Arabidopsis CIB3 regulates photoperiodic flowering in an FKF1-dependent way

2021 ◽  
Author(s):  
Lianxia Zhou ◽  
Yi Lu ◽  
Jie Huang ◽  
Zhiwei Sha ◽  
Weiliang Mo ◽  
...  
Keyword(s):  
Blue Light ◽  
Light Regulation ◽  
Bhlh Transcription Factor ◽  
Flowering Locus T ◽  
Helix Loop Helix ◽  
Photoperiodic Flowering ◽  
E Box ◽  
Cryptochrome 2 ◽  
Flavin Binding ◽  
Regulation Of Growth

ABSTRACT Arabidopsis cryptochrome 2 (CRY2) and FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1) are blue light receptors mediating light regulation of growth and development, such as photoperiodic flowering. CRY2 interacts with a basic helix-loop-helix (bHLH) transcription factor CIB1 in response to blue light to activate the transcription of the flowering integrator gene FLOWERING LOCUS T (FT). CIB1, CIB2, CIB4 and CIB5 function redundantly to promote flowering in a CRY2-dependent way and form various heterodimers to bind to the non-canonical E-box sequence in the FT promoter. However, the function of CIB3 has not been described. We discovered that CIB3 promotes photoperiodic flowering independently of CRY2. Moreover, CIB3 does not interact with CRY2 but interacts with CIB1 and functions synergistically with CIB1 to promote transcription of the GI gene. FKF1 is required for CIB3 to promote flowering and enhances the CIB1-CIB3 interaction in response to blue light.

scholarly journals Cryptochrome 2 from Lilium × formolongi Regulates Photoperiodic Flowering in Transgenic Arabidopsis thaliana

2021 ◽  
Vol 22 (23) ◽  
pp. 12929
Author(s):  
Xiao-Mei Wu ◽  
Zheng-Min Yang ◽  
Lin-Hao Yang ◽  
Ji-Ren Chen ◽  
Hai-Xia Chen ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Blue Light ◽  
Floral Induction ◽  
Vital Role ◽  
Helix Loop Helix ◽  
Photoperiodic Flowering ◽  
Photoperiodic Regulation ◽  
Highly Sensitive ◽  
Cryptochrome 2 ◽  
Seed Propagation

The photoperiodic flowering pathway is essential for plant reproduction. As blue and ultraviolet-A light receptors, cryptochromes play an important role in the photoperiodic regulation of flowering. Lilium × formolongi is an important cut flower that flowers within a year after seed propagation. Floral induction is highly sensitive to photoperiod. In this study, we isolated the CRYPTOCHROME2 gene (LfCRY2) from L. × formolongi. The predicted LfCRY2 protein was highly homologous to other CRY2 proteins. The transcription of LfCRY2 was induced by blue light. LfCRY2 exhibits its highest diurnal expression during the floral induction stage under both long-day and short-day photoperiods. Overexpression of LfCRY2 in Arabidopsis thaliana promoted flowering under long days but not short days, and inhibited hypocotyl elongation under blue light. Furthermore, LfCRY2 was located in the nucleus and could interact with L. × formolongi CONSTANS-like 9 (LfCOL9) and A. thaliana CRY-interacting basic-helix-loop-helix 1 (AtCIB1) in both yeast and onion cells, which supports the hypothesis that LfCRY2 hastens the floral transition via the CIB1-CO pathway in a manner similar to AtCRY2. These results provide evidence that LfCRY2 plays a vital role in promoting flowering under long days in L. × formolongi.

scholarly journals Characterization of the FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 Homolog SlFKF1 in Tomato as a Model for Plants with Fleshy Fruit

2021 ◽  
Vol 22 (4) ◽  
pp. 1735
Author(s):  
Tomoki Shibuya ◽  
Manabu Nishiyama ◽  
Kazuhisa Kato ◽  
Yoshinori Kanayama
Keyword(s):  
Blue Light ◽  
Physiological Role ◽  
Regulatory Elements ◽  
Fleshy Fruit ◽  
High Sequence Identity ◽  
Phylogenetic Tree Analysis ◽  
Blue Light Receptor ◽  
Photoperiodic Flowering ◽  
Single Flower ◽  
Flavin Binding

FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1) is a blue-light receptor whose function is related to flowering promotion under long-day conditions in Arabidopsis thaliana. However, information about the physiological role of FKF1 in day-neutral plants and even the physiological role other than photoperiodic flowering is lacking. Thus, the FKF1 homolog SlFKF1 was investigated in tomato, a day-neutral plant and a useful model for plants with fleshy fruit. It was confirmed that SlFKF1 belongs to the FKF1 group by phylogenetic tree analysis. The high sequence identity with A. thaliana FKF1, the conserved amino acids essential for function, and the similarity in the diurnal change in expression suggested that SlFKF1 may have similar functions to A. thaliana FKF1. CONSTANS (CO) is a transcription factor regulated by FKF1 and is responsible for the transcription of genes downstream of CO. cis-Regulatory elements targeted by CO were found in the promoter region of SINGLE FLOWER TRUSS (SFT) and RIN, which are involved in the regulation of flowering and fruit ripening, respectively. The blue-light effects on SlFKF1 expression, flowering, and fruit lycopene concentration have been observed in this study and previous studies. It was confirmed in RNA interference lines that the low expression of SlFKF1 is associated with late flowering with increased leaflets and low lycopene concentrations. This study sheds light on the various physiological roles of FKF1 in plants.

scholarly journals The MNT transcription factor autoregulates its expression and supports proliferation in MYC-associated factor X (MAX)-deficient cells

2020 ◽  
Vol 295 (7) ◽  
pp. 2001-2017 ◽  
Author(s):  
M. Carmen Lafita-Navarro ◽  
Judit Liaño-Pons ◽  
Andrea Quintanilla ◽  
Ignacio Varela ◽  
Rosa Blanco ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Transcription Factor ◽  
Transcriptional Regulator ◽  
Bhlh Transcription Factor ◽  
Factor X ◽  
Associated Factor ◽  
Helix Loop Helix ◽  
E Box ◽  
E Boxes ◽  
Cycle Regulation

The MAX network transcriptional repressor (MNT) is an MXD family transcription factor of the basic helix-loop-helix (bHLH) family. MNT dimerizes with another transcriptional regulator, MYC-associated factor X (MAX), and down-regulates genes by binding to E-boxes. MAX also dimerizes with MYC, an oncogenic bHLH transcription factor. Upon E-box binding, the MYC–MAX dimer activates gene expression. MNT also binds to the MAX dimerization protein MLX (MLX), and MNT–MLX and MNT–MAX dimers co-exist. However, all MNT functions have been attributed to MNT–MAX dimers, and no functions of the MNT–MLX dimer have been described. MNT's biological role has been linked to its function as a MYC oncogene modulator, but little is known about its regulation. We show here that MNT localizes to the nucleus of MAX-expressing cells and that MNT–MAX dimers bind and repress the MNT promoter, an effect that depends on one of the two E-boxes on this promoter. In MAX-deficient cells, MNT was overexpressed and redistributed to the cytoplasm. Interestingly, MNT was required for cell proliferation even in the absence of MAX. We show that in MAX-deficient cells, MNT binds to MLX, but also forms homodimers. RNA-sequencing experiments revealed that MNT regulates the expression of several genes even in the absence of MAX, with many of these genes being involved in cell cycle regulation and DNA repair. Of note, MNT–MNT homodimers regulated the transcription of some genes involved in cell proliferation. The tight regulation of MNT and its functionality even without MAX suggest a major role for MNT in cell proliferation.

scholarly journals BETA3, a novel helix-loop-helix protein, can act as a negative regulator of BETA2 and MyoD-responsive genes.

