MdMYB4 enhances apple callus salt tolerance by increasing <Emphasis Type="Italic">MdNHX1</Emphasis> expression levels

Here, we performed comparative miRNA profiling in wild type and early flowering transgenic Chrysanthemum morifolium with constitutive expression of APETALA1 (AP1)-like gene, HAM92 (Helianthus annuus). Six sRNA libraries constructed from leaves and shoot apexes after the short day photoperiod initiation, as well as from opened inflorescence after anthesis were sequenced and analyzed. A total of 324 members (163 families) of putative conserved miRNAs and 30 candidate novel miRNAs specific for C. morifolium (cmo-miRNAs) were identified. Bioinformatic analysis revealed 427 and 138 potential mRNA targets for conserved and novel cmo-miRNAs, respectively. These genes were described in Gene Ontology terms and found to be implicated in a broad range of signaling pathways. Plant- and tissue-specific expression of 9 highly conserved cmo-miRNAs was compared between wild type and transgenic chrysanthemum lines with ectopic expression of AP1-like genes HAM92 and CDM111 (C. morifolium), using RT-qPCR and cmo-miR162a as a reference miRNA. The results of our study provide a framework for further investigation of miRNA evolution and functions in higher plants, as well as their roles in flowering control.