scholarly journals Copper Response Element and Crr1-Dependent Ni2+-Responsive Promoter for Induced, Reversible Gene Expression in Chlamydomonas reinhardtii

2003 ◽  
Vol 2 (5) ◽  
pp. 995-1002 ◽  
Author(s):  
Jeanette M. Quinn ◽  
Janette Kropat ◽  
Sabeeha Merchant
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Chlamydomonas Reinhardtii ◽  
Target Genes ◽  
Response Regulator ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Nickel Ions ◽  
Cobalt Ions ◽  
Inducible Gene

ABSTRACT The Cpx1 and Cyc6 genes of Chlamydomonas reinhardtii are activated in copper-deficient cells via a signal transduction pathway that requires copper response elements (CuREs) and a copper response regulator defined by the CRR1 locus. The two genes can also be activated by provision of nickel or cobalt ions in the medium. The response to nickel ions requires at least one CuRE and also CRR1 function, suggesting that nickel interferes with a component in the nutritional copper signal transduction pathway. Nickel does not act by preventing copper uptake/utilization because (i) holoplastocyanin formation is unaffected in Ni2+-treated cells and (ii) provision of excess copper cannot reverse the Ni-dependent activation of the target genes. The CuRE is sufficient for conferring Ni-responsive expression to a reporter gene, which suggests that the system has practical application as a vehicle for inducible gene expression. The inducer can be removed either by replacing the medium or by chelating the inducer with excess EDTA, either of which treatments reverses the activation of the target genes.

scholarly journals An absolute requirement for Cubitus interruptus in Hedgehog signaling

Development ◽  
2001 ◽  
Vol 128 (5) ◽  
pp. 733-742 ◽  
Author(s):  
N. Methot ◽  
K. Basler
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Hedgehog Signaling ◽  
Target Gene ◽  
Target Genes ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Cubitus Interruptus ◽  
Target Gene Expression ◽  
Hh Signaling

Hedgehog (Hh) proteins play diverse organizing roles in animal development by regulating gene expression in responding cells. Several components of the Hh signal transduction pathway have been identified, yet their precise role in mediating the various outputs of the pathway is still poorly understood. The Gli homolog Cubitus interruptus (Ci) is involved in controlling the transcription of Drosophila Hh target genes and thus represents the most downstream component known in this pathway. We address the question of whether the Hh pathway is distally branched or, in other words, whether the regulation of Ci activity is the sole output of Hh signaling. Putative Ci-independent branches of Hh signaling are explored by analyzing the behavior of cells that lack Ci but have undergone maximal activation of the Hh transduction pathway due to the removal of Patched (Ptc). The analysis of target gene expression and morphogenetic read-outs of Hh in embryonic, larval and adult stages indicates that Ci is absolutely required for all examined aspects of Hh outputs. We interpret this as evidence against the existence of Ci-independent branches in the Hh signal transduction pathway and propose that most cases of apparent Ci/Gli-independent Hh output can be attributed to the derepression of target gene expression in the absence of Ci/Gli repressor function.

scholarly journals Differential Expression of the CO2 Fixation Operons of Rhodobacter sphaeroides by the Prr/Reg Two-Component System during Chemoautotrophic Growth

2002 ◽  
Vol 184 (23) ◽  
pp. 6654-6664 ◽  
Author(s):  
Janet L. Gibson ◽  
James M. Dubbs ◽  
F. Robert Tabita
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Cytochrome Oxidase ◽  
Rhodobacter Sphaeroides ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Signal Transduction Pathway ◽  
Pentose Phosphate ◽  
Bisphosphate Carboxylase

