Adaptation to pH and Role of PacC in the Rice Blast Fungus Magnaporthe oryzae

Abstract

Fungi are known to adapt to pH partly via specific activation of the Pal signaling pathway and subsequent gene regulation through the transcription factor PacC. The role of PacC in pathogenic fungi has been explored in few species, and each time its partaking in virulence has been found. We studied the impact of pH and the role of PacC in the biology of the rice pathogen Magnaporthe oryzae. Conidia formation and germination were affected by pH whereas fungal growth and appressorium formation were not. Growth in vitro and in planta was characterized by alkalinization and ammonia accumulation in the surrounding medium. Expression of the MoPACC gene increased when the fungus was placed under alkaline conditions. Except for MoPALF, expression of the MoPAL genes encoding the pH-signaling components was not influenced by pH. Deletion of PACC caused a progressive loss in growth rate from pH 5 to pH 8, a loss in conidia production at pH 8 in vitro, a loss in regulation of the MoPALF gene, a decreased production of secreted lytic enzymes and a partial loss in virulence towards barley and rice. PacC therefore plays a significant role in M. oryzae’s biology, and pH is revealed as one component at work during interaction between the fungus and its host plants.

Fungal growth is affected by and affects pH and redox potential (Eh) of the growth medium

“…Sclerotinia) or alkalinize (e.g. Magnaporthe, Botrytis) the media (Landraud et al, 2013;Liu et al, 2017;Vylkova et al, 2017). Changes in Eh were congruent with previous literature, with various aerobes strongly reducing the culture media, due to the consumption of oxygen (Rabotnova & Schwartz, 1962).…”

“…As compared to other microorganisms, fungi are capable of growth and development over wide pH ranges. Several species, including plant pathogens, can actively modulate the pH of their environment by secreting acids or alkali (Landraud et al, 2013;Vylkova et al, 2017). The ability to control extracellular pH is an important aspect of fungal physiology that contributes to fitness within the host (Vylkova et al, 2017) via the modulation of virulence factors to best fit the host (Prusky & Yakoby, 2003).…”

Refining the pH response in Aspergillus nidulans: a modulatory triad involving PacX, a novel zinc binuclear cluster protein

“…Many pacC/RIM101 homologues, like A. nidulans pacC [(Tilburn et al ., ) and Figs and B], are preferentially expressed under neutral to alkaline conditions. These include those of: Beauveria bassiana (Zhou et al ., ), C. albicans (Bensen et al ., ), F. oxysporum (Caracuel et al ., ), Magnaporthe oryzae (Landraud et al ., ), Metarhizium robertsii (Huang et al ., ), Trichoderma harzianum (Moreno‐Mateos et al ., ), T. virens (Trushina et al ., ), Wangiella ( Exophial ) dermatitidis (Wang and Szaniszlo, ), Y. lipolytica (Lambert et al ., ) but not, curiously, S. cerevisiae (Lamb et al ., ; Serrano et al ., ; Lamb and Mitchell, ; Viladevall et al ., ). This suggests that autoregulation might be a common feature, but the absence of reporter studies precludes determining whether this would be positive or negative.…”

Characterization of 47 Cys2‐His2 zinc finger proteins required for the development and pathogenicity of the rice blast fungus Magnaporthe oryzae

“…The C2H2 TF gene COS1 is required for conidiophore development (Zhou et al, 2009). MoPACC, another C2H2 TF gene, is involved in asexual development and pathogenicity via a pH-signaling pathway (Landraud et al, 2013). MST12, an M. oryzae gene that contains both C2H2 and STE domains, is required for invasive growth and pathogenicity (Park et al, 2002).…”