scholarly journals Constitutive Steroidal Glycoalkaloid Biosynthesis in Tomato is Regulated by the Clade IIIe Basic Helix-Loop-Helix Transcription Factors MYC1 and MYC2

2020 ◽  
Author(s):  
Gwen Swinnen ◽  
Margaux De Meyer ◽  
Jacob Pollier ◽  
Francisco Javier Molina-Hidalgo ◽  
Evi Ceulemans ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Regulatory Element ◽  
Cholesterol Biosynthesis ◽  
Constitutive Expression ◽  
Defense Compounds ◽  
Specialized Metabolites ◽  
Jasmonate Signaling ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Bhlh Transcription Factors

ABSTRACTSpecialized metabolites are produced by plants to fend off biotic enemies. Across the plant kingdom, the biosynthesis of these defense compounds is promoted by jasmonate signaling in which clade IIIe basic helix-loop-helix (bHLH) transcription factors take on a central role. Tomato (Solanum lycopersicum) produces cholesterol-derived steroidal glycoalkaloids (SGAs) that act as phytoanticipins against a broad variety of herbivores and pathogens. The biosynthesis of SGAs from cholesterol occurs constitutively in tomato plants and can be further stimulated by jasmonates. Here, we demonstrate that the two tomato clade IIIe bHLH transcription factors, MYC1 and MYC2, redundantly and specifically control the constitutive biosynthesis of SGAs. Double myc1 myc2 loss-of-function tomato hairy roots displayed suppressed constitutive expression of cholesterol and SGA biosynthesis genes, and consequently severely reduced levels of the main tomato SGAs α-tomatine and dehydrotomatine. In contrast, basal expression of genes involved in canonical jasmonate signaling or in the biosynthesis of highly jasmonate-inducible phenylpropanoid-polyamine conjugates was not affected. Furthermore, CRISPR-Cas9(VQR)-mediated genome editing of a specific cis-regulatory element, targeted by MYC1/2, in the promoter of a cholesterol biosynthesis gene led to decreased constitutive expression of this gene, but did not affect its jasmonate inducibility. Our results demonstrate that clade IIIe bHLH transcriptional regulators might have evolved to regulate the biosynthesis of specific constitutively accumulating specialized metabolites independent of jasmonate signaling.One sentence summaryThe clade IIIe basic helix-loop-helix transcription factors MYC1 and MYC2 control the constitutive biosynthesis of tomato steroidal glycoalkaloids and might do so independently of jasmonate signaling.

scholarly journals Specific Protein-Protein Interaction between Basic Helix-Loop-Helix Transcription Factors and Homeoproteins of the Pitx Family

2000 ◽  
Vol 20 (13) ◽  
pp. 4826-4837 ◽  
Author(s):  
Gino Poulin ◽  
Mélanie Lebel ◽  
Michel Chamberland ◽  
Francois W. Paradis ◽  
Jacques Drouin
Keyword(s):  
Transcription Factors ◽  
Critical Role ◽  
Specific Protein ◽  
Physical Interaction ◽  
Protein Protein Interaction ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Bhlh Factors ◽  
Pomc Gene ◽  
Bhlh Transcription Factors

ABSTRACT Homeoproteins and basic helix-loop-helix (bHLH) transcription factors are known for their critical role in development and cellular differentiation. The pituitary pro-opiomelanocortin (POMC) gene is a target for factors of both families. Indeed, pituitary-specific transcription of POMC depends on the action of the homeodomain-containing transcription factor Pitx1 and of bHLH heterodimers containing NeuroD1. We now show lineage-restricted expression of NeuroD1 in pituitary corticotroph cells and a direct physical interaction between bHLH heterodimers and Pitx1 that results in transcriptional synergism. The interaction between the bHLH and homeodomains is restricted to ubiquitous (class A) bHLH and to the Pitx subfamily. Since bHLH heterodimers interact with Pitx factors through their ubiquitous moiety, this mechanism may be implicated in other developmental processes involving bHLH factors, such as neurogenesis and myogenesis.

scholarly journals Basic Helix-Loop-Helix Transcription Factor Heterocomplex of Yas1p and Yas2p Regulates Cytochrome P450 Expression in Response to Alkanes in the Yeast Yarrowia lipolytica

2007 ◽  
Vol 6 (4) ◽  
pp. 734-743 ◽  
Author(s):  
Setsu Endoh-Yamagami ◽  
Kiyoshi Hirakawa ◽  
Daisuke Morioka ◽  
Ryouichi Fukuda ◽  
Akinori Ohta
Keyword(s):  
Cytochrome P450 ◽  
Transcription Factors ◽  
Yarrowia Lipolytica ◽  
Bhlh Protein ◽  
Genome Database ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Bhlh Transcription Factors

