Abstract
MicroRNAs (miRNAs), a type of short (21–23 nucleotides), non-coding RNA molecule, mediate repressive gene regulation through RNA silencing at the post-transcriptional level, and play an important role in defense and response to abiotic and biotic stresses. In the present study, Affymetrix® miRNA Array, real-time quantitative PCR (qPCR) for miRNAs and their targets, and miRNA promoter analysis were used to validate the gene expression patterns of miRNAs in Populus trichocarpa plantlets induced with the poplar stem canker pathogen, Botryosphaeria dothidea. Twelve miRNAs (miR156, miR159, miR160, miR164, miR166, miR168, miR172, miR319, miR398, miR408, miR1448, and miR1450) were upregulated in the stem bark of P. trichocarpa, but no downregulated miRNAs were found. Based on analysis of the miRNAs and their targets, a potential co-regulatory network was developed to describe post-transcriptional regulation in the pathological development of poplar stem canker. There was highly complex cross-talk between diverse miRNA pathway responses to biotic and abiotic stresses. The results suggest that miR156 is probably an integral component of the miRNA response to all environmental stresses in plants. Cis-regulatory elements were binding sites for the transcription factors (TFs) on DNA. Promoter analysis revealed that TC-rich repeats and a W1-box motif were both tightly related disease response motifs in Populus. Promoter analysis and target analysis of miRNAs also revealed that some TFs regulate their activation/repression. Furthermore, a feedback regulatory network in the pathological development of poplar stem canker is provided. The results confirm that miRNA pathways regulate gene expression during the pathological development of plant disease, and provide new insights into understanding the onset and development of poplar stem canker.
Highlights
MicroRNAs are short (21–23 nucleotides) noncoding RNA molecules that mediate repressive gene regulation through RNA silencing at the post-transcriptional level in plants and animals [1]
In ours previous inoculation study, we found that the symptoms of canker disease appeared on the bark of P. trichocarpa at 10–14 days after inoculation by canker pathogen, B.dothidea strain CZ060
A large number of poplar miRNAs (193 of 234 miRNAs) were not differentially regulated or response to pathogen inoculation at these three time points. These results provided the first experimental evidence that a set of miRNAs are involved in the regulation of gene expression in the pathological development of poplar canker disease
Summary
MicroRNAs (miRNAs) are short (21–23 nucleotides) noncoding RNA molecules that mediate repressive gene regulation through RNA silencing at the post-transcriptional level in plants and animals [1]. It was reported that the expression level of tomato (Solanum lycopersicum) miR482 suppressed at 4 h after inoculation by bacterial (Pto DC3000 and hrcC) or viral pathogens, while the expression level of their target genes (Nucleotide Binding Site–Leucine-Rich Repeats proteins coding zgenes, NBS-LRR protein coding genes) increased [16]. These studies suggested some miRNAs that target disease resistence genes could play an important role in the defense against pathogen attack
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