Early Transcriptome Response of Trichoderma virens to Colonization of Maize Roots.

James T Taylor,Ken-Der Wang,Charles M Kenerley,Benjamin Horwitz,Michael Kolomiets

doi:10.3389/ffunb.2021.718557

Abstract

Trichoderma virens is a well-known mycoparasitic fungal symbiont that is valued for its biocontrol capabilities. T. virens initiates a symbiotic relationship with a plant host through the colonization of its roots. To achieve colonization, the fungus must communicate with the host and evade its innate defenses. In this study, we explored the genes involved with the host communication and colonization process through transcriptomic profiling of the wild-type fungus and selected deletion mutants as they colonized maize roots. Transcriptome profiles of the T. virens colonization of maize roots over time revealed that 24 h post inoculation appeared to be a key time for plant-microbe communication, with many key gene categories, including signal transduction mechanisms and carbohydrate transport and metabolism, peaking in expression at this early colonization time point. The transcriptomic profiles of Sm1 and Sir1 deletion mutants in the presence of plants demonstrated that Sir1, rather than Sm1, appears to be the key regulator of the fungal response to maize, with 64% more unique differentially expressed genes compared to Sm1. Additionally, we developed a novel algorithm utilizing gene clustering and coexpression network analyses to select potential colonization-related gene targets for characterization. About 40% of the genes identified by the algorithm would have been missed using previous methods for selecting gene targets.

Highlights

The rhizospheric fungus Trichoderma virens is well-known for its role as a plant symbiont that protects its host from pathogenic attack directly through mycoparasitism and indirectly through the induction of plant systemic defenses (Howell, 1987; Djonovicet al., 2006a,b, 2007; Kubicek et al, 2011; Nawrocka and Małolepsza, 2013; Guzmán-Guzmán et al, 2017)
We developed a novel target enrichment pipeline that uses gene co-expression networks to select gene targets with higher likelihood of functional relevance to the interaction between the fungus and the plant and analyzed a previously sequenced transcriptomic dataset of the T. virens mutants Sm1 and Sir1 to compare to the transcriptome changes found in wild-type strain
We concluded that 12 hpi was a transitionary period in the colonization process, and 15 hpi represented the time of full ingress of the root in our system

Summary

Introduction

The rhizospheric fungus Trichoderma virens is well-known for its role as a plant symbiont that protects its host from pathogenic attack directly through mycoparasitism and indirectly through the induction of plant systemic defenses (Howell, 1987; Djonovicet al., 2006a,b, 2007; Kubicek et al, 2011; Nawrocka and Małolepsza, 2013; Guzmán-Guzmán et al, 2017). This symbiotic relationship is perceived to be the result of fungal root colonization and communication with the host.

Methods

Results

Conclusion