Alfredo Herrera-estrella - Academia.edu (original) (raw)

Papers by Alfredo Herrera-estrella

Developments in Agricultural and Managed Forest Ecology, 1991

Applied and environmental microbiology, 2014

As a result of a transcriptome-wide analysis of the ascomycete Trichoderma atroviride, mycoparasi... more As a result of a transcriptome-wide analysis of the ascomycete Trichoderma atroviride, mycoparasitism-related genes were identified; of these, 13 genes were further investigated for differential expression. In silico analysis of the upstream regulatory regions of these genes pointed to xylanase regulator 1 (Xyr1) as a putatively involved regulatory protein. Transcript analysis of the xyr1 gene of T. atroviride in confrontation with other fungi allowed us to determine that xyr1 levels increased during mycoparasitism. To gain knowledge about the precise role of Xyr1 in the mycoparasitic process, the corresponding gene was deleted from the T. atroviride genome. This resulted in strong reductions in the transcript levels of axe1 and swo1, which encode accessory cell wall-degrading enzymes considered relevant for mycoparasitism. We also analyzed the role of Xyr1 in the Trichoderma-Arabidopsis interaction, finding that the plant response elicited by T. atroviride is delayed if Xyr1 is mis...

Plant molecular biology, 1999

We previously isolated and sequenced the major trypsin inhibitor from Amaranthus hypochonidriacus... more We previously isolated and sequenced the major trypsin inhibitor from Amaranthus hypochonidriacus seeds. This amaranth trypsin inhibitor (AmTI) is a 69 amino acid protein with high homology to members of the potato-1 inhibitor family. This paper describes the cloning and expression of a cDNA encoding this trypsin inhibitor in various vegetative tissues of the amaranth plant during seed development and imbibition, and investigates the possible induction of AmTI expression by wounding. We obtained a 393 bp cDNA sequence with an open reading frame corresponding to a polypeptide with 76 amino acid residues. With the exception of one residue (Ser-41), the polypeptide agrees with the amino acid sequence previously reported, plus 7 more residues at the N-terminus. These N-terminal residues are thought to be part of the signal used for intracellular sorting. The organ specificity of AmTI gene expression was investigated by northern analysis, showing that mRNA corresponding to AmTI genes was...

Journal of bacteriology, 1990

The VirD1 and VirD2 proteins encoded by an inducible locus of the virulence (vir) region of the A... more The VirD1 and VirD2 proteins encoded by an inducible locus of the virulence (vir) region of the Agrobacterium tumefaciens Ti plasmid are required for site-specific nicking at T-DNA border sites. We have determined the nucleotide sequence of a 3.6-kilobase-pair fragment carrying the virD locus from nopaline Ti plasmid pTiC58. In contrast to the previous report (Hagiya et al., Proc. Natl. Acad. Sci. USA 82:2669-2673, 1985), we found that the first three open reading frames were capable of encoding polypeptides of 16.1, 49.7, and 21.4 kilodaltons. Deletion analysis demonstrated that the N-terminal conserved domain of VirD2 was absolutely essential for its endonuclease activity. When extra copies of the virD1 and virD2 genes were present in an A. tumefaciens strain carrying a Ti plasmid, increased amounts of T-strand and nicked molecules could be detected at early stages of vir induction. Such strains possessed the ability to transform plants with higher efficiency.

Annual Review of Phytopathology, 2013

Trichoderma species are widely used in agriculture and industry as biopesticides and sources of e... more Trichoderma species are widely used in agriculture and industry as biopesticides and sources of enzymes, respectively. These fungi reproduce asexually by production of conidia and chlamydospores and in wild habitats by ascospores. Trichoderma species are efficient mycoparasites and prolific producers of secondary metabolites, some of which have clinical importance. However, the ecological or biological significance of this metabolite diversity is sorely lagging behind the chemical significance. Many strains produce elicitors and induce resistance in plants through colonization of roots. Seven species have now been sequenced. Comparison of a primarily saprophytic species with two mycoparasitic species has provided striking contrasts and has established that mycoparasitism is an ancestral trait of this genus. Among the interesting outcomes of genome comparison is the discovery of a vast repertoire of secondary metabolism pathways and of numerous small cysteine-rich secreted proteins. Genomics has also facilitated investigation of sexual crossing in Trichoderma reesei, suggesting the possibility of strain improvement through hybridization.

