Characterization of the Rosa roxburghii Tratt transcriptome and analysis of MYB genes.

Rosa roxburghii Tratt (Rosaceae) has a fruit that is flavorful, economically valuable, and highly nutritious, providing numerous health benefits. Myeloblastosis (MYB) proteins play key roles in the development and fruit quality of R. roxburghii. However, there is little available genomic and transcriptomic information for R. roxburghii. Here, a normalized cDNA library was constructed from five tissues, including the stem, leaf, flower, young fruit, and mature fruit, using the Illumina HiSeq 3000 platform. De novo assembly was performed, and 470.66 million clean reads were obtained. In total, 63,727 unigenes, with an average GC content of 42.08%, were discovered, 60,406 of which were annotated. In addition, 9,354 unigenes were assigned to Gene Ontology categories, and 20,202 unigenes were assigned to 25 Eukaryotic Ortholog Groups. Additionally, 19,508 unigenes were classified into 140 pathways of the Kyoto Encyclopedia of Genes and Genomes database. Based on the transcriptome, 163 unigenes associated with MYBs were detected. Among these genes, 75 genes were significantly expressed in the various tissues, including 10 R1 MYB, 42 R2R3 MYB, one R1R2R3 MYB, three R4 MYB and 19 atypical MYB-like proteins. The expression levels of the 12 MYB genes randomly selected for quantitative real-time PCR analysis corroborated the RNA sequencing results. A total of 37,545 microsatellites were detected, with an average expressed sequence tag-simple sequence repeat frequency of 0.59 (37,545/63,727). This transcriptome data improves our understanding of the role of MYB in R. roxburghii and will be valuable for identifying genes of interest.