scholarly journals Functional Characterization of fst1 in Fusarium verticillioides During Colonization of Maize Kernels

2011 ◽  
Vol 24 (1) ◽  
pp. 18-24 ◽  
Author(s):  
Hun Kim ◽  
Charles P. Woloshuk
Keyword(s):  
Fusarium Verticillioides ◽  
Functional Characterization ◽  
Hexose Transporter ◽  
Maize Endosperm ◽  
Endosperm Tissue ◽  
Genes Expression ◽  
Fluorescent Tag ◽  
Maize Kernels ◽  
Delayed Growth

The putative hexose transporter gene fst1 in Fusarium verticillioides was identified previously by microarray analysis as a gene that was more highly expressed during colonization of autoclaved maize endosperm than germ. In contrast to a previous study, in which disruption of fst1 did not affect growth of the pathogen on autoclaved maize kernels, in the current study, we demonstrated that disruption of fst1 delayed growth and symptom development on wounded maize ears. Characterization of the fst1 promoter revealed that regulation of fst1 expression was similar to that of fumonisin biosynthetic (fum) genes; expression was highest during growth on endosperm tissue and repressed by elevated concentrations of ammonium in the growth medium. With a fluorescent tag attached to FST1, the protein localized transiently to the periphery of the cells near the plasma membrane and in vacuole-like structures, suggesting that membrane-localized FST1 was internalized and degraded in vacuoles. Expression of fst1 in a yeast strain lacking hexose transporter genes did not complement the yeast mutation, suggesting that FST1 does not transport glucose, fructose, or mannose. The results indicate a functional role for FST1 in pathogenesis during the colonization of living kernels.

Functional characterization of the hexose transporter Hxt13p: An efflux pump that mediates resistance to miltefosine in yeast

2013 ◽  
Vol 61 ◽  
pp. 23-32 ◽  
Author(s):  
Chayanika Biswas ◽  
Julianne T. Djordjevic ◽  
Xiaoming Zuo ◽  
Eckhard Boles ◽  
Katrina A. Jolliffe ◽  
...  
Keyword(s):  
Efflux Pump ◽  
Functional Characterization ◽  
Hexose Transporter

scholarly journals TworsaMhomologues encode central regulatory elements modulating quorum sensing expression inBurkholderia thailandensis

2017 ◽  
Author(s):  
Servane Le Guillouzer ◽  
Marie-Christine Groleau ◽  
Eric Déziel
Keyword(s):  
Quorum Sensing ◽  
Functional Characterization ◽  
Gene Clusters ◽  
Homoserine Lactone ◽  
Regulatory Elements ◽  
Burkholderia Thailandensis ◽  
Gene Coding ◽  
Genes Expression ◽  
In The Wild

AbstractThe bacteriumBurkholderia thailandensispossesses three conservedN-acyl-L-homoserine lactone (AHL) quorum sensing (QS) systems designated BtaI1/BtaR1 (QS-1), BtaI2/BtaR2 (QS-2), and BtaI3/BtaR3 (QS-3). These QS-systems are associated with the biosynthesis ofN-octanoyl-homoserine lactone (C8-HSL),N-3-hydroxy-decanoyl-homoserine lactone (3OHC10-HSL), as well asN-3-hydroxy-octanoyl-homoserine lactone (3OHC8-HSL), which are produced by the LuxI-type synthase BtaI1, BtaI2, and BtaI3, and modulated by the LuxR-type transcriptional regulators BtaR1, BtaR2, and BtaR3. BothbtaR1/btaI1andbtaR2/btaI2gene clusters contain an additional gene that is conserved in theBurkholderiagenus, homologous to a gene coding for the negative AHL biosynthesis modulatory protein RsaM originally identified in the phytopathogenPseudomonas fuscovaginae, and hence designatedrsaM1andrsaM2. We have characterized the function of these tworsaMhomologues and demonstrated their involvement in the regulation of AHLs biosynthesis inB. thailandensisstrain E264. We measured the production of C8-HSL, 3OHC10-HSL, and 3OHC8-HSL by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in the wild-type strain and in thersaM1-andrsaM2-mutants, and monitored the transcription ofbtaI1,btaI2, andbtaI3 using chromosomal mini-CTX-luxtranscriptional reporters. The expression ofbtaR1,btaR2, andbtaR3 was also measured by quantitative everse-transcription PCR (qRT-PCR). We demonstrate that the QS-1 system is repressed by RsaM1, whereas RsaM2 principally represses the QS-2 system. We also found that bothrsaM1andrsaM2are QS-controlled, as well as negatively auto-regulated. We conclude that RsaM1 and RsaM2 are an integral part of the QS modulatory circuitry ofB. thailandensis, and play a major role in the hierarchical and homeostatic organization of the QS-1, QS-2, and QS-3 systems.ImportanceQuorum sensing (QS) is a global regulatory mechanism of genes expression depending on bacterial density. QS is commonly involved in the coordination of genes expression associated with the establishment of host-pathogen interactions and acclimatization to the environment. We present the functional characterization of the tworsaMhomologues designatedrsaM1andrsaM2in the regulation of the multiple QS systems coexisting in the non-pathogenic bacteriumBurkholderia thailandensis, widely used as a model system for the study of the pathogenBurkholderia pseudomallei. We found that inactivation of thesersaMhomologues, which are clustered with the other QS genes, profoundly affects the QS regulatory circuity ofB. thailandensis. It is proposed that these genes code for QS repressors and we conclude that they constitute essential regulatory components of the QS modulatory network ofB. thailandensis, and provide additional layers of regulation to modulate the expression of QS-controlled genes, including those encoding virulence/survival factors and linked to environmental adaptation inB. pseudomallei.

