| Wheat is a worldwide food crop,and disease control is one of the main measures to ensure stable production.Fusarium head blight（FHB）is a fungal disease caused by Fusarium graminearum,which can invade the roots,stem bases,and spikes of wheat,resulting in root rot,stem base rot,spike wilt,and accumulation of a large amount of deoxynivalenol in the grain.As a result,wheat yield is greatly reduced,and excessive grain toxin seriously threatens food safety.However,due to various factors,such as difficulty in phenotypic evaluation,sensitivity to the environment and complexity of the wheat genome,the cloning of major genes for FHB resistance has been slow and the regulatory mechanism is still unclear.tRNA-derived fragments（tRFs）were first discovered in animals,which are small RNA molecules formed from tRNA cleavage by endonuclease.The length of tRFs is similar to microRNA.Similar to miRNA in function,it can form a complex with AGO protein,recognize the matching target gene,and then splice mRNA or inhibit its translation.A large amount of tRFs has been identified in Arabidopsis,rice,soybean,maize,alfalfa,sorghum,grape and other plants,but not in wheat.In this study,the high-throughput sequencing method was used to analyze the tRFs of the FHB highly resistant wheat cultivar Sumai3（SM3）,and the moderately susceptible wheat cultivar Chinese Spring（CS）.The results show that the total amount of tRFs was comparable to that of miRNA.A total of 1249 tRFs were found,of which 15 tRFs were specifically accumulated in CS and 12 were specifically accumulated in SM.Compared with controls,39 tRFs were significantly up-regulated and only 9 tRFs were significantly down-regulated in both wheat cultivars after F.graminearum infection.Fusarium graminearum infection significantly induced the expression of tRF-Glu,tRF-Lys,tRF-Thr,and tRF-Met.We also predicted the target genes of all identified tRFs,and preliminarily identified the tRFs target genes via transcriptome sequencing,and performed RACE verification on some tRFs target genes.The results showed that most of the tRFs were up-regulated after Fusarium graminearum invasion,while the expression of the corresponding target genes showed a down-regulation trend.GO and KEGG analysis indicated that the target genes were involved in disease resistance response and maintenance of normal cellular metabolic activities.Transcriptome and qRT-PCR validation revealed that members of the RNaseT2 family of nucleases that form tRFs were significantly induced after F.graminearum infection,indicating that RNaseT2 may be involved in tRFs formation after wheat infection with F.graminearum.The identification and analysis of tRFs can provide a new idea for the analysis of the pathogenesis of FHB. |
