MicroRNAs in the response of non-heading Chinese cabbage to Hyaloperonospora parasitica (downy mildew) infection

Abstract

Background MicroRNAs (miRNAs) are a subset of endogenous small non-coding ~21 nucleotide RNAs, which are playing important roles in development, abiotic stress, and pathogen responses. Downy mildew, caused by Hyaloperonospora parasitica , is a severe fungal disease in non-heading Chinese cabbage ( Brassica rapa ssp. chinensis ). However, miRNAs and their targets involved in the response of non-heading Chinese cabbage to downy mildew were still unclear. Results Here, fifteen small RNA libraries were generated from non-heading Chinese cabbage leaves at different time points after H. parasitica inoculation. By deep sequencing, we identified 197 known miRNAs and 112 novel miRNAs. According to data analysis, 8 known miRNAs and 8 novel miRNAs were found to be responsive to downy mildew infection in non-heading Chinese cabbage. Expression levels of 12 predicted miRNAs target genes were determined by reverse transcription-quantitative polymerase chain reaction (qRT-PCR). In this study, we proposed a regulatory network showing that non-heading Chinese cabbage defense response to downy mildew by repressing cell wall pectin, lipid and cellulose catabolic process ( PME12 , PME17 , PLAIVA and GDPDL4 ) and callose deposition ( CYP79B2 ), repressing indole glucosinolate metabolic process ( CYP81F3 ), repressing respiratory burst ( PUB24 ), repressing programmed cell death ( CRK5 ), and inducing defense related gene expression ( ROS1 , LECRK-VII.2 , BAK7 and WRKY48 ). Conclusions This research identified miRNAs associated with downy mildew infection in non-heading Chinese cabbage. Target genes and network analysis contributed to understanding the interaction between plant and pathogen.