The bZIP Transcription Factor MoAP1 Mediates the Oxidative Stress Response and Is Critical for Pathogenicity of the Rice Blast Fungus Magnaporthe oryzae

Abstract

Saccharomyces cerevisiae Yap1 protein is an AP1-like transcription factor involved in the regulation of the oxidative stress response. An ortholog of Yap1, MoAP1, was recently identified from the rice blast fungus Magnaporthe oryzae genome. We found that MoAP1 is highly expressed in conidia and during invasive hyphal growth. The Moap1 mutant was sensitive to H2O2, similar to S. cerevisiae yap1 mutants, and MoAP1 complemented Yap1 function in resistance to H2O2, albeit partially. The Moap1 mutant also exhibited various defects in aerial hyphal growth, mycelial branching, conidia formation, the production of extracellular peroxidases and laccases, and melanin pigmentation. Consequently, the Moap1 mutant was unable to infect the host plant. The MoAP1-eGFP fusion protein is localized inside the nucleus upon exposure to H2O2, suggesting that MoAP1 also functions as a redox sensor. Moreover, through RNA sequence analysis, many MoAP1-regulated genes were identified, including several novel ones that were also involved in pathogenicity. Disruption of respective MGG_01662 (MoAAT) and MGG_02531 (encoding hypothetical protein) genes did not result in any detectable changes in conidial germination and appressorium formation but reduced pathogenicity, whereas the mutant strains of MGG_01230 (MoSSADH) and MGG_15157 (MoACT) showed marketed reductions in aerial hyphal growth, mycelial branching, and loss of conidiation as well as pathogenicity, similar to the Moap1 mutant. Taken together, our studies identify MoAP1 as a positive transcription factor that regulates transcriptions of MGG_01662, MGG_02531, MGG_01230, and MGG_15157 that are important in the growth, development, and pathogenicity of M. oryzae.

Basic Leucine Zipper (bZIP) Domain Transcription Factor MBZ1 Regulates Cell Wall Integrity, Spore Adherence, and Virulence in Metarhizium robertsii

“…This is in contrast to our observations for ⌬MBZ1, which suggests that, in addition to the functional divergence of paralogous bZIP-type TFs (15), the orthologous TFs could play divergent roles in different organisms. Deletion of the bZIP-type TF gene FGAP1 does not affect the pathogenicity of F. graminearum to wheat (11), but loss of the orthologous gene MOAP1 in M. oryzae completely abolishes its pathogenicity to rice (14). Likewise, other studies have found that the null mutants of MOATF1 of M. oryzae and FGATF1 of F. graminearum have reduced virulence, but the former are more sensitive to oxidative stress (12,13).…”

“…Different bZIP-type TFs have also been characterized in various filamentous fungal species, including Aspergillus nidulans (7,8), Neurospora crassa (9), and the plant pathogens Fusarium graminearum (10 -12) and Magnaporthe oryzae (13)(14)(15). Deletions and functional characterizations of these genes revealed that bZIP-type TFs are involved in mediating fungal development, sexuality, stress responses, secondary metabolisms, and especially the virulence of plant pathogens.…”

“…For example, the bZIP-type TF FGZIF1 was identified to be involved in the control of mycotoxin deoxynivalenol production, sexuality, and virulence in F. graminearum (11). MOAP1 of M. oryzae was functionally verified as a positive regulator of different target genes involved in growth, development, and pathogenicity (14). Genome analyses of insect fungal pathogens such as Metarhizium robertsii (16), Cordyceps militaris (17), and Beauveria bassiana (18) also identified an array of bZIP-type TFs present in their genomes.…”

N-Glycosylation of Effector Proteins by an α-1,3-Mannosyltransferase Is Required for the Rice Blast Fungus to Evade Host Innate Immunity

“…The impairment in the growth of invasive hyphae, therefore, can be attributed to ROS accumulation within plant cells due to the absence of Alg3. In addition to the Dslp1 and Dalg3 mutants, several other M. oryzae mutants have been reported to induce ROS accumulation in penetrated plant cells, including mutants disrupted in DES1 (Chi et al, 2009), ATF1 (Guo et al, 2010), AP1 (Guo et al, 2011), HYR1 (Huang et al, 2011), CHS6 , and CRC1 genes. DES1, AP1, ATF1, and HYR may be involved in ROS detoxification, because expression levels of ROS-detoxifying genes were significantly reduced in these mutants (Chi et al, 2009;Guo et al, 2010Guo et al, , 2011Huang et al, 2011;Adam et al, 2012).…”

Effect of addition amino acids on the mycelial growth and the contents of β-glucan and γ-aminobutyric acid (GABA) in Sparassis latifolia

“…Fungi의 GABA-shunt와 관련 한 기관과 생화학적 metabolism이 있다는 것이 밝혀지면 서 A. niger의 GABA-shunt에 대한 관심이 높아졌다 (Kumar and Punekar, 1997). 최근 Magnaporthe oryzae의 SSADH를 발현하는 gene (MoSSADH)이 규명되었고 mutants를 통해서 숙주식물체 표면에 뻗는 발아관 형성과 침투 생장, 일반적인 성장, 분생자 형성에 있어 가장 중요 한 유전자임이 밝혀졌다 (Guo et al, 2011). 앞서 확인한 아미노산의 균사 생장에 대한 긍정적인 영향은 GABA의 생성, 분해와 연관성이 있을 것이라 판단하였고, 균사체의 GABA 함량을 관찰하였다.…”