Basic Helix-Loop-Helix Transcription Factors: Regulators for Plant Growth Development and Abiotic Stress Responses

Plant basic helix-loop-helix (bHLH) transcription factors are involved in many physiological processes, and they play important roles in the abiotic stress responses. The literature related to genome sequences has increased, with genome-wide studies on the bHLH transcription factors in plants. Researchers have detailed the functionally characterized bHLH transcription factors from different aspects in the model plant Arabidopsis thaliana, such as iron homeostasis and abiotic stresses; however, other important economic crops, such as rice, have not been summarized and highlighted. The bHLH members in the same subfamily have similar functions; therefore, unraveling their regulatory mechanisms will help us to identify and understand the roles of some of the unknown bHLH transcription factors in the same subfamily. In this review, we summarize the available knowledge on functionally characterized bHLH transcription factors according to four categories: plant growth and development; metabolism synthesis; plant signaling, and abiotic stress responses. We also highlight the roles of the bHLH transcription factors in some economic crops, especially in rice, and discuss future research directions for possible genetic applications in crop breeding.

Automated summary

Plant basic helix-loop-helix (bHLH) transcription factors are crucial in various physiological processes, particularly in response to abiotic stress. While the extensively studied bHLH transcription factors in Arabidopsis thaliana have been characterized in terms of iron homeostasis and abiotic stress, the significance of these factors in other economically important crops, such as rice, remains not fully explored. This review consolidates the current knowledge on functionally characterized bHLH transcription factors, categorizing them into plant growth and development, metabolism synthesis, plant signaling, and abiotic stress responses. Additionally, it highlights the roles of bHLH transcription factors, especially in rice, and discusses potential genetic applications in crop breeding.