Biomedical subjects

Sergio Casas-Flores

Publications and source records attributed to Sergio Casas-Flores.

4 recordsLinked to original sources

PubMed2026

Endophytic fungi isolated from coffee plants promote Arabidopsis thaliana growth and suppress soil-borne fungal pathogens.

Endophytic beneficial microorganisms are widely used in agriculture for promoting plant growth and enhancing plant defense mechanisms. This study aimed to characterize endophytic fungi isolated from the roots of coffee plants cultivated in organic agroforestry systems and evaluate their potential as biocontrol agents against fungal pathogens, as well as their ability to promote plant growth. Biocontrol activity was assessed using in vitro dual-culture assays on potato dextrose agar, measuring the inhibition of pathogen growth. Plant growth promotion was evaluated by co-cultivating Arabidopsis thaliana seedlings with fungal isolates on Murashige and Skoog medium. Isolates were further subjected to both qualitative and quantitative biochemical characterization. A total of 18 endophytic fungal strains were identified and classified in five genera: Colletotrichum, Fusarium, Simplicillium, Lasiodiplodia and Trichoderma. Among these, ten Trichoderma isolates demonstrated strong antagonistic activity against selected fungal pathogens and significantly enhanced the growth of Arabidopsis seedlings in vitro. These beneficial effects were associated with the production of siderophores and indole-3-acetic acid, as well as the apparent nitrogen availability -- likely mediated through interactions with nitrogen-fixing bacteria.

Arabidopsis↗

PubMed2006

Cross talk between a fungal blue-light perception system and the cyclic AMP signaling pathway.

Blue light regulates many physiological and developmental processes in fungi. In Trichoderma atroviride the complex formed by the BLR-1 and BLR-2 proteins appears to play an essential role as a sensor and transcriptional regulator in photoconidiation. Here we demonstrate that the BLR proteins are necessary for carbon deprivation induced conidiation, even in the absence of light, pointing to the existence of an unprecedented cross talk between light and carbon sensing. Further, in contrast to what has been found in all other fungal systems, clear BLR-independent blue-light responses, including the activation of protein kinase A (PKA) and the regulation of gene expression, were found. Expression of an antisense version of the pkr-1 gene, encoding the regulatory subunit of PKA, resulted in a nonsporulating phenotype, whereas overexpression of the gene produced colonies that conidiate even in the dark. In addition, overexpression of pkr-1 blocked the induction of early light response genes. Thus, our data demonstrate that PKA plays an important role in the regulation of light responses in Trichoderma. Together, these observations suggest that the BLR complex plays a general role in sensing environmental cues that trigger conidiation and that such a role can be separated from its function as a transcription factor.

Cyclic AMP↗

PubMed2004

BLR-1 and BLR-2, key regulatory elements of photoconidiation and mycelial growth in Trichoderma atroviride.

In fungi, phototropism, the induction of carotenogenesis and reproductive structures, and resetting of the circadian rhythm are controlled by blue light. Trichoderma atroviride, a fungus used in biological control, sporulates in a synchronized manner following a brief pulse of blue light. Due to its apparent simplicity, this response was chosen for pursuing photoreceptor isolation. Two genes were cloned, blue-light regulators 1 and 2 (blr-1 and blr-2), similar to the Neurospora crassa white-collar 1 and 2, respectively. The BLR-1 protein has all the characteristics of a blue-light photoreceptor, whereas the structure of the deduced BLR-2 protein suggests that it interacts with BLR-1 through PAS domains to form a complex. Disruption of the corresponding genes demonstrated that they are essential for blue-light-induced conidiation. blr-1 and blr-2 were also shown to be essential for the light-induced expression of the photolyase-encoding gene (phr-1). Mechanical injury of mycelia was found to trigger conidiation of T. atroviride, a response not described previously. This response was not altered in the mutants. A novel effect of both red and blue light on mycelial growth was found involving another light receptor, which is compensated by the BLR proteins.

Amino Acid Sequence↗

PubMed2004

Three decades of fungal transformation: novel technologies.

Fungi are lower eukaryotes that play important roles in many human activities, including biotechnological processes, phytopathology, and biomedical research. In addition, they are excellent models for molecular and genetic studies. An important key in the advancement of genetics and molecular biology of a given organism is the development of genetic transformation systems. This technology makes possible the analysis and manipulation of the genome of the organism of interest. Thirty years from the first report of transformation of a fungus, transformation of many other fungi has been achieved. However, the development of gene tagging systems generally applicable to a wide range of filamentous fungi has remained elusive. A widely used gene tagging strategy for filamentous fungi is restriction enzyme mediated integration (REMI). In recent years numerous reports have been published describing the effective application of REMI. However, REMI shows certain disadvantages for some fungi. Recently a very promising alternative strategy has been reported based on the use of the soil bacterium Agrobacterium tumefaciens. Using this system a well-defined DNA segment (T-DNA) is transferred, which integrates by illegitimate recombination and is 100-1000 times more efficient than conventional methods. The T-DNA can be used as an efficient tool to generate recombinant strains where DNA is integrated as a single copy, allowing the generation of collections of gene-tagged mutants of the fungus of interest.

Agrobacterium tumefaciens↗