Brassinosteroid-Induced Transcriptional Repression and Dephosphorylation-Dependent Protein Degradation Negatively Regulate BIN2-Interacting AIF2 (a BR Signaling-Negative Regulator) bHLH Transcription Factor

Basic helix-loop-helix (bHLH) transcription factors constitute a superfamily in eukaryotes but their roles in plant immunity remain largely uncharacterized. We found that the transcript abundance in tomato leaves of one bHLH transcription factor-encoding gene, Nrd1 (negative regulator of resistance to DC3000 1), was significantly increased after treatment with the immunity-inducing flgII-28 peptide. Plants carrying a loss-of-function mutation in Nrd1 (Δnrd1) showed enhanced resistance to Pseudomonas syringae pv. tomato (Pst) DC3000 although early pattern-triggered immunity responses such as generation of reactive oxygen species and activation of mitogen-activated protein kinases after treatment with flagellin-derived flg22 and flgII-28 peptides were unaltered compared to wild-type plants. An RNA-Seq analysis identified a gene, Agp1, whose expression is strongly suppressed in an Nrd1-dependent manner. Agp1 encodes an arabinogalactan protein and overexpression of the Agp1 gene in Nicotiana benthamiana led to ~10-fold less Pst growth compared to the control. These results suggest that the Nrd1 protein promotes tomato susceptibility to Pst by suppressing the defense gene Agp1. RNA-Seq also revealed that loss of Nrd1 function has no effect on the transcript abundance of immunity-associated genes including Bti9, Core, Fls2, Fls3 and Wak1 upon Pst inoculation, suggesting that the enhanced immunity observed in the Δnrd1 mutants is due to the activation of key PRR signaling components as well as loss of Nrd1-regulated suppression of Agp1.

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INDEHISCENT regulates explosive seed dispersal

10.1101/2021.06.11.448014 ◽

2021 ◽

Author(s):

Anahit Galstyan ◽

Penny Sarchet ◽

Rafael Campos-Martin ◽

Milad Adibi ◽

Lachezar A Nikolov ◽

...

Keyword(s):

Transcription Factor ◽

Cell Types ◽

Negative Regulator ◽

Bhlh Transcription Factor ◽

Zone Formation ◽

Distinct Cell ◽

Developmental System Drift ◽

Dehiscence Zone ◽

Conserved Gene ◽

Open Question

How traits evolve to produce novelty or stasis is an open question in biology. We investigate this question in Cardamine hirsuta, a relative of Arabidopsis thaliana that employs explosive fracture to disperse its seeds. This trait evolved through key morphomechanical innovations that distinguish the otherwise very similar, dehiscent fruit of these two species. Using CRISPR/Cas9, we show that dehiscence zone formation is absolutely required for explosive fracture in C. hirsuta, and is controlled by the bHLH transcription factor INDEHISCENT (IND). Using mutant screens, we identified the MADS-box transcription factor FRUITFULL (FUL) as a negative regulator of IND in C. hirsuta. Although FUL function is conserved in C. hirsuta, the consequences of IND mis-expression differ in ful mutants of C. hirsuta versus A. thaliana. In ful mutants of both species, valve tissue is replaced by dehiscence zone tissue, which comprises two distinct cell types: lignified layer and separation layer cells. While A. thaliana ful mutants develop stunted fruit with ectopic lignified layer cells, C. hirsuta ful mutants have elongated fruit with ectopic separation layer cells. We show that IND dose determines the proportion of these two cell types in ectopic dehiscence zones. We also show that the extent of ectopic lignification caused by IND mis-expression determines fruit length. Our findings indicate developmental system drift in the conserved gene network patterning dehiscent fruit in two related Brassicaceae species.

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

Molecular and Cellular Biology ◽

10.1128/mcb.16.2.626 ◽

1996 ◽

Vol 16 (2) ◽

pp. 626-633 ◽

Cited By ~ 39

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.

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Faculty Opinions recommendation of bHLH transcription factor Olig1 is required to repair demyelinated lesions in the CNS.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1023116.264810 ◽

2005 ◽

Author(s):

Magdalena Goetz

Keyword(s):

Transcription Factor ◽

Bhlh Transcription Factor

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Faculty Opinions recommendation of Mutation of a bHLH transcription factor allowed almond domestication.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.735980063.793561372 ◽

2019 ◽

Author(s):

François Parcy

Keyword(s):

Transcription Factor ◽

Bhlh Transcription Factor

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Conserved and non-conserved functions of the rice homologs of the Arabidopsis trichome initiation-regulating MBW complex proteins

BMC Plant Biology ◽

10.1186/s12870-021-03035-0 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Kaijie Zheng ◽

Xutong Wang ◽

Yating Wang ◽

Shucai Wang

Keyword(s):

Transcription Factor ◽

Anthocyanin Biosynthesis ◽

Transcriptional Activator ◽

Myb Transcription Factor ◽

Bhlh Transcription Factor ◽

Seed Color ◽

Transcription Activator ◽

Root Hair Formation ◽

Protoplast Transfection ◽

Mbw Complex

Abstract Background Trichome initiation in Arabidopsis is regulated by a MYB-bHLH-WD40 (MBW) transcriptional activator complex formed by the R2R3 MYB transcription factor GLABRA1 (GL1), MYB23 or MYB82, the bHLH transcription factor GLABRA3 (GL3), ENHANCER OF GLABRA3 (EGL3) or TRANSPARENT TESTA8 (TT8), and the WD40-repeat protein TRANSPARENT TESTA GLABRA1 (TTG1). However, the functions of the rice homologs of the MBW complex proteins remained uncharacterized. Results Based on amino acid sequence identity and similarity, and protein interaction prediction, we identified OsGL1s, OsGL3s and OsTTG1s as rice homologs of the MBW complex proteins. By using protoplast transfection, we show that OsGL1D, OsGL1E, OsGL3B and OsTTG1A were predominantly localized in the nucleus, OsGL3B functions as a transcriptional activator and is able to interact with GL1 and TTG1. By using yeast two-hybrid and protoplast transfection assays, we show that OsGL3B is able to interact with OsGL1E and OsTTG1A, and OsGL1E and OsTTG1A are also able to interact with GL3. On the other hand, we found that OsGL1D functions as a transcription activator, and it can interact with GL3 but not OsGL3B. Furthermore, our results show that expression of OsTTG1A in the ttg1 mutant restored the phenotypes including alternations in trichome and root hair formation, seed color, mucilage production and anthocyanin biosynthesis, indicating that OsTTG1A and TTG1 may have similar functions. Conclusion These results suggest that the rice homologs of the Arabidopsis MBW complex proteins are able to form MBW complexes, but may have conserved and non-conserved functions.

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