A 5′tRNA-Ala-derived small RNA regulates anti-fungal defense in plants

Apart from their primordial role in protein synthesis,t RNAs can be cleaved to produce t RNA-derived small RNAs(ts RNAs).The biological functions of ts RNAs in plants remain largely unknown.In this study,we developed Rtc B ligation-based small RNA(s RNA)sequencing,a method that captures and distinguishes between 3′-2′,3′-cyclic-phosphate(c P)/phosphate(P)-terminated s RNAs and 3′-OH-terminated s RNAs,and profiled 5′ts RNAs and 5′t RNA halves in Arabidopsis thaliana.We found that Arabidopsis 5′ts RNAs and 5′t RNA halves predominantly contain a c P at the 3′end and require S-like RNase 1(RNS1)and RNS3 for their production.One of the most abundant 5′ts RNAs,5′ts R-Ala,by associating with AGO1,negatively regulates Cytochrome P45071 A13(CYP71 A13)expression and camalexin biosynthesis to repress anti-fungal defense.Interestingly,5′ts R-Ala is downregulated upon fungal infection.Our study provides a global view of 5′ts RNAs and 5′t RNA halves in Arabidopsis and unravels an important role of a 5′ts RNA in regulating anti-fungal defense.