AGL61/80 regulates BGAL9, which participates in early somatic embryogenesis and increases longan resistance to heat stress

Abstract

β-galactosidase (BGAL) is a glycosyl hydrolase that participates in cell wall modification, playing an essential role in plant growth, development and environmental stress adaptation. However, the function of BGALs in longan remains unclear. In this study, a total of 20 BGAL genes were identified from the longan (Dimocarpus longan Lour.) genome, which were distributed to eight chromosomes. Transcript profiles revealed that the majority of 11 detected DlBGAL genes were highly expressed in the embryogenic callus (EC) (four) and globular embryos (GE) (six), and responsive to heat stress. Combined with RNA-seq, ATAC-seq, and ChIP-seq results, most DlBGAL genes differentially expressed during early somatic embryogenesis (SE) were related with chromatin accessibility and high levels of H3K4me1. DlBGAL9 was selected for further analysis. Dual-luciferase assays and transient transformation indicated that the transcription factor (TF) DlAGL61 and DlAGL80 might bind to the DlBGAL9 promoters to activate DlBGAL9 transcription. Overexpression of DlBGAL9 and TF DlAGL80 induces longan hairy roots β-GAL activity and thickening of cell walls. The expression levels of DlBGAL9 and TF DlAGL80 in longan hairy roots were significantly increased under heat stress, and ROS scavengers related genes were significantly upregulated in overexpressing DlBGAL9 and TF DlAGL80 hairy roots. This study proposes the significance of the regulatory network composed of DlBGAL9 and TF DlAGL80 in regulating the early longan SE and heat stress response.

Keywords

• d. longan
• β-galactosidase (bgal)
• transcriptional factor
• somatic embryogenesis
• heat stress