Post-translational Modifications of bZIP Transcription Factors in Abscisic Acid Signaling and Drought Responses

Abstract

Under drought stress, plants have developed various mechanisms to survive in the reduced water supply, of which the regulation of stress-related gene expression is responsible for several transcription factors. The basic leucine zippers (bZIPs) are one of the largest and most diverse transcription factor families in plants. Among the 10 Arabidopsis bZIP groups, group A bZIP transcription factors function as a positive or negative regulator in ABA signal transduction and drought stress response. These bZIP transcription factors, which are involved in the drought response, have also been isolated in various plant species such as rice, pepper, potato, and maize. Recent studies have provided substantial evidence that many bZIP transcription factors undergo the post-translational modifications, through which the regulation of their activity or stability affects plant responses to various intracellular or extracellular stimuli. This review aims to address the modulation of the bZIP proteins in ABA signaling and drought responses through phosphorylation, ubiquitination and sumoylation.

Keywords: Abscisic acid; bZIP transcription factor; drought resistance; drought stress; gene expression; post-translational modification.

Fig. (1)

Biological functions of bZIP transcription factors for each group. The plant bZIP proteins function in the various cellular processes of stress responses and development. Functional characteristics and representative bZIP proteins were shown for each group. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (2)

Simplified overview of post-translational modifications that regulate bZIP protein activity and stability to modulate ABA signaling and drought stress response. In response to dehydration stress, ABA is biosynthesized, and E3 ligases and SUMO E3 ligase SIZ1 are influenced. ABA-activated SnRK2-type kinases and CPKs phosphorylate bZIP protein to activate transcriptional function. E3 ligase ubiquitinates bZIP protein and polyubiquitinated bZIP is degraded by 26S proteasome. SIZ1 sumoylates bZIP protein and sumoylated bZIP is stabilized. The activation of bZIP protein can be increased as much as sumoylated protein is accumulated, but SUMO conjugation can inactivate bZIP protein by preventing phosphorylation. SUMO protease desumoylates bZIP protein. (A higher resolution / colour version of this figure is available in the electronic copy of the article).