1996 ◽  
Vol 16 (2) ◽  
pp. 626-633 ◽  
Author(s):  
M Peyton ◽  
C M Stellrecht ◽  
F J Naya ◽  
H P Huang ◽  
P J Samora ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Negative Regulator ◽  
Bhlh Transcription Factor ◽  
Pcr Cloning ◽  
Specific Expression ◽  
Class A ◽  
Helix Loop Helix ◽  
E Box ◽  
Class B ◽  
Bhlh Factors

Using degenerate PCR cloning we have identified a novel basic helix-loop-helix (bHLH) transcription factor, BETA3, from a hamster insulin tumor (HIT) cell cDNA library. Sequence analysis revealed that this factor belongs to the class B bHLH family and has the highest degree of homology with another bHLH transcription factor recently isolated in our laboratory, BETA2 (neuroD) (J. E. Lee, S. M. Hollenberg, L. Snider, D. L. Turner, N. Lipnick, and H. Weintraub, Science 268:836-844, 1995; F. J. Naya, C. M. M. Stellrecht, and M.-J. Tsai, Genes Dev. 8:1009-1019, 1995). BETA2 is a brain- and pancreatic-islet-specific bHLH transcription factor and is largely responsible for the tissue-specific expression of the insulin gene. BETA3 was found to be tissue restricted, with the highest levels of expression in HIT, lung, kidney, and brain cells. Surprisingly, despite the homology between BETA2 and BETA3 and its intact basic region, BETA3 is unable to bind the insulin E box in bandshift analysis as a homodimer or as a heterodimer with the class A bHLH factors E12, E47, or BETA1. Instead, BETA3 inhibited both the E47 homodimer and the E47/BETA2 heterodimer binding to the insulin E box. In addition, BETA3 greatly repressed the BETA2/E47 induction of the insulin enhancer in HIT cells as well as the MyoD/E47 induction of a muscle-specific E box in the myoblast cell line C2C12. In contrast, expression of BETA3 had no significant effect on the GAL4-VP16 transcriptional activity. Immunoprecipitation analysis demonstrates that the mechanism of repression is via direct protein-protein interaction, presumably by heterodimerization between BETA3 and class A bHLH factors.

scholarly journals Modulation of the Expression and Transactivation of Androgen Receptor by the Basic Helix-Loop-Helix Transcription Factor Pod-1 through Recruitment of Histone Deacetylase 1

2005 ◽  
Vol 19 (9) ◽  
pp. 2245-2257 ◽  
Author(s):  
Cheol Yi Hong ◽  
Eun-Yeung Gong ◽  
Kabsun Kim ◽  
Ji Ho Suh ◽  
Hyun-Mi Ko ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Androgen Receptor ◽  
Histone Deacetylase ◽  
Promoter Activity ◽  
Bhlh Transcription Factor ◽  
Dependent Manner ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box ◽  
And Function

Abstract Androgen receptor (AR) is important in male sexual differentiation and testicular function. Here, we demonstrate the regulation of AR expression and its transactivation by the basic helix-loop-helix (bHLH) transcription factor Pod-1, the expression of which in postnatal testis reciprocally coincides with the expression of AR. Pod-1 represses the promoter activity of AR, possibly through its E-box. An AR promoter region of 169 bp, which harbors one canonical E-box, is sufficient for the Pod-1-repression and bound by purified Pod-1 proteins. Pod-1 also suppresses the transactivation of AR. Transient transfection analyses of mammalian cells show that Pod-1 represses AR transactivation in a dose-dependent manner. Furthermore, yeast two-hybrid, glutathione-S-transferase-pull-down, and coimmunoprecipitation analyses reveal that Pod-1 directly associates with AR through its N-terminal region and through the DNA binding-hinge domain of AR. Interestingly, Pod-1 recruits histone deacetylase (HDAC)-1 to inhibit both promoter activity and transactivation of AR. Overexpression of HDAC1 further inhibits the Pod-1-mediated repressions and Pod-1 directly interacts with HDAC1. Furthermore, chromatin immunoprecipitation assay reveals that HDAC1 is recruited with Pod-1 to the endogenous AR promoter and the androgen-regulated Pem promoter. Taken together, these results suggest that Pod-1, which controls AR transcription and function, may play an important role in the development and function of the testis.

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