Transcriptome analysis revealed the regulatory mechanism of DIMBOA affecting early somatic embryogenesis in Dimocarpus longan Lour.

Dimocarpus longan Lour. is an evergreen tree of the genus Longan in the Sapindaceae family, native to tropical and subtropical regions. Longan embryonic development is closely linked to fruit set and fruit quality. An in-depth study of the mechanism of longan embryonic development could therefore contribute to the development of the longan industry. DIMBOA was closely linked to auxin biosynthesis and signal regulation. Auxin is one of the important hormones for inducing somatic embryogenesis (SE) in plants. Previous studies have known that DIMBOA promotes morphogenesis in early somatic embryogenesis of longan, but the specific regulatory mechanism has not yet been clarified. To elucidate the molecular mechanism by which DIMBOA affects early somatic embryogenesis in longan, we chose longan embryogenic cultures grown under 0 mg/L DIMBOA as the control group (CK), and longan embryogenic cultures grown under 0.1 mg/L DIMBOA as the treatment group (D) to be analysed by transcriptomic sequencing. A total of 478 differentially expressed genes (DEGs) are detected in CK vs D, of which 193 are up-regulated and 285 are down-regulated. These DEGs are significantly enriched in the biosynthetic and metabolic functions of various substances such as vitamin B6 biosynthesis, phenylpropanoid pathways and carbohydrate metabolism. DIMBOA regulates SE processes in longan via TFs, including MYB, ZF, bHLH, LBD, NAC and WRKY, etc. After DIMBOA treatment, the expression of most of the key genes for IAA synthesis was significantly down-regulated, VB6 content was significantly reduced and H2O2 content was significantly increased. Therefore, it is suggested that DIMBOA directly or indirectly affect the H2O2 content through the VB6 metabolic pathway, thereby regulating the endogenous IAA level to regulate the early SE morphogenesis of longan.