ABSTRACT The expression of the ALK1 gene, which encodes cytochrome P450, catalyzing the first step of alkane oxidation in the alkane-assimilating yeast Yarrowia lipolytica, is highly regulated and can be induced by alkanes. Previously, we identified a cis-acting element (alkane-responsive element 1 [ARE1]) in the ALK1 promoter. We showed that a basic helix-loop-helix (bHLH) protein, Yas1p, binds to ARE1 in vivo and mediates alkane-dependent transcription induction. Yas1p, however, does not bind to ARE1 by itself in vitro, suggesting that Yas1p requires another bHLH protein partner for its DNA binding, as many bHLH transcription factors function by forming heterodimers. To identify such a binding partner of Yas1p, here we screened open reading frames encoding proteins with the bHLH motif from the Y. lipolytica genome database and identified the YAS2 gene. The deletion of the YAS2 gene abolished the alkane-responsive induction of ALK1 transcription and the growth of the yeast on alkanes. We revealed that Yas2p has transactivation activity. Furthermore, Yas1p and Yas2p formed a protein complex that was required for the binding of these proteins to ARE1. These findings allow us to postulate a model in which bHLH transcription factors Yas1p and Yas2p form a heterocomplex and mediate the transcription induction in response to alkanes.

scholarly journals The effector FEP3/IRON MAN1 modulates interaction between BRUTUS-LIKE1 and bHLH subgroup IVb and IVc proteins

2021 ◽  
Author(s):  
Daniela M. Lichtblau ◽  
Birte Schwarz ◽  
Dibin Baby ◽  
Christopher Endres ◽  
Christin Sieberg ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Higher Plants ◽  
Deletion Mapping ◽  
Functional Protein ◽  
E3 Ligases ◽  
Interaction Sites ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Bhlh Transcription Factors ◽  
Bhlh Proteins

Plants use the micronutrient iron (Fe) efficiently to balance the requirements for Fe during growth with its potential cytotoxic effects. A cascade of basic helix-loop-helix (bHLH) transcription factors is initiated by bHLH proteins of the subgroups IVb and IVc. This induces more than 50 genes in higher plants that can be grouped in co-expression clusters. Gene co-expression networks contain information on functional protein interactomes. We conducted a targeted yeast two-hybrid screen with pairwise combinations of 23 proteins stemming from previously characterized Fe-deficiency-induced gene co-expression clusters and regulators. We identified novel and described interactions, as well as interaction hubs with multiple interactions within the network. We found that BRUTUS-LIKE E3 ligases (BTSL1, BTSL2) interacted with basic helix-loop-helix (bHLH) transcription factors of the subgroups IVb and IVc including PYE, bHLH104 and ILR3, and with small FE UPTAKE-INDUCING PEPTIDE3/IRON MAN1 (FEP3/IMA1). Through deletion studies and with support of molecular docking, we mapped the interaction sites to three-amino-acid regions in BTSL1 and FEP3/IMA1. The FEP3/IMA1 active residues are present in interacting sites of the bHLH IVc factors. FEP3/IMA1 attenuated interaction of BTSL1 with bHLH proteins in a quantitative yeast three-hybrid assay suggesting that it is an inhibitor. Co-expression of BTSL1 and bHLH IVb and IVc factors uncovered unexpected patterns of subcellular localization. Combining deletion mapping, protein interaction and physiological analysis, we discuss the model that FEP3/IMA1 is a small effector protein inhibiting BTSL1/BTSL2-mediated degradation of bHLH subgroup IVb and IVc proteins.

scholarly journals Calcium Regulation of Myogenesis by Differential Calmodulin Inhibition of Basic Helix-Loop-Helix Transcription Factors

2008 ◽  
Vol 19 (6) ◽  
pp. 2509-2519 ◽  
Author(s):  
Jannek Hauser ◽  
Juha Saarikettu ◽  
Thomas Grundström
Keyword(s):  
Transcription Factors ◽  
Target Genes ◽  
Myogenic Differentiation ◽  
Bhlh Protein ◽  
Channel Blockers ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Protein ◽  
Bhlh Transcription Factors

The members of the MyoD family of basic helix-loop-helix (bHLH) transcription factors are critical regulators of skeletal muscle differentiation that function as heterodimers with ubiquitously expressed E-protein bHLH transcription factors. These heterodimers must compete successfully with homodimers of E12 and other E-proteins to enable myogenesis. Here, we show that E12 mutants resistant to Ca2+-loaded calmodulin (CaM) inhibit MyoD-initiated myogenic conversion of transfected fibroblasts. Ca2+ channel blockers reduce, and Ca2+ stimulation increases, transcription by coexpressed MyoD and wild-type E12 but not CaM-resistant mutant E12. Furthermore, CaM-resistant E12 gives lower MyoD binding and higher E12 binding to a MyoD-responsive promoter in vivo and cannot rescue myogenic differentiation that has been inhibited by siRNA against E12 and E47. Our data support the concept that Ca2+-loaded CaM enables myogenesis by inhibiting DNA binding of E-protein homodimers, thereby promoting occupancy of myogenic bHLH protein/E-protein heterodimers on promoters of myogenic target genes.

