Transcriptional and Post-Translational Regulation of Plant bHLH Transcription Factors during the Response to Environmental Stresses

Abstract

Over the past decades, extensive research has been conducted to identify and characterize various plant transcription factors involved in abiotic stress responses. Therefore, numerous efforts have been made to improve plant stress tolerance by engineering these transcription factor genes. The plant basic Helix–Loop–Helix (bHLH) transcription factor family represents one of the most prominent gene families and contains a bHLH motif that is highly conserved in eukaryotic organisms. By binding to specific positions in promoters, they activate or repress the transcription of specific response genes and thus affect multiple variables in plant physiology such as the response to abiotic stresses, which include drought, climatic variations, mineral deficiencies, excessive salinity, and water stress. The regulation of bHLH transcription factors is crucial to better control their activity. On the one hand, they are regulated at the transcriptional level by other upstream components; on the other hand, they undergo various modifications such as ubiquitination, phosphorylation, and glycosylation at the post-translational level. Modified bHLH transcription factors can form a complex regulatory network to regulate the expression of stress response genes and thus determine the activation of physiological and metabolic reactions. This review article focuses on the structural characteristics, classification, function, and regulatory mechanism of bHLH transcription factor expression at the transcriptional and post-translational levels during their responses to various abiotic stress conditions.

Abiotic Stress Signaling and Responses in Plants

“…In turn, Radani et al [12] focus in their article on the Helix-Loop-Helix (bHLH) plant family TFs, involved in responses to abiotic stress, representing one of the most important families of eukaryotic genes containing the highly conserved bHLH motif. These factors activate or repress the transcription of specific response genes and thus influence the response to abiotic stresses such as drought, climate change, mineral deficiencies, excessive salinity, and water stress, and the regulation of these factors is crucial in achieving a better control of their activity.…”

Expression Patterns and Molecular Mechanisms Regulating Drought Tolerance of Soybean [Glycine max (L.) Merr.] Conferred by Transcription Factor Gene GmNAC19

“…Due to their regulatory effects on many genes involved in adverse conditions, TFs are generally considered one of the most appropriate genetic targets for the molecular breeding and development of stress-tolerant crop varieties, e.g., inducing drought response in plants [12,13]. Studies have shown that a large number of TFs, e.g., NAC [14], AP2/ERF [15], bZIP [16], bHLH [17], MYB [18,19], and WRKY [20], are frequently involved in the plant response to water stress. In particular, NAC TFs are one of the largest families of plant-specific transcriptional regulators and are widely distributed in plants, including mosses, ferns, gymnosperms, and angiosperms [21,22].…”

Closely-Spaced Repetitions of CAMTA Trans-Factor Binding Sites in Promoters of Model Plant MEP Pathway Genes

“…A pivotal role in this process is played by cis-active elements localized in the gene promoter region, which are bound by particular transcription factors [17]. The activation of trans-factors, being a prerequisite to DNA-binding and gene expression regulation, is facilitated by numerous signaling routes, which adjust the gene expression level to the particular needs of cells [18,19]. External signals are delivered by activated gene-specific trans-factors to the multisubunit Mediator complex, interacting with general trans-factors complexed with RNA polymerase II [20].…”