ABSTRACT In Rhodobacter sphaeroides, the two cbb operons encoding duplicated Calvin-Benson Bassham (CBB) CO2 fixation reductive pentose phosphate cycle structural genes are differentially controlled. In attempts to define the molecular basis for the differential regulation, the effects of mutations in genes encoding a subunit of Cbb3 cytochrome oxidase, ccoP, and a global response regulator, prrA (regA), were characterized with respect to CO2 fixation (cbb) gene expression by using translational lac fusions to the R. sphaeroides cbb I and cbbII promoters. Inactivation of the ccoP gene resulted in derepression of both promoters during chemoheterotophic growth, where cbb expression is normally repressed; expression was also enhanced over normal levels during phototrophic growth. The prrA mutation effected reduced expression of cbbI and cbbII promoters during chemoheterotrophic growth, whereas intermediate levels of expression were observed in a double ccoP prrA mutant. PrrA and ccoP1 prrA strains cannot grow phototrophically, so it is impossible to examine cbb expression in these backgrounds under this growth mode. In this study, however, we found that PrrA mutants of R. sphaeroides were capable of chemoautotrophic growth, allowing, for the first time, an opportunity to directly examine the requirement of PrrA for cbb gene expression in vivo under growth conditions where the CBB cycle and CO2 fixation are required. Expression from the cbbII promoter was severely reduced in the PrrA mutants during chemoautotrophic growth, whereas cbbI expression was either unaffected or enhanced. Mutations in ccoQ had no effect on expression from either promoter. These observations suggest that the Prr signal transduction pathway is not always directly linked to Cbb3 cytochrome oxidase activity, at least with respect to cbb gene expression. In addition, lac fusions containing various lengths of the cbbI promoter demonstrated distinct sequences involved in positive regulation during photoautotrophic versus chemoautotrophic growth, suggesting that different regulatory proteins may be involved. In Rhodobacter capsulatus, ribulose 1,5-bisphosphate carboxylase-oxygenase (RubisCO) expression was not affected by cco mutations during photoheterotrophic growth, suggesting that differences exist in signal transduction pathways regulating cbb genes in the related organisms.

scholarly journals Mutational analysis of the phototransduction pathway of Chlamydomonas reinhardtii.

1995 ◽  
Vol 131 (2) ◽  
pp. 427-440 ◽  
Author(s):  
G J Pazour ◽  
O A Sineshchekov ◽  
G B Witman
Keyword(s):  
Signal Transduction ◽  
Chlamydomonas Reinhardtii ◽  
Insertional Mutagenesis ◽  
Mutational Analysis ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Normal Manner ◽  
Normal Light ◽  
Phototransduction Pathway

Chlamydomonas has two photobehavioral responses, phototaxis and photoshock. Rhodopsin is the photoreceptor for these responses and the signal transduction process involves transmembrane Ca2+ fluxes. This causes transient changes in flagellar beating, ultimately resulting in phototaxis or photoshock. To identify components that make up this signal transduction pathway, we generated nonphototactic strains by insertional mutagenesis. Seven new phototaxis genes were identified (ptx2-ptx8); alleles of six of these are tagged by the transforming DNA and therefore should be easily cloned. To order the mutants in the pathway, we characterized them electrophysiologically, behaviorally, and structurally, ptx5, ptx6, and ptx7 have normal light-induced photoreceptor currents (PRC) and flagellar currents (FC) but their pattern of swimming does not change in the normal manner when the intraflagellar Ca2+ concentration is decreased, suggesting that they have defects in the ability of their axonemes to respond to changes in Ca2+ concentration. ptx2 and ptx8 lack the FC but have normal PRCs, suggesting that they are defective in the flagellar Ca2+ channel or some factor that regulates it. ptx4 mutants have multiple eye-spots. ptx3 mutants are defective in a component essential for phototaxis but bypassed during photoshock; this component appears to be located downstream of the PRC but upstream of the axoneme.

Signal Transduction Pathway Leading to Hsp27 and Hsp70 Gene Expression during Myocardial Adaptation to Stressa

1998 ◽  
Vol 851 (1 STRESS OF LIF) ◽  
pp. 129-138 ◽  
Author(s):  
DIPAK K. DAS ◽  
NILANJANA MAULIK ◽  
RICHARD M. ENGELMAN ◽  
JOHN A. ROUSOU ◽  
DAVID DEATON ◽  
...  
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Signal Transduction Pathway ◽  
Hsp70 Gene ◽  
Transduction Pathway ◽  
Myocardial Adaptation
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