumulating tsRNAs are generated by a cell-controlled pathway to aid in mediating reproductive translational repression and that their accumulation is key to ensuring the proper function of the pollen grain.