Updated Mechanisms of GCN5—The Monkey King of the Plant Kingdom in Plant Development and Resistance to Abiotic Stresses

Histone modifications are the main epigenetic mechanisms that regulate gene expression, chromatin structure, and plant development, among which histone acetylation is one of the most important and studied epigenetic modifications. Histone acetylation is believed to enhance DNA access and promote transcription. GENERAL CONTROL NON-REPRESSIBLE 5 (GCN5), a well-known enzymatic protein responsible for the lysine acetylation of histone H3 and H4, is a universal and crucial histone acetyltransferase involved in gene transcription and plant development. Many studies have found that GCN5 plays important roles in the different development stages of Arabidopsis. In terms of exogenous stress conditions, GCN5 is also involved in the responses to heat stress, cold stress, and nutrient element deficiency by regulating the related gene expression to maintain the homeostasis of some key metabolites (e.g., cellulose) or ions (e.g., phosphate, iron); in addition, GCN5 is involved in the phytohormone pathways such as ethylene, auxin, and salicylic acid to play various roles during the plant lifecycle. Some of the pathways involved by GCN5 also interwind to regulate specific physiological processes or developmental stages. Here, interactions between various developmental events and stress-resistant pathways mediated by GCN5 are comprehensively addressed and the underlying mechanisms are discussed in the plant. Studies with some interacting factors such as ADA2b provided valuable information for the complicated histone acetylation mechanisms. We also suggest the future focuses for GCN5 functions and mechanisms such as functions in seed development/germination stages, exploration of novel interaction factors, identification of more protein substrates, and application of advanced biotechnology-CRISPR in crop genetic improvement, which would be helpful for the complete illumination of roles and mechanisms of GCN5.