Ferricrocin, the intracellular siderophore of Trichoderma virens, is involved in growth, conidiation, gliotoxin biosynthesis and induction of systemic resistance in maize

Authors: MUKHERJEE, PRASUN - Texas A&M University; HURLEY, JAMES - Texas A&M University; TAYLOR, JAMES - Texas A&M University; Puckhaber, Lorraine; LEHNER, SYLVIA - University Of Vienna; DRUZHININA, IRINA - University Of Vienna; SCHUMACHER, RAINER - University Of Natural Resources & Applied Life Sciences - Austria; KENERLEY, CHARLES - Texas A&M University

Submitted to: Biochemical and Biophysical Research Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2018
Publication Date: 9/29/2018
Citation: Mukherjee, P.K., Hurley, J.F., Taylor, J.T., Puckhaber, L.S., Lehner, S., Druzhinina, I., Schumacher, R., Kenerley, C.M. 2018. Ferricrocin, the intracellular siderophore of Trichoderma virens, is involved in growth, conidiation, gliotoxin biosynthesis and induction of systemic resistance in maize. Biochemical and Biophysical Research Communications. 505:606-611. https://doi.org/10.1016/j.bbrc.2018.09.170.
DOI: https://doi.org/10.1016/j.bbrc.2018.09.170

Interpretive Summary: Filamentous fungi Trichoderma spp. are important biofungicides and biocontrol agents for enhancing plant resistance by inducing systemic responses. They constitute about 60% of the total biofungicides market. Understanding the mechanisms of microparasitism and the ability to induce systemic resistance in plants by Trichoderma spp. may provide new approaches to seek or develop more effective Trichoderma strains. Ferricrocin is an intracellular compound in filamentous fungi that is known to be involved in iron homeostasis and metabolic processes but its influence on the bioactivity of Trichoderma spp. was unknown. Therefore, mutant strains of T. virens with the ferricrocin production gene deleted were developed and tested for disease control activity on maize inoculated with a foliar pathogen. The lack of ferricrocin enhanced root colonization but reduced the ability of the T. virens to protect the maize from the pathogen. This research indicates that root colonization is only part of Trichoderma bioactivity; adequate nutrient acquisition by the fungus is necessary for exerting protective function to the plant.

Technical Abstract: Fungal siderophores are known to be involved in iron acquisition and storage, as well as pathogenicity of mammals and plants. As avirulent plant symbionts, Trichoderma spp. colonize roots and induce resistance responses both locally and systemically. To study the role of intracellular siderophore(s) in Trichoderma-plant interactions, we have obtained mutants in a non-ribosomal peptide synthetase, TvTex10, that was predicted to be involved in intracellular siderophore(s) biosynthesis. This gene has a detectable basal level of expression and is also upregulated under iron-deplete conditions. This is unlike two other siderophore-encoding genes, which are tightly regulated by iron. Disruption of tex10 gene using homologous recombination resulted in mutants with enhanced growth rate, reduced conidiation and hyper-sensitivity to oxidative stress as compared to wildtype strain. The mutants also produced reduced levels of gliotoxin and dimethyl gliotoxin but have enhanced ability to colonize maize seedling roots. The mutants were also impaired in induction of induced systemic resistance (ISR) in maize against the foliar pathogen Cochliobolus heterostrophus.