Fungal Histidine Phosphotransferase Plays a Crucial Role in Photomorphogenesis and Pathogenesis in Magnaporthe oryzae.

Varsha C Mohanan,Johannes Manjrekar,Rajesh N Patkar,Pinal M Chandarana,Bharat B Chattoo

doi:10.3389/fchem.2017.00031

Varsha C Mohanan, Johannes Manjrekar + Show 3 more

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https://doi.org/10.3389/fchem.2017.00031

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Abstract

Two-component signal transduction (TCST) pathways play crucial roles in many cellular functions such as stress responses, biofilm formation, and sporulation. The histidine phosphotransferase (HPt), which is an intermediate phosphotransfer protein in a two-component system, transfers a phosphate group to a phosphorylatable aspartate residue in the target protein(s), and up-regulates stress-activated MAP kinase cascades. Most fungal genomes carry a single copy of the gene coding for HPt, which are potential antifungal targets. However, unlike the histidine kinases (HK) or the downstream response regulators (RR) in two-component system, the HPts have not been well-studied in phytopathogenic fungi. In this study, we investigated the role of HPt in the model rice-blast fungal pathogen Magnaporthe oryzae. We found that in M. oryzae an additional isoform of the HPT gene YPD1 was expressed specifically in response to light. Further, the expression of light-regulated genes such as those encoding envoy and blue-light-harvesting protein, and PAS domain containing HKs was significantly reduced upon down-regulation of YPD1 in M. oryzae. Importantly, down-regulation of YPD1 led to a significant decrease in the ability to penetrate the host cuticle and in light-dependent conidiation in M. oryzae. Thus, our results indicate that Ypd1 plays an important role in asexual development and host invasion, and suggest that YPD1 isoforms likely have distinct roles to play in the rice-blast pathogen M. oryzae.

Highlights

A typical two-component signaling pathway involves a transmembrane histidine kinase (HK), which senses distinct external signal(s)/cue(s) and a response regulator (RR) that activates the downstream mitogen-activated protein (MAP) kinase cascade or directly regulates transcription of the target genes
We identified an ortholog of S. cerevisiae YPD1 in the riceblast fungus (MGG_07173) M. oryzae
Given that photo-illumination is crucial for conidiation or asexual development in M. oryzae, we studied by RT-PCR expression of YPD1 under both dark and light conditions

Summary

Introduction

A typical two-component signaling pathway involves a transmembrane histidine kinase (HK), which senses distinct external signal(s)/cue(s) and a response regulator (RR) that activates the downstream mitogen-activated protein (MAP) kinase cascade or directly regulates transcription of the target genes. In addition to functions in growth and development, TCST pathways are vital determinants of pathogenicity in animal and plant fungal pathogens, such as Candida albicans, Cryptococcus neoformans, A. fumigatus, Cochliobolus heterotrophus, Gibberella zeae, Fusarium oxysporum, B. cinerea, and Alternaria brassicicola (Alex et al, 1998; Clemons et al, 2002; Bahn et al, 2006; Viaud et al, 2006; Cho et al, 2009; Oide et al, 2010; Rispail and Di Pietro, 2010). Genome of the rice-blast fungal pathogen Magnaporthe oryzae has ten HKs, one HPt and three RRs. Like in other fungi, HKs and RRs in M. oryzae have been shown to function in pathways involved in various stress responses, morphogenesis, growth and development (Motoyama et al, 2005a,b, 2008; Zhang et al, 2010; Jacob et al, 2014). HKs Hik and Hik are reported to be important for conidiation and conidial morphology in M. oryzae (Jacob et al, 2014)

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