Gibberellin induces rapid regeneration of juveniles from the Sargassum fusiforme holdfasts

Sexual reproduction of economically valuable Sargassum fusiforme can lead to genetic drift of useful strains and reduce their economic benefits. The number of juveniles from S. fusiforme holdfasts in the natural state is very small. Gibberellin (GA) may play an important role in S. fusiforme holdfast regeneration. This study further explored the application of GA to promote the rapid juvenile regeneration from S. fusiforme holdfast and explored its mechanism. Exogenous addition of 1.5 mg⸱L⁻¹ GA significantly shortened the regeneration time of S. fusiforme holdfast and induced more juvenile regeneration. KEGG analysis showed that the differential genes induced by GA treatment were mainly enriched in the ribosomal pathway, carbon assimilation metabolism, and oxidative phosphorylation pathway. GA not only enhanced the photosynthetic capacity of holdfast, but also upregulated the Ca²⁺ signaling pathway by enhancing CaM gene expression, up-regulating the expressions of Ran gene associated with cell cycle regulation, MDH, aconite hydratase, GAPDH, FBA, and G6PDH associated with carbon assimilation metabolism. In addition, it also upregulated the expression of F-type H⁺-transport ATPase subunit a, promoting the accumulation of nutrients in holdfasts and the supply of energy required for the regeneration, thus promoting their growth. Thus, exogenous induction of holdfasts regeneration with 1.5 mg⸱L⁻¹ GA₃ can be used to solve the problem of the scarce number of juveniles from holdfasts and obtain more stable genetically dominant strains for more and faster regeneration of juveniles, to improve the actual production efficiency.