Browsing by Author "Martinez, Diego"

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    Attention-driven reaction to extreme earnings surprises
    (2023) Reyes, Tomas; Batista, Julian A.; Chacon, Alvaro; Martinez, Diego; Kausel, Edgar E.
    We investigate the relationship between investor attention and stock returns in the context of extreme earnings surprises. We propose a novel mechanism that describes this interaction: high attention to very positive and very negative earnings news results in faster incorporation of information into stock prices, an overreaction effect, and a subsequent partial reversal. We test this mechanism using post-announcement abnormal returns and measure investor attention using internet search volume. We confirm that abnormal attention to earnings announcements is positively related to post-announcement abnormal returns when earnings surprises are very positive and negatively related when earnings surprises are very negative. More importantly, we argue that investors exhibit attention-driven overreactions to these extreme earnings surprises since the initial effects of abnormal attention on abnormal returns are subsequently partially reversed.
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    Genome sequencing and analysis of the biomass-degrading fungus Trichoderma reesei (syn. Hypocrea jecorina)
    (2008) Martinez, Diego; Berka, Randy M.; Henrissat, Bernard; Saloheimo, Markku; Arvas, Mikko; Baker, Scott E.; Chapman, Jarod; Chertkov, Olga; Coutinho, Pedro M.; Cullen, Dan; Danchin, Etienne G. J.; Grigoriev, Igor V.; Harris, Paul; Jackson, Melissa; Kubicek, Christian P.; Han, Cliff S.; Ho, Isaac; Larrondo, Luis F.; de Leon, Alfredo Lopez; Magnuson, Jon K.; Merino, Sandy; Misra, Monica; Nelson, Beth; Putnam, Nicholas; Robbertse, Barbara; Salamov, Asaf A.; Schmoll, Monika; Terry, Astrid; Thayer, Nina; Westerholm-Parvinen, Ann; Schoch, Conrad L.; Yao, Jian; Barbote, Ravi; Nelson, Mary Anne; Detter, Chris; Bruce, David; Kuske, Cheryl R.; Xie, Gary; Richardson, Paul; Rokhsar, Daniel S.; Lucas, Susan M.; Rubin, Edward M.; Dunn-Coleman, Nigel; Ward, Michael; Brettin, Thomas S.
    Trichoderma reesei is the main industrial source of cellulases and hemicellulases used to depolymerize biomass to simple sugars that are converted to chemical intermediates and biofuels, such as ethanol. We assembled 89 scaffolds (sets of ordered and oriented contigs) to generate 34 Mbp of nearly contiguous T. reesei genome sequence comprising 9,129 predicted gene models. Unexpectedly, considering the industrial utility and effectiveness of the carbohydrate-active enzymes of T. reesei, its genome encodes fewer cellulases and hemicellulases than any other sequenced fungus able to hydrolyze plant cell wall polysaccharides. Many T. reesei genes encoding carbohydrate-active enzymes are distributed nonrandomly in clusters that lie between regions of synteny with other Sordariomycetes. Numerous genes encoding biosynthetic pathways for secondary metabolites may promote survival of T. reesei in its competitive soil habitat, but genome analysis provided little mechanistic insight into its extraordinary capacity for protein secretion. Our analysis, coupled with the genome sequence data, provides a roadmap for constructing enhanced T. reesei strains for industrial applications such as biofuel production.
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    Genome, transcriptome, and secretome analysis of wood decay fungus Postia placenta supports unique mechanisms of lignocellulose conversion
    (2009) Martinez, Diego; Challacombe, Jean; Morgenstern, Ingo; Hibbett, David; Schmoll, Monika; Kubicek, Christian P.; Ferreira, Patricia; Ruiz-Duenas, Francisco J.; Martinez, Angel T.; Kersten, Phil; Hammel, Kenneth E.; Wymelenberg, Amber Vanden; Gaskell, Jill; Lindquist, Erika; Sabat, Grzegorz; BonDurant, Sandra Splinter; Larrondo, Luis F.; Canessa, Paulo; Vicuna, Rafael; Yadav, Jagjit; Doddapaneni, Harshavardhan; Subramanian, Venkataramanan; Pisabarro, Antonio G.; Lavin, Jose L.; Oguiza, Jose A.; Master, Emma; Henrissat, Bernard; Coutinho, Pedro M.; Harris, Paul; Magnuson, Jon Karl; Baker, Scott E.; Bruno, Kenneth; Kenealy, William; Hoegger, Patrik J.; Kuees, Ursula; Ramaiya, Preethi; Lucash, Susan; Salamov, Asaf; Shapiro, Harris; Tu, Hank; Chee, Christine L.; Misra, Monica; Xie, Gary; Teter, Sarah; Yaver, Debbie; James, Tim; Mokrejs, Martin; Pospisek, Martin; Grigoriev, Igor V.; Brettin, Thomas; Rokhsar, Dan; Berka, Randy; Cullen, Dan
    Brown-rot fungi such as Postia placenta are common inhabitants of forest ecosystems and are also largely responsible for the destructive decay of wooden structures. Rapid depolymerization of cellulose is a distinguishing feature of brown-rot, but the biochemical mechanisms and underlying genetics are poorly understood. Systematic examination of the P. placenta genome, transcriptome, and secretome revealed unique extracellular enzyme systems, including an unusual repertoire of extracellular glycoside hydrolases. Genes encoding exo-cellobiohydrolases and cellulose-binding domains, typical of cellulolytic microbes, are absent in this efficient cellulose-degrading fungus. When P. placenta was grown in medium containing cellulose as sole carbon source, transcripts corresponding to many hemicellulases and to a single putative beta-1-4 endoglucanase were expressed at high levels relative to glucose-grown cultures. These transcript profiles were confirmed by direct identification of peptides by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Also up-regulated during growth on cellulose medium were putative iron reductases, quinone reductase, and structurally divergent oxidases potentially involved in extracellular generation of Fe(II) and H2O2. These observations are consistent with a biodegradative role for Fenton chemistry in which Fe( II) and H2O2 react to form hydroxyl radicals, highly reactive oxidants capable of depolymerizing cellulose. The P. placenta genome resources provide unparalleled opportunities for investigating such unusual mechanisms of cellulose conversion. More broadly, the genome offers insight into the diversification of lignocellulose degrading mechanisms in fungi. Comparisons with the closely related white-rot fungus Phanerochaete chrysosporium support an evolutionary shift from white-rot to brown-rot during which the capacity for efficient depolymerization of lignin was lost.