Differential regulation of granulopoiesis by the basic helix-loop-helix transcriptional inhibitors Id1 and Id2

Blood ◽  
2005 ◽  
Vol 105 (11) ◽  
pp. 4272-4281 ◽  
Author(s):  
Miranda Buitenhuis ◽  
Hanneke W. M. van Deutekom ◽  
Liesbeth P. Verhagen ◽  
Anders Castor ◽  
Sten Eirik W. Jacobsen ◽  
...  
Keyword(s):  
Critical Role ◽  
Ectopic Expression ◽  
Constitutive Expression ◽  
Retroviral Transduction ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Cd34 Cells ◽  
Final Maturation ◽  
Inhibitor Of Dna Binding

Abstract Inhibitor of DNA binding (Id) proteins function as inhibitors of members of the basic helix-loop-helix family of transcription factors and have been demonstrated to play an important role in regulating lymphopoiesis. However, the role of these proteins in regulation of myelopoiesis is currently unclear. In this study, we have investigated the role of Id1 and Id2 in the regulation of granulopoiesis. Id1 expression was initially up-regulated during early granulopoiesis, which was then followed by a decrease in expression during final maturation. In contrast, Id2 expression was up-regulated in terminally differentiated granulocytes. In order to determine whether Id expression plays a critical role in regulating granulopoiesis, Id1 and Id2 were ectopically expressed in CD34+ cells by retroviral transduction. Our experiments demonstrate that constitutive expression of Id1 inhibits eosinophil development, whereas in contrast neutrophil differentiation was modestly enhanced. Constitutive Id2 expression accelerates final maturation of both eosinophils and neutrophils, whereas inhibition of Id2 expression blocks differentiation of both lineages. Transplantation of β2-microglobulin-/- nonobese diabetic severe combined immunodeficient (NOD/SCID) mice with CD34+ cells ectopically expressing Id1 resulted in enhanced neutrophil development, whereas ectopic expression of Id2 induced both eosinophil and neutrophil development. These data demonstrate that both Id1 and Id2 play a critical, although differential role in granulopoiesis.

scholarly journals The Basic Helix-Loop-Helix Transcription Factor Cph2 Regulates Hyphal Development in CandidaalbicansPartly via Tec1

2001 ◽  
Vol 21 (19) ◽  
pp. 6418-6428 ◽  
Author(s):  
Shelley Lane ◽  
Song Zhou ◽  
Ting Pan ◽  
Qian Dai ◽  
Haoping Liu
Keyword(s):  
Transcription Factor ◽  
Protein Kinase ◽  
Binding Sites ◽  
Regulatory Element ◽  
Ectopic Expression ◽  
Mitogen Activated Protein Kinase ◽  
Northern Analysis ◽  
Hyphal Development ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix

ABSTRACT Candida albicans undergoes a morphogenetic switch from budding yeast to hyphal growth form in response to a variety of stimuli and growth conditions. Multiple signaling pathways, including a Cph1-mediated mitogen-activated protein kinase pathway and an Efg1-mediated cyclic AMP/protein kinase A pathway, regulate the transition. Here we report the identification of a basic helix-loop-helix transcription factor of the Myc subfamily (Cph2) by its ability to promote pseudohyphal growth inSaccharomyces cerevisiae. Like sterol response element binding protein 1, Cph2 has a Tyr instead of a conserved Arg in the basic DNA binding region. Cph2 regulates hyphal development in C. albicans, ascph2/cph2 mutant strains show medium-specific impairment in hyphal development and in the induction of hypha-specific genes. However, many hypha-specific genes do not have potential Cph2 binding sites in their upstream regions. Interestingly, upstream sequences of all known hypha-specific genes are found to contain potential binding sites for Tec1, a regulator of hyphal development. Northern analysis shows that TEC1 transcription is highest in the medium in which cph2/cph2 displays a defect in hyphal development, and Cph2 is necessary for this transcriptional induction of TEC1. In vitro gel mobility shift experiments show that Cph2 directly binds to the two sterol regulatory element 1-like elements upstream of TEC1. Furthermore, the ectopic expression of TEC1 suppresses the defect ofcph2/cph2 in hyphal development. Therefore, the function of Cph2 in hyphal transcription is mediated, in part, through Tec1. We further show that this function of Cph2 is independent of the Cph1- and Efg1-mediated pathways.

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