Arabidopsis Basic Helix-Loop-Helix 34 (bHLH34) Is Involved in Glucose Signaling through Binding to a GAGA Cis-Element

Abstract

The modulation of glucose (Glc) homeostasis and signaling is crucial for plant growth and development. Nevertheless, the molecular signaling mechanism by which a plant senses a cellular Glc level and coordinates the expression of Glc-responsive genes is still incompletely understood. Previous studies have shown that Arabidopsis thaliana plasma membrane Glc-responsive regulator (AtPGR) is a component of the Glc-responsive pathway. Here, we demonstrated that a transcription factor bHLH34 binds to 5′-GAGA-3′ element of the promoter region of AtPGR in vitro, and activates beta-glucuronidase (GUS) activity upon Glc treatment in AtPGR promoter-GUS transgenic plants. Gain- and loss-of-function analyses suggested that the bHLH34 involved in the responses to not only Glc, but also abscisic acid (ABA) and salinity. These results suggest that bHLH34 functions as a transcription factor in the Glc-mediated stress responsive pathway as well as an activator of AtPGR transcription. Furthermore, genetic experiments revealed that in Glc response, the functions of bHLH34 are different from that of a bHLH104, a homolog of bHLH34. Collectively, our findings indicate that bHLH34 is a positive regulator of Glc, and may affect ABA or salinity response, whereas bHLH104 is a negative regulator and epistatic to bHLH34 in the Glc response.

Transcriptomic comparison between developing seeds of yellow- and black-seeded Brassica napus reveals that genes influence seed quality

“…BnTT8 (BnaC09g24870D and BnaA09g22810D) was also downregulated in yellow seed compared with black seed at specific stages, encoding the transcription factor bHLH as an important regulator throughout flavonoid biosynthesis. Another two bHLHs (BnaA01g17420D and BnaA01g24020D) were also downregulated, which have been proven to have functions in regulating jasmonate responses [54] and glucose homeostasis, and may affect ABA or salinity response in Arabidopsis [55]. In the present study, 21 CYPs were differentially expressed between yellow and black rapeseeds, although they were not shown to have functions in the secondary metabolism of B. napus.…”

Genome-wide identification and expression analysis of the bHLH transcription factor family and its response to abiotic stress in foxtail millet (Setaria italica L.)

“…Its expression was increased during seven stresses (acid, alkali, NaCl, heat, cold, flooding, and dark) but decreased significantly during PEG stress. AtbHLH34 , which belongs to the same subfamily 6 as SibHLH7 and has a similar motif composition, can interact with 5′-GAGA-3′ cis regulatory elements in vitro, and activates the transcription of planar AtPGR [ 70 ]. This enhances the resistance to abiotic stress.…”

TabHLH27 orchestrates root growth and drought tolerance to enhance water use efficiency in wheat

“…To unravel TabHLH27’s dual functional transcriptional activity—activating some genes while suppressing others—we probed potential interactions between TabHLH27 and other TFs, forming complexes to regulate downstream genes differently. By scrutinizing coexisting TF binding motifs with TabHLH27 (Min et al ., 2017; Toledo-Ortiz et al ., 2003) in the promoter accessible chromatin region (Shi et al ., 2022) of up-or down-regulated genes, we identified several co-factors with either activation or suppression activity ( Figure S5g) . Notably, TabZIP62-D1 and TaABI3-D1 emerged as top enriched co-factors for TabHLH27 activated and repressed genes, respectively ( Figure S5h ).…”