Target-mimicry based miRNA167-diminution ameliorates cotton somatic embryogenesis via transcriptional biases of auxin signaling associated miRNAs and genes

In vitro regeneration of cotton seems to be highly genotype dependent and typically ensues through the extraordinarily complex mechanism of somatic embryogenesis (SE). During the acquisition of embryogenic potential by the somatic cells, 21-24 nucleotides long regulatory microRNAs, especially miRNA167 plays a crucial role in the regulation of auxin signaling by degrading or inhibiting target mRNA molecules. To reveal the mechanism of regulation of target genes and the influence of key SE-associated miRNAs on the acquisition of embryogenic potential by the somatic cells, we employed target-mimicry approach of miR167 diminution for loss-of-function analysis encompassing callogenesis and in vitro embryogenesis stages of a fully-regenerating line of Coker 310 cultivar. Results demonstrated that miR167-diminution led to enhanced callogenesis and increased production of somatic embryos in the mimic-transformed events. In the MIM167-transformed calli, ARF6/ARF8, auxin-responsive GH3, auxin transporter Aux1, and auxin influx/efflux carrier LAX3, PIN1 and PIN2 genes showed a greater shift than control/non-transformed events, and suggested that miR167 diminution led to enhanced cellular auxin-signaling. Moreover, auxin-signaling associated microRNAs-miR160, miR393, miR166, miR156 and miR157 were differentially expressed in MIM167 mimic events indicating that diminution of miR167 also influenced the expression of these miRNAs. Evidently, miR166-LEC2 pair supplemented auxin signaling associated miR167-ARF6/ARF8 module that consequently may have resulted into substantial phenotypic transformations during embryonic transitions of cotton cultures. Key message Coordinated and fine-scale expression-network of auxin signaling-associated miRNAs and genes in miR167-target mimic transgenic calli of cotton, directed the incessant production of somatic embryos.