Biomedical subjects

Gopal Iyer

Publications and source records attributed to Gopal Iyer.

5 recordsLinked to original sources

PubMed2006

VIB-1 is required for expression of genes necessary for programmed cell death in Neurospora crassa.

Nonself recognition during somatic growth is an essential and ubiquitous phenomenon in both prokaryotic and eukaryotic species. In filamentous fungi, nonself recognition is also important during vegetative growth. Hyphal fusion between genetically dissimilar individuals results in rejection of heterokaryon formation and in programmed cell death of the fusion compartment. In filamentous fungi, such as Neurospora crassa, nonself recognition and heterokaryon incompatibility (HI) are regulated by genetic differences at het loci. In N. crassa, mutations at the vib-1 locus suppress nonself recognition and HI mediated by genetic differences at het-c/pin-c, mat, and un-24/het-6. vib-1 is a homolog of Saccharomyces cerevisiae NDT80, which is a transcriptional activator of genes during meiosis. For this study, we determined that vib-1 encodes a nuclear protein and showed that VIB-1 localization varies during asexual reproduction and during HI. vib-1 is required for the expression of genes involved in nonself recognition and HI, including pin-c, tol, and het-6; all of these genes encode proteins containing a HET domain. vib-1 is also required for the production of downstream effectors associated with HI, including the production of extracellular proteases upon carbon and nitrogen starvation. Our data support a model in which mechanisms associated with starvation and nonself recognition/HI are interconnected. VIB-1 is a major regulator of responses to nitrogen and carbon starvation and is essential for the expression of genes involved in nonself recognition and death in N. crassa.

Apoptosis↗

PubMed2006

Peptide coated quantum dots for biological applications.

Quantum dots (QDOTs) have been widely recognized by the scientific community and the biotechnology industry, as witnessed by the exponential growth of this field in the past several years. We describe the synthesis and characterization of visible and near infrared QDots--a critical step for engineering organic molecules like proteins and peptides for building nanocomposite materials with multifunctional properties suitable for biological applications.

Coated Materials, Biocompatible↗

PubMed2005

Advances in fluorescence imaging with quantum dot bio-probes.

After much effort in surface chemistry development and optimization by several groups, fluorescent semiconductor nanocrystals probes, also known as quantum dots or qdots, are now entering the realm of biological applications with much to offer to biologists. The road to success has been paved with hurdles but from these efforts has stemmed a multitude of original surface chemistries that scientists in the biological fields can draw from for their specific biological applications. The ability to easily modulate the chemical nature of qdot surfaces by employing one or more of the recently developed qdot coatings, together with their exceptional photophysics have been key elements for qdots to acquire a status of revolutionary fluorescent bio-probes. Indeed, the unique properties of qdots not only give biologists the opportunity to explore advanced imaging techniques such as single molecule or lifetime imaging but also to revisit traditional fluorescence imaging methodologies and extract yet unobserved or inaccessible information in vitro or in vivo.

Chromogenic Compounds↗

PubMed2003

Purification and characterization of laccase from the rice blast fungus, Magnaporthe grisea.

A 70-kDa extracellular laccase was purified from the rice blast fungus Magnaporthe grisea using gel filtration and ion exchange chromatography The procedure provided 282-fold purification with a specific enzyme activity of 225.91 U mg(-1) and a yield of 11.92%. The enzyme oxidized a wide range of substrates. The highest level of oxidation was detected with syringaldazine as the substrate. Using syringaldazine as the substrate, the enzyme exhibited a pH optimum of 6 and temperature optimum of 30 degrees C, and its K(m) was 0.118 mM. The enzyme was strongly inhibited by Cu-chelating agents.

Chromatography, High Pressure Liquid↗

PubMed2002

Nonself recognition is mediated by HET-C heterocomplex formation during vegetative incompatibility.

Nonself recognition during vegetative growth in filamentous fungi is mediated by heterokaryon incompatibility (het) loci. In Neurospora crassa, het-c is one of 11 het loci. Three allelic specificity groups, termed het-c(OR), het-c(PA) and het-c(GR), exist in natural populations. Heterokaryons or partial diploids that contain het-c alleles of alternative specificity show severe growth inhibition, repression of conidiation and hyphal compartmentation and death (HCD). Using epitope-tagged HET-C, we show that nonself recognition is mediated by the presence of a heterocomplex composed of polypeptides encoded by het-c alleles of alternative specificity. The HET-C heterocomplex localized to the plasma membrane (PM); PM-bound HET-C heterocomplexes occurred in all three het-c incompatible allelic interactions. Strains containing het-c constructs deleted for a predicted signal peptide sequence formed HET-C heterocomplexes in the cytoplasm and showed a growth arrest phenotype. Our finding is a step towards understanding nonself recognition mechanisms that operate during vegetative growth in filamentous fungi, and provides a model for investigating relationships between recognition mechanisms and cell death.

Alleles↗