Transcriptome-Wide Characterization of Novel and Heat-Stress-Responsive microRNAs in Radish (Raphanus Sativus L.) Using Next-Generation Sequencing

Abstract

microRNAs (miRNAs) are a class of single-stranded endogenous non-coding RNAs that play critical roles in plant growth, development, and environmental stress responses. Temperature is one of the major physical parameters disturbing cellular homeostasis and causing leaf etiolation in plants. Previous studies have reported that several conserved and novel miRNAs were responsive to heat stress in plants. However, the characterization of miRNAs responsive to heat stress in radish remains poorly understood. To better understand miRNAs and their target genes under heat stress, two small RNA libraries were constructed from heat-treated (Heat24) and heat-untreated (CK) radish roots. Using Solexa system, totally, 26 known and 19 novel miRNAs were identified as differentially expressed under heat stress. Expression patterns of a set of heat-responsive miRNAs were validated by quantitative real-time PCR (qRT-PCR). Furthermore, 422 sliced targets for 25 known miRNAs were identified by degradome sequencing technology, and most of the identified targets are involved in multiple biological processes including transcriptional regulation and response to biotic and abiotic stresses. Moreover, some miRNAs and their corresponding targets, which are related to the accumulation of heat stress transcription factors and heat shock proteins, played important roles in thermo-tolerance in radish. These findings could enhance the understanding of molecular mechanisms underlying miRNAs and their targets in regulating plant responses to heat stress.