# Transcriptome Analysis Revealed the Regulatory Mechanism of DIMBOA Affecting Early Somatic Embryogenesis in Dimocarpus longan Lour

## TL;DR

This study explores how DIMBOA influences early embryogenesis in longan trees by analyzing gene expression changes and metabolic pathways.

## Contribution

The study identifies specific genes and metabolic pathways regulated by DIMBOA during early somatic embryogenesis in longan.

## Key findings

- DIMBOA treatment alters 478 genes, with significant changes in vitamin B6, phenylpropanoid, and carbohydrate metabolism pathways.
- DIMBOA affects somatic embryogenesis via transcription factors like MYB, ZF, and bHLH.
- DIMBOA reduces vitamin B6 content and increases H2O2, potentially modulating auxin levels to regulate embryogenesis.

## Abstract

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 related 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 is the principal compound representing benzoxazinoids (BXs), and is closely linked to auxin biosynthesis and signal transduction. Auxin is one of the crucial hormones for inducing somatic embryogenesis (SE) in plants. Previous research has shown that DIMBOA promotes morphogenesis in the 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 (the check, CK), and longan embryogenic cultures grown under 0.1 mg/L DIMBOA as the treatment group (D) to be analyzed by transcriptomic sequencing. A total of 478 differentially expressed genes (DEGs) are detected in check vs. D, of which 193 are upregulated and 285 are downregulated. These DEGs are significantly enriched in the biosynthetic and metabolic functions of various substances such as vitamin B6 (VB6) biosynthesis, phenylpropanoid pathways, and carbohydrate metabolism. DIMBOA affects SE processes in longan via TFs, including MYB, ZF, bHLH, LBD, NAC, WRKY, etc. After DIMBOA treatment, the expression of most of the key genes for IAA synthesis was significantly downregulated, VB6 content was significantly reduced, and H2O2 content was significantly increased. Therefore, it is suggested that DIMBOA directly or indirectly affects the H2O2 content through the VB6 metabolic pathway, thereby regulating the endogenous IAA level to modulate the early SE morphogenesis of longan.