scholarly journals ADP-glucose drives starch synthesis in isolated maize endosperm amyloplasts: characterization of starch synthesis and transport properties across the amyloplast envelope

1997 ◽  
Vol 324 (2) ◽  
pp. 503-509 ◽  
Author(s):  
Torsten MÖHLMANN ◽  
Joachim TJADEN ◽  
Gundrun HENRICHS ◽  
Paul W. QUICK ◽  
Rainer HÄUSLER ◽  
...  
Keyword(s):  
Starch Synthesis ◽  
Dihydroxyacetone Phosphate ◽  
Maize Endosperm ◽  
Endosperm Tissue ◽  
Plastid Envelope ◽  
Phosphorylated Compounds ◽  
Saturation Kinetics ◽  
Uptake Data ◽  
Hexose Phosphates

We recently developed a method of purifying amyloplasts from developing maize (Zea mays L.) endosperm tissue [Neuhaus, Thom, Batz and Scheibe (1993) Biochem. J. 296, 395–401]. In the present paper we analyse how glucose 6-phosphate (Glc6P) and other phosphorylated compounds enter the plastid compartment. Using a proteoliposome system in which the plastid envelope membrane proteins are functionally reconstituted, we demonstrate that this type of plastid is able to transport [14C]Glc6P or [32P]Pi in counter exchange with Pi, Glc6P, dihydroxyacetone phosphate and phosphoenolpyruvate. Glucose 1-phosphate, fructose 6-phosphate and ribose 5-phosphate do not act as substrates for counter exchange. Besides hexose phosphates, ADP-glucose (ADPGlc) also acts as a substrate for starch synthesis in isolated maize endosperm amyloplasts. This process exhibits saturation kinetics with increasing concentrations of exogenously supplied [14C]ADPGlc, reaching a maximum at 2 mM. Ultrasonication of isolated amyloplasts greatly reduces the rate of ADPGlc-dependent starch synthesis, indicating that the process is dependent on the intactness of the organelles. The plastid ATP/ADP transporter is not responsible for ADPGlc uptake. Data are presented that indicate that ADPGlc is transported by another translocator in counter exchange with AMP. To analyse the physiology of starch synthesis in more detail, we examined how Glc6P- and ADPGlc-dependent starch synthesis in isolated maize endosperm amyloplasts interact. Glc6P-dependent starch synthesis is not inhibited by increasing concentrations of ADPGlc. In contrast, the rate of ADPGlc-dependent starch synthesis is reduced by increasing concentrations of ATP necessary for Glc6P-dependent starch synthesis. The possible modes of inhibition of ADPGlc-dependent starch synthesis by ATP are discussed with respect to the stromal generation of AMP required for ADPGlc uptake.

scholarly journals Functional Characterization of a Hexose Transporter from Root Endophyte Piriformospora indica

2016 ◽  
Vol 7 ◽  
Author(s):  
Mamta Rani ◽  
Sumit Raj ◽  
Vikram Dayaman ◽  
Manoj Kumar ◽  
Meenakshi Dua ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Piriformospora Indica ◽  
Hexose Transporter ◽  
Root Endophyte

Functional characterization of human brown adipose tissue metabolism

2020 ◽  
Vol 477 (7) ◽  
pp. 1261-1286 ◽  
Author(s):  
Marie Anne Richard ◽  
Hannah Pallubinsky ◽  
Denis P. Blondin
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Functional Characterization ◽  
Human Infants ◽  
Positron Emission ◽  
Brown Adipose ◽  
Treatment Of Obesity ◽  
And Function

Brown adipose tissue (BAT) has long been described according to its histological features as a multilocular, lipid-containing tissue, light brown in color, that is also responsive to the cold and found especially in hibernating mammals and human infants. Its presence in both hibernators and human infants, combined with its function as a heat-generating organ, raised many questions about its role in humans. Early characterizations of the tissue in humans focused on its progressive atrophy with age and its apparent importance for cold-exposed workers. However, the use of positron emission tomography (PET) with the glucose tracer [18F]fluorodeoxyglucose ([18F]FDG) made it possible to begin characterizing the possible function of BAT in adult humans, and whether it could play a role in the prevention or treatment of obesity and type 2 diabetes (T2D). This review focuses on the in vivo functional characterization of human BAT, the methodological approaches applied to examine these features and addresses critical gaps that remain in moving the field forward. Specifically, we describe the anatomical and biomolecular features of human BAT, the modalities and applications of non-invasive tools such as PET and magnetic resonance imaging coupled with spectroscopy (MRI/MRS) to study BAT morphology and function in vivo, and finally describe the functional characteristics of human BAT that have only been possible through the development and application of such tools.

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