Transcriptomic response of apple (Malus × domestica Borkh. cv. Húsvéti rozmaring) shoot explants to in vitro cultivation on media containing thidiazuron or 6-benzylaminopurine riboside

Abstract One of the most critical factors in maintaining healthy in vitro axillary apple shoot cultures is the cytokinin content of the medium. The effects of two cytokinins applied in the medium, thidiazuron and 6-benzylaminopurine riboside, each applied in a quantity of 4.5 µM, were studied on mRNA transcription of in vitro apple shoots. Transcriptomic response of in vitro apple shoots was investigated at two time points; at 48 h and 4 weeks (at the end of the subculture) after the cytokinin application by mRNA-seq, bioinformatics analysis, GO annotation and KEGG mapping. This study revealed that different expression intensities of DEGs were related to TF families (mainly WRKY, MYB, AP2/ERF, bHLH) associated with plant growth and development, in addition to enzymes involved in genetic and environmental information processing, cell motility, the zeatin biosynthesis, the tryptophan metabolism, the phenylpropanoid biosynthesis, and cutin, suberin, and wax biosynthesis. A putative roadmap based on changes in gene expression intensity that may be in association with various in vitro apple shoot development and growth disorders caused by different cytokinin supplies was conceived.