Transcriptome Reprogramming of Tomato Orchestrate the Hormone Signaling Network of Systemic Resistance Induced by Chaetomium globosum.

Jagmohan Singh,Amolkumar U Solanke,Rashmi Aggarwal,K Darshan,Zakir Hussain,Bishnu Maya Bashyal,M S Saharan,Pooja Parmar

doi:10.3389/fpls.2021.721193

Abstract

Chaetomium globosum is a potential biological control agent effective against various plant pathogens. Several reports are available on the mycoparastism and antibiosis mechanisms of C. globosum against plant pathogenic fungi, whereas a few states induced resistance. The potential induced defense component of C. globosum (Cg-2) was evaluated against early blight disease of tomato (Solanum lycopersicum) and further, global RNA sequencing was performed to gain deep insight into its mechanism. The expression of marker genes of hormone signaling pathways, such as PR1, PiII, PS, PAL, Le4, and GluB were analyzed using real-time quantitative reverse transcription PCR (qRT-PCR) to determine the best time point for RNA sequencing. The transcriptome data revealed that 22,473 differentially expressed genes (DEGs) were expressed in tomato at 12 h post Cg-2 inoculation as compared with control plants and among these 922 DEGs had a fold change of −2 to +2 with p < 0.05. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that most of the DEGs were belonging to metabolic pathways, biosynthesis of secondary metabolites, plant–pathogen interaction, chlorophyll metabolism, and plant hormone signal transduction. Gene Ontology (GO) analysis revealed that DEGs were enriched mainly related to binding activity (GO:0005488), catalytic activity (GO:0003824), metabolic process (GO:0008152), cellular process (GO:0009987), response to stimulus (GO:0050896), biological regulation (GO:0065007), and transcription regulator activity (GO:0140110). The gene modulations in hormone signaling transduction, phenylpropanoid biosynthesis, and mitogen-activated protein kinases (MPK) signaling indicated the upregulation of genes in these pathways. The results revealed active participation of jasmonic acid (JA) and salicylic acid (SA) signaling transduction pathways which further indicated the involvement of induced systemic resistance (ISR) and systemic acquired resistance (SAR) in the systemic resistance induced by Cg-2 in tomato.

Highlights

Chaetomium globosum is an important biocontrol agent reported to be effective against a number of soil, seed, and airborne fungal diseases in plants, such as spot blotch of wheat, rice blast, root rot of citrus, potato dry rot, and late blight of potato (Aggarwal et al, 2004; Park et al, 2005; Shanthiyaa et al, 2013; Quyet et al, 2016; Jiang et al, 2017)
The plant growth parameters were statistically significantly different when treated with biocontrol agent Cg-2 and were analyzed by Student’s t-test with SPSS
The comparative results for stomatal conductance (t = −5.55, p = 0.00, α = 0.05, i.e., p < α) and transpiration rate (t = −7.90, p = 0.00, α = 0.05, i.e., p < α) for biocontrol treated vs. untreated plants showed statistically significant difference, whereas the photosynthesis rate did not show statistically significant difference (t = −1.11, p = 0.28, α = 0.05, i.e., p> α)

Summary

Introduction

Chaetomium globosum is an important biocontrol agent reported to be effective against a number of soil, seed, and airborne fungal diseases in plants, such as spot blotch of wheat, rice blast, root rot of citrus, potato dry rot, and late blight of potato (Aggarwal et al, 2004; Park et al, 2005; Shanthiyaa et al, 2013; Quyet et al, 2016; Jiang et al, 2017). The antagonistic mechanisms of C. globosum comprise of competition for space and nutrients, mycoparasitism, and metabolite production (antibiosis), such as prenisatin, chaetoglobosin, chaetocin, cochliodinol, and chaetomin (Brewer et al, 1972; Brewer and Taylor, 1978; Vannacci and Harman, 1987; Soytong, 1992). Antibiosis and mycoparasitism have been observed against various fungal pathogens, such as Bipolaris sorokiniana, Setosphaeria turcica, and Phytophthora palmivora (Aggarwal et al, 2011; Zhang et al, 2013; Hung et al, 2015). Under in vitro conditions C. globosum inhibits the mycelial growth of Puccinia triticina and Bipolaris sorokiniana in wheat (Aggarwal et al, 2016). A plethora of information is available on mycoparasitism and antibiosis as a biocontrol mechanism of C. globosum, whereas the induced resistance component is least explored (Aggarwal, 2015)

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