bZIP Transcription Factors: Structure, Modification, Abiotic Stress Responses and Application in Plant Improvement

Abstract

Plant growth, yield, and distribution are significantly impacted by abiotic stresses, affecting global ecosystems and forestry practices. However, plants have evolved complex adaptation mechanisms governed by numerous genes and transcription factors (TFs) to manage these stresses. Among these, bZIP (basic leucine zipper) is a crucial regulator orchestrating morphological adaptations. This review aims to elucidate the multifaceted roles of bZIP TFs in plant species. We discuss the morphological changes induced by stress stimuli and the pivotal functions of bZIP TFs in mediating these responses. While several publications have explored the mechanisms of bZIP TFs in response to abiotic stresses, this review delves into the intricate regulatory networks, summarizing alternative splicing and post-translational modifications, signaling networks interacting with bZIP TFs, and genetic engineering of bZIP TFs. By synthesizing current research, this review provides an updated discussion on bZIP interactions with other proteins to regulate stresses such as cold, heat, drought, and salt. Additionally, it offers avenues for future research and applications of bZIP TFs to improve abiotic stress resilience in plants through genetic engineering.

Keywords: abiotic stress; application; bZIP; modification.

Figure 1

Structure and classification of bZIP. (A) Sequence alignment of bZIP domain from 12 plant species, highlighting the fixed nuclear localization structure N-x7-R/K-x9. The domain is divided into the basic region and the leucine zipper domain. (B) Three-dimensional protein structures of Arabidopsis thaliana bZIP4. The left figure illustrates the flat bZIP strands assigned as chains E and F, with leucine residues labeled and their position numbers included. The right 3D protein structure depicts the globular form of AtbZIP4, highlighting the DNA-binding domain. (C) Phylogenetic tree of bZIP from four plant species, including Arabidopsis thaliana, Liriodendron chinense, Physcomitrella patens, and Oryza sativa. The phylogenetic classification was generated using MEGA (version 11) software with default parameters and a bootstrap value of 1000.

Figure 2

Post-translational modifications of bZIP TFs. The left panel illustrates the acetylation of bZIP TFs mediated by histone acetyltransferases and the deacetylation of bZIP TFs by histone deacetylases. Specifically, OsbZIP46 deacetylation mediated by the histone deacetylase OsHDA716 reduces chilling tolerance through the interplay between the chromatin regulator and the bZIP TF. The right panel depicts the phosphorylation and ubiquitination of bZIP TFs. SnRK2s mediate the ABA key signaling pathway to control transcription and stomatal aperture modulation. SnRK2.2 is responsible for ABA-induced phosphorylation at the threonine (T) site, while Raf-like protein kinases, including ABA and the ARK, act as upstream regulators of the SnRK2. During ubiquitination, the HY5 in Arabidopsis interacts with COP1 through phosphorylation reactions, leading to proteasome-mediated degradation and the addition of ubiquitin molecules to HY5.

Figure 3

Interaction of bZIP TFs with other proteins to regulate drought and salt stresses. AREB1 induces the transcription of drought-responsive genes such as LEA18, dehydrin, and HSP70 through ABA-mediated activation. Additionally, AREB1 induces the transcription of enzymes like SuSy and genes encoding AlaAT enzymes. bZIP2 TFs binds to ACGT elements in the promoter regions of MYB48, WD40, DHN15, and LEA to regulate salt and drought stresses.