Transcriptomic profiling and discovery of key genes involved in adventitious root formation from green cuttings of highbush blueberry (Vaccinium corymbosum L.)
Abstract Background Propagation of cuttings was mostly used in various plant species including blueberry, the special root characteristics of blueberry usually resulted in a difficulty in adventitious root (AR) formation. The AR formation was influenced by various factors, of which auxin was considered to play a center role, however little is known of the related regulative mechanisms. In this study, transcriptome analysis using RNA_seq from the stem of green cuttings of southern highbush blueberry 'Biloxi' was performed to discover candidate genes associated with AR formation.Results Rooting phenotypes, especially rooting rate, was significantly promoted by exogenous auxin IBA application. The adventitious root primordium initiation (rpi) began to be formed at 14 day (d) after cutting, developed into root primordium (rp) at 21d, finally the rp further developed to mature AR at 28d. Higher IAA and lower ABA and zeatin might facilitate the AR formation and development. A time series transcriptome analysis indentified 14970 differentially expressed genes (DEGs) during AR formation, of which there were 7467 up-regulated and 7503 down-regulated genes, respectively. Of these, about 35 candidate DEGs involved in auxin-induced pathway and AR formation were further identified, including 10 auxin respective genes ARFs and SAURs , 13 transcription factors LOB domain-containing protein ( LBD s), 6 auxin transporter AUX22 , LAX3/5 and PIN-like 6s ( PIL6s ) and 6 rooting-associated genes root meristem growth factor 9 ( RGF9 ), lateral root primordium 1 ( LRP1s ), dormancy-associated protein homolog 3 ( DRMH3 ). All these identified DEGs were highly up-regulated in certain AR developed stage, indicating their potential roles in blueberry AR formation.Conclusions The transcriptome profiling indicated candidate genes or major regulative factors that influence adventitious root formation in blueberry, and provided a comprehensive understanding of rooting mechanism of the auxin-induced AR formation from blueberry green cuttings.