Gibberellins play an essential role in late embryogenesis of Arabidopsis

Abstract

The plant hormone gibberellin plays key roles in almost all aspects of plant development, but its detailed function and underlying regulatory mechanism in embryo development are not yet clearly defined. Here, we illustrate an essential role of gibberellin in late embryogenesis of Arabidopsis. Bioactive gibberellins are highly biosynthesized during the late developmental stage of embryos. At that time, deficiency in gibberellin biosynthesis or signalling results in an abnormal embryo phenotype characterized by less-developed cotyledons and shortened embryo axis. In contrast, gibberellin overdose leads to a significantly larger size of mature embryo. We reveal that the gibberellin signalling repressor DELLA interact with LEAFY COTYLEDON1 (LEC1), the key regulator in late embryogenesis. Gibberellin triggers the degradation of DELLAs to relieve their repression of LEC1, thus promoting auxin accumulation to facilitate embryo development. Therefore, we uncover a space/time-specific role of gibberellin in regulating late embryogenesis through the gibberellin-DELLA-LEC1 signalling cascade, providing a novel mechanistic understanding of how phytohormones regulate embryogenesis.

Central role of the LEAFY COTYLEDON1 transcription factor in seed development

“…Consistent with this interpretation, trichome development is suppressed in plants overexpressing LEC1 (Lotan et al ; Huang et al ). Fourth, LEC1 regulates the expression of genes involved in embryo morphogenesis, including those encoding the transcription factors PHAVOLUTA and SCARECROW, and in auxin biosynthesis in Arabidopsis and soybean embryos early in seed development (Junker et al ; Pelletier et al ; Hu et al ). Finally, a striking indication of LEC1's role in embryo morphogenesis is its ability to induce somatic embryo development in vegetative tissues of several plant species (Lotan et al ; Lowe et al ; Yang and Zhang ; Ledwon and Gaj ; Guo et al ; Nic‐Can et al ; Orlowska et al ).…”

“…Recent findings provide insight into the mechanisms by which LEC1 responds to the physiological cues that govern seed development. For example, gibberellic acid (GA) regulates LEC1 activity during seed development (Hu et al ). As shown in Figure A, bioactive GA isoforms display a dynamic accumulation pattern, achieving highest levels during the early stages of seed development.…”

“…Bioactive GAs promote the degradation of DELLA proteins, releasing LEC1 to activate gene transcription. GAs have been shown to release LEC1 to activate the expression of YUCCA ( YUC ) genes involved in auxin biosynthesis (Hu et al ).…”

“…LEC1's function early in seed development is mediated, at least in part, through its direct activation of transcription factors involved in morphogenetic processes (Junker et al ; Pelletier et al ; Hu et al ). For example, LEC1 directly regulates the transcription of the HD‐ZIPIII transcription factors, PHABULOSA and PHAVOLUTA , that have been characterized as master regulators of apical fate early in embryogenesis and of SCARECROW , a key regulator of root architecture (Di Laurenzio et al ; Smith and Long ; Pelletier et al ).…”

CRK5 Protein Kinase Contributes to the Progression of Embryogenesis of Arabidopsis thaliana

“…Embryo polarity is determined during the proembryo stage with asymmetric division of the zygote [1], while morphogenesis characterizes early embryogenesis from the globular to the heart stage [2]. The late embryogenesis is marked by maturation (expansion of the cotyledons and the axis of the embryo without cell divisions) and ends in dormancy [3]. Maturation also leads to embryo desiccation and the accumulation of storage nutrients in the cotyledons of Arabidopsis [3,4].…”