Time-Course Transcriptome and Phytohormonal Analysis of Blue-Light-Induced Adventitious Root Development of Tea Cuttings (Camellia sinensis (L.) Kuntze)

C. sinensis is an economically important crop for tea production that experiences increasing demand and good export potential. Therefore, crops need to be expanded, and high-quality planting material is required. Vegetative propagation by cuttings is the prevalent method; therefore, this paper explored its optimization potential modeled on cultivar ‘Jiukengzao’. This study wanted to deeply explore blue-light-induced adventitious root formation and development of tea cuttings, so we conducted short-term (0 h, 8 h, and 16 h) and long-term (30 d, 60 d, and 90 d) time-course analyses on tea cutting seedlings. Short-term, full-length transcriptome analysis showed that the expression of genes related to plant hormone signal transduction and auxin transport was highest at 16 h. Sixteen hours of light was considered as suitable for adventitious root growth and development of tea cuttings. Long-term phytohormone analysis showed that the trend of indole-3-carboxylic acid (ICA) change was: 60 d > 90 d > 30 d. Long-term, full-length transcriptome analysis showed that the gene expression trends in K2, K5, K6, and K8 clusters were: 90 d > 60 d > 30 d, and the opposite was observed in K1, K4, and K11 clusters. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that most of the genes in these seven clusters are involved in “plant hormone signal transduction (ko04075)”. This includes auxin early responsive protein AUX/IAA, auxin response factor ARF, auxin-responsive protein SAUR, etc. In addition, genes related to auxin transport and synthesis were identified as PIN1, 3, 4, PILS2, 6, 7, flavin-containing monooxygenase YUC9, and YUC10, and the expression trend of these genes was mostly consistent with the change trend of ICA content. This study further explained the molecular mechanism of blue-light-induced adventitious root formation and development of tea cuttings. It is recommended that blue light can be used to promote the adventitious root growth and development of tea cuttings in practical production.