Rice foot rot disease caused by the pathogen Dickeya zeae (formerly known as Erwinia chrysanthemi pv. zeae), is a newly emerging damaging bacterial disease in China and the southeast of Asia, resulting in the loss of yield and grain quality. However, the genetic resistance mechanisms mediated by miRNAs to D. zeae are unclear in rice. In the present study, 652 miRNAs including osa-miR396f predicted to be involved in multiple defense responses to D. zeae were identified with RNA sequencing. A total of 79 differentially expressed miRNAs were detected under the criterion of normalized reads ≥10, including 51 known and 28 novel miRNAs. Degradome sequencing identified 799 targets predicted to be cleaved by 168 identified miRNAs. Among them, 29 differentially expressed miRNA and target pairs including miRNA396f-OsGRFs were identified by co-expression analysis. Overexpression of the osa-miR396f precursor in a susceptible rice variety showed enhanced resistance to D. zeae, coupled with significant accumulation of transcripts of osa-miR396f and reduction of its target the Growth-Regulating Factors (OsGRFs). Taken together, these findings suggest that miRNA and targets including miR396f-OsGRFs have a role in resisting the infections by bacteria D. zeae.

Plant long non-coding RNA (lncRNA) is a type of newly emerging epigenetic regulator playing a critical role in plant growth, development, and biotic stress responses. However, it is unknown whether lncRNAs are involved in resistance responses between rice and Dickeya zeae, a bacterial agent causing rice foot rot disease. In this study, RNA-seq was performed to uncover the co-expression regulating networks mediated by D. zeae responsive lncRNAs and their candidate target genes. Of the 4709 lncRNAs identified, 2518 and 2191 were up- and down-regulated in response to D. zeae infection, respectively. Expression changes of 17 selected lncRNAs and their predicted targets with a potential role in defense response were investigated by qPCR. The expression levels of five lncRNAs were up-regulated while their cognate candidate target genes were down-regulated upon D. zeae infection. In addition, several lncRNAs were predicted to be target mimics of osa-miR396 and osa-miR156. These results suggest that lncRNAs might play a role in response to D. zeae infection by regulating the transcript levels of their targets and miRNAs in rice.