Frontiers in Plant Science, 2015

Fungi belonging to the genus Trichoderma, commonly found in soil or colonizing plant roots, exert... more Fungi belonging to the genus Trichoderma, commonly found in soil or colonizing plant roots, exert beneficial effects on plants, including the promotion of growth and the induction of resistance to disease. T. virens and T. atroviride secrete the proteins Sm1 and Epl1, respectively, which elicit local and systemic disease resistance in plants. In this work, we show that these fungi promote growth in tomato (Solanum lycopersicum) plants. T. virens was more effective than T. atroviride in promoting biomass gain, and both fungi were capable of inducing systemic protection in tomato against Alternaria solani, Botrytis cinerea, and Pseudomonas syringae pv. tomato (Pst DC3000). Deletion (KO) of epl1 in T. atroviride resulted in diminished systemic protection against A. solani and B. cinerea, whereas the T. virens sm1 KO strain was less effective in protecting tomato against Pst DC3000 and B. cinerea. Importantly, overexpression (OE) of epl1 and sm1 led to an increase in disease resistance against all tested pathogens. Although the Trichoderma WT strains induced both systemic acquired resistance (SAR)- and induced systemic resistance (ISR)-related genes in tomato, inoculation of plants with OE and KO strains revealed that Epl1 and Sm1 play a minor role in the induction of these genes. However, we found that Epl1 and Sm1 induce the expression of a peroxidase and an α-dioxygenase encoding genes, respectively, which could be important for tomato protection by Trichoderma spp. Altogether, these observations indicate that colonization by beneficial and/or infection by pathogenic microorganisms dictates many of the outcomes in plants, which are more complex than previously thought.

Trichoderma: biology and applications, 2013

Journal of Biological Chemistry, 1997

Materials-[␥-32 P]ATP, [␣-32 P]dATP, and [␣-32 P]dCTP (specific radioactivity: 3000 Ci/mmol) were... more Materials-[␥-32 P]ATP, [␣-32 P]dATP, and [␣-32 P]dCTP (specific radioactivity: 3000 Ci/mmol) were purchased from Amersham Corp., Ge-neAmp DNA Amplification kit was from Perkin-Elmer Co. Avicel (PH101, microcrystalline cellulose) was generously provided by Forlab-Kelrio S/A, Brazil.

PLoS ONE, 2014

DNA-photolyases use UV-visible light to repair DNA damage caused by UV radiation. The two major t... more DNA-photolyases use UV-visible light to repair DNA damage caused by UV radiation. The two major types of DNA damage are cyclobutane pyrimidine dimers (CPD) and 6-4 photoproducts (6-4PP), which are repaired under illumination by CPD and 6-4 photolyases, respectively. Cryptochromes are proteins related to DNA photolyases with strongly reduced or lost DNA repair activity, and have been shown to function as blue-light photoreceptors and to play important roles in circadian rhythms in plants and animals. Both photolyases and cryptochromes belong to the cryptochrome/photolyase family, and are widely distributed in all organisms. Here we describe the characterization of cry1, a member of the cryptochrome/ photolyase protein family of the filamentous fungus Trichoderma reesei. We determined that cry1 transcript accumulates when the fungus is exposed to light, and that such accumulation depends on the photoreceptor Blr1 and is modulated by Envoy. Conidia of cry1 mutants show decreased photorepair capacity of DNA damage caused by UV light. In contrast, strains over-expressing Cry1 show increased repair, as compared to the parental strain even in the dark. These observations suggest that Cry1 may be stimulating other systems involved in DNA repair, such as the nucleotide excision repair system. We show that Cry1, heterologously expressed and purified from E. coli, is capable of binding to undamaged and 6-4PP damaged DNA. Photorepair assays in vitro clearly show that Cry1 repairs 6-4PP, but not CPD and Dewar DNA lesions.

