Comparative transcriptome profiling reveals the defense pathways and mechanisms in the leaves and roots of blueberry to drought stress

Blueberry is an important horticultural plant that is very susceptible to drought. However, the molecular regulation mechanisms of blueberry tolerance to drought remain elusive. In this study, the transcriptome profile of blueberry by RNA-seq under different degrees of drought treatment were conducted and drought-related genes and pathways were screened using weighted gene co-expression network analysis (WGCNA) and Venn analysis. Interestingly, the leaves and roots of blueberry exhibited different expression patterns under drought treatment and differentially expressed genes (DEGs), GO terms and KEGG pathways were more enriched in leaves than in roots. The majority of DEGs were associated with signal transduction, transcriptional regulation, and metabolism. Eight key pathways and eight DEGs were shared both in leaves and roots. Notably, the pathway with the most core genes in leaves is the plant hormone signal transduction pathway, and in roots are the MAPK signaling pathway, reactive oxygen species metabolism and the key genes such as VcXTH3, VcPP2C51, and VcPNC1 were identified. For transcription factors, VcABR1, VcABF2, VcMYB108 and VcMYB93 are likely involved in drought response. In the metabolism category, VcCYP75A1 was likely involved in anthocyanin biosynthesis, and VcPNC1 in the monoterpenoid biosynthesis pathway. The eight DEGs markedly induced under drought exhibited differential expression in leaves and roots. Correspondingly, physiological assays showed that POD activity, ABA content, and anthocyanin biosynthesis in leaves and roots were significantly increased. Collectively, our study revealed the synergistic and distinct defense pathways and mechanisms in leaves and roots of blueberry and explored the potential regulatory network in blueberry response to drought stress.