Recent hybridization and allopolyploidy reprogrammed Spartina microRNA expression under xenobiotic induced stress.

Xenobiotic detoxification is a common trait of all living organisms, necessary for developmental plasticity and stress tolerance. The gene set involved in this biological process is dubbed the xenome (i.e. involved in drug metabolism in mammals, degradation of allelochemicals and environmental pollutants by bacteria and plant communities). Recently, we found that allopolyploidy increased tolerance to xenobiotics (phenanthrene) in Spartina. To decipher the molecular mechanisms underlying this process, we examined how interspecific hybridization and genome doubling impact miRNAs expression under xenobiotic induced stress. In this work we used a deep sequencing approach, and analyzed the parental species S. alterniflora and S. maritima, their F1 hybrid S. x townsendii and the allopolyploid S. anglica under phenanthrene exposure. We found that hybridization and genome doubling reprogrammed a myriad of miRNAs under phenanthrene-induced stress. Hence, to identify the master miRNAs involved in phenanthrene tolerance, we performed experimental functional validation of phenanthrene-responsive Spar-miRNAs using Arabidopsis T-DNA mutant lines inserted in homologous MIR genes, 39 knock out T-DNA Arabidopsis mutants, tagged in the most conserved miRNAs genes in vascular plants were screened. Development of MIR159 and MIR156 mutants was significantly affected under phenanthrene-induced stress. Subsequently, we performed in planta experimental validation to confirm the interaction between these miRNAs and their targets. These analyses suggest that MIR159 and MIR156 regulatory modules were targeted to induce the xenome relaxation and impact developmental plasticity responses in phylogenetically distant species under xenobiotic-induced stress. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/875138v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@9f620borg.highwire.dtl.DTLVardef@1ddd2f5org.highwire.dtl.DTLVardef@4501f1org.highwire.dtl.DTLVardef@82962d_HPS_FORMAT_FIGEXP M_FIG Graphical abstract C_FIG