Journal of Chemical Ecology, 2014

The conjugates of 6-substituted 1-oxoindanoyl carboxylic acids with L-isoleucine are mimics of th... more The conjugates of 6-substituted 1-oxoindanoyl carboxylic acids with L-isoleucine are mimics of the plant hormone (+)-7-iso-JA-L-Ile (3) that controls and regulates secondary metabolism and stress responses. In order to generate ligands that can be used as hormone-like compounds possessing different biological activities, an efficient and short synthesis of 6-bromo-1-oxoindane-4-carboxylic acid opens a general route to 6-Br-1oxoindanoyl L-isoleucine conjugate (Br-In-L-Ile) (9a) as a key intermediate for several bioactive 6-halogen-In-L-Ile analogs (7a, 8a, 10a). The 6-ethynyl-In-L-Ile analog (11a) might be a valuable tool to localize macromolecular receptor molecules by clickchemistry. The activities of In-Ile derivatives were evaluated by assays inducing the release of volatile organic compounds (VOCs) in lima bean (Phaseolus lunatus). Each compound showed slightly different VOC induction patterns. To correlate such differences with structural features, modeling studies of In-Ile derivatives with COI-JAZa/b/c co-receptors of P. lunatus were performed. The modeling profits from the rigid backbone of the 1-oxoindanonoyl conjugates, which allows only well defined interactions with the receptor complex.

Molecular Microbiology, 2013

The RNAi machinery is generally involved in genome protection in filamentous fungi; however, the ... more The RNAi machinery is generally involved in genome protection in filamentous fungi; however, the physiological role of RNAi has been poorly studied in fungal models. Here, we report that in the filamentous fungus Trichoderma atroviride, the products of the dcr2 and rdr3 genes control reproductive development, because mutations in these genes affect conidiation. In addition, Dcr1 together with Dcr2 control vegetative growth since Δdcr1, Δdcr2 and Δdcr1Δdcr2 present morphological alterations. Whole-genome transcriptional analysis of WT, Δdcr1, Δdcr2 and Δdcr1Δdcr2 show that each Dicer controls different biological processes, such as development or metabolism, which could explain the lack of conidiation in the mutants. Finally, we observed sRNAs that are differentially expressed in the WT and Δdcr2. The expression of some of these sRNAs correlates with the expression of differential transcripts, suggesting that these mRNAs may contain the corresponding targets. Together these data show that in T. atroviride, the RNAi machinery plays a central role in endogenous processes such as development and fitness, beyond controlling genome protection against invasive nucleic acids as reported for other fungi.

Frontiers in Plant Science, 2014

The response to mechanical damage is crucial for the survival of multicellular organisms, enablin... more The response to mechanical damage is crucial for the survival of multicellular organisms, enabling their adaptation to hostile environments. Trichoderma atroviride, a filamentous fungus of great importance in the biological control of plant diseases, responds to mechanical damage by activating regenerative processes and asexual reproduction (conidiation). During this response, reactive oxygen species (ROS) are produced by the NADPH oxidase complex. To understand the underlying early signaling events, we evaluated molecules such as extracellular ATP (eATP) and Ca(2+) that are known to trigger wound-induced responses in plants and animals. Concretely, we investigated the activation of mitogen-activated protein kinase (MAPK) pathways by eATP, Ca(2+), and ROS. Indeed, application of exogenous ATP and Ca(2+) triggered conidiation. Furthermore, eATP promoted the Nox1-dependent production of ROS and activated a MAPK pathway. Mutants in the MAPK-encoding genes tmk1 and tmk3 were affected in wound-induced conidiation, and phosphorylation of both Tmk1 and Tmk3 was triggered by eATP. We conclude that in this fungus, eATP acts as a damage-associated molecular pattern (DAMP). Our data indicate the existence of an eATP receptor and suggest that in fungi, eATP triggers pathways that converge to regulate asexual reproduction genes that are required for injury-induced conidiation. By contrast, Ca(2+) is more likely to act as a downstream second messenger. The early steps of mechanical damage response in T. atroviride share conserved elements with those known from plants and animals.

European Journal of Plant Pathology, 2000

Trichoderma spp. are common soil fungi used as biocontrol agents due to their capacity to produce... more Trichoderma spp. are common soil fungi used as biocontrol agents due to their capacity to produce antibiotics, induce systemic resistance in plants and parasitize phytopathogenic fungi of major agricultural importance. The present study investigated whether colonization of Arabidopsis thaliana seedlings by Trichoderma atroviride affected plant growth and development. Here it is shown that T. atroviride promotes growth in Arabidopsis. Moreover,