The multifaceted role of gibberellins in somatic embryogenesis: from in vitro culture to molecular networks
Gibberellins (GAs) are central regulators of plant growth and development, yet their involvement in somatic embryogenesis (SE) has received limited attention and often produces contradictory results. This review critically examines the current knowledge on the role of GAs in SE by integrating evidence from physiological, molecular, and developmental studies across a wide range of plant species. Available data indicate that exogenous GAs and GA biosynthesis inhibitors can either promote or inhibit the induction, progression, and conversion of somatic embryos, depending on the species, genotype, explant origin, developmental stage, and culture conditions. These opposing effects underscore that exogenous responses are tightly linked to endogenous GA homeostasis. Particular attention is paid to GA metabolism and signaling genes, whose expression patterns during SE reveal substantial interspecific and genotypic variation. Endogenous GA profiles reveal that both high and low levels of bioactive GAs correlate with SE induction across different systems, suggesting that endogenous GA levels may be a key determinant of embryogenic competence and may underlie major differences in regeneration capacity among species and genotypes. Furthermore, GAs function within a broader regulatory network through extensive crosstalk with other hormones (auxins, abscisic acid, cytokinins, and ethylene), environmental factors (e.g., light and temperature) and interactions with major embryogenesis-related transcription factors such as LEC1, LEC2, FUS3, ABI3, AGL15, AGL18, and BBM. These interactions position GAs as dynamic components of a multilayered hormonal and transcriptional framework that controls the switch from somatic to embryogenic development. Integrative approaches—including hormone profiling, gene expression analysis, functional genetics, and developmental studies—are essential to elucidate the precise function of GAs in SE and thereby improve protocols for plant regeneration.