Abstract
Small RNAs are important regulators for a variety of biological processes, including leaf development, flowering-time, embryogenesis and defense responses. miR163 is a non-conserved miRNA and its locus has evolved recently through inverted duplication of its target genes to which they belong to the SABATH family of related small-molecule methyltransferases (MTs). In Arabidopsis thaliana, previous study demonstrated that miR163 accumulation was induced by alamethicin treatment, suggesting its roles in defense response pathways. Enhanced resistance against Pseudomonas syringae pv. tomato (Pst) was observed in the mir163 mutant, whereas transgenic lines overexpressing miR163 showed increase sensitivity to Pst, suggesting that miR163 is a negative regulator of defense response. Elevated level of miR163 and its targets in A. thaliana were observed upon Pst treatment, suggesting a modulating relationship between miR163 and its targets. In addition, miR163 and histone deacetylase were found to act cooperatively in mediating defense against Pst. Transgenic plants overexpressing miR163-resistant targets suggested their different contributions in defense. Results from this study revealed that the stress-inducible miR163 and its targets act in concert to modulate defense responses against bacterial pathogen in A. thaliana.
Highlights
MiR163 is an Arabidopsis-specific miRNA that appears relatively recent in evolutionary time[10]
We found that miR163 accumulation was affected in the hda[19] mutant and it is likely that miR163 and histone deacetylase 19 (HDA19) act cooperatively in maintaining the basal defense
It has been showed that miR163 and its targets are potentially involved in plant defense[19]
Summary
Small RNAs are important regulators for a variety of biological processes, including leaf development, flowering-time, embryogenesis and defense responses. miR163 is a non-conserved miRNA and its locus has evolved recently through inverted duplication of its target genes to which they belong to the SABATH family of related small-molecule methyltransferases (MTs). In Arabidopsis thaliana, previous study demonstrated that miR163 accumulation was induced by alamethicin treatment, suggesting its roles in defense response pathways. Results from this study revealed that the stress-inducible miR163 and its targets act in concert to modulate defense responses against bacterial pathogen in A. thaliana. Different from most typical 21-nt plant miRNAs, miR163 is a non-conserved 24-nt miRNA and its locus has evolved recently by inverted duplication of its target gene that belongs to the SABATH family of small molecules methyltransferases and the MIR163 locus is located close to a cluster of three SABATH genes on chromosome 111,14,15. Results supported that miR163 is a negative regulator of basal defense against bacterial pathogen Both miR163 and its targets were induced in response to P. syringae infection, suggesting miR163 acts to modulate the target genes expression under stress. Our findings provide additional insights to the emergence and co-evolution of miRNA and its targets in modulating defense against bacterial pathogens
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