ABI5 mediates light–ABA/GA crosstalk networks during seed germination

Abstract Appropriate timing of seed germination is crucial for plant survival and has important implications for agricultural production. Timely germination relies on harmonious interactions between endogenous developmental signals, especially abscisic acid (ABA) and gibberellins (GAs), and environmental cues such as light. Recently, a series of investigations with regard to the crosstalk between phytochromes, ABA, and GAs in the regulation of seed germination demonstrated that the transcription factor ABSCISIC ACID INSENSITIVE 5 (ABI5) is a central mediator in the light–ABA/GA cascades. Here, we review the information on ABI5 as a key player in light-, ABA-, and GA-signaling pathways to precisely control seed germination. We highlight the recent advances in ABI5-related studies, focusing on the regulation of seed germination, which is strictly controlled at both transcriptional and protein levels by numerous light-regulated factors. We further discuss the components of ABA- and GA-signaling pathways that could regulate ABI5 during seed germination, including transcription factors, E3 ligases, protein kinases, and phosphatases. The precise molecular mechanisms by which ABI5 mediates ABA–GA antagonistic crosstalk during seed germination are also described. Finally, some potential research hotspots underlying ABI5-mediated seed germination regulatory networks are proposed.