AaCaM is required for infection structure differentiation and secondary metabolites in pear fungal pathogen Alternaria alternata

Abstract

Aims Calmodulin (CaM), acts as a kind of multifunctional Ca2+ sensing protein, which is ubiquitous in fungi, is highly conserved across eukaryotes and is involved in the regulation of a range of physiological processes, including morphogenesis, reproduction and secondary metabolites biosynthesis. Our aim was to understand the characteristics and functions of AaCaM in Alternaria alternata, the causal agent of pear black spot. Methods and results A 450 bp cDNA sequence of AaCaM gene of A. alternata was cloned by the PCR homology method. Sequence analysis showed that this protein encoded by AaCaM was a stable hydrophilic protein and had a high similarity to Neurospora crassa (CAA50271.1) and other fungi. RT‐qPCR analysis determined that AaCaM was differentially upregulated during infection structural differentiation of A. alternata both on hydrophobic and pear wax extract‐coated surface, with a 3.37‐fold upregulation during the hydrophobic induced appressorium formation period (6 h) and a 1.46‐fold upregulation during the infection hyphae formation period (8 h) following pear wax induction. Pharmaceutical analysis showed that the CaM‐specific inhibitor, trifluoperazine (TFP), inhibited spore germination and appressorium formation, and affected toxins and melanin biosynthesis in A. alternata. Conclusions AaCaM plays an important role in regulating infection structure differentiation and secondary metabolism of A. alternata. Significance and impact of study Our study provides a theoretical basis for further in‐depth investigation of the specific role of AaCaM in the calcium signalling pathway underlying hydrophobic and pear wax‐induced infection structure differentiation and pathogenicity of A. alternata.

Protein Kinase C Is Involved in Vegetative Development, Stress Response and Pathogenicity in Verticillium dahliae

“…PKCs are involved in the Ca 2+ signaling pathway and play important roles in fungal growth, development, and pathogenicity, and are potential targets of antifungal drugs [ 11 , 12 , 14 , 43 ]. PKCs comprise an important class of pathogenic factors, and studies have confirmed that they are involved in the pathogenesis of a variety of phytopathogenic fungi [ 16 , 20 ].…”

“…Notably, previous studies have demonstrated that V. dahliae primarily thrives as stress-resistant microsclerotia in adverse environments. The formation of microsclerotia is accompanied by the accumulation of melanin, which finally transforms into mature black microsclerotia with strong stress resistance [ 30 , 33 , 43 , 61 ]. The present study revealed that VdPKC regulates the transcription of melanin and sclerotia-related genes ( Figure 5 D), thereby affecting the formation of microsclerotia and melanin.…”

Updating Insights into the Regulatory Mechanisms of Calcineurin-Activated Transcription Factor Crz1 in Pathogenic Fungi

“…Upon Ca 2+ presence, the activated CaM binds to the CNA and CNB complexes to form a fully activated trimer [ 81 ], and then activated CaN dephosphorylates Crz1 and transfers it to the nucleus to regulate the expression of Crz1-dependent genes [ 11 , 82 ]. In fungi, the CaN-Crz1 signaling pathway is also conserved and involved in many biological processes, such as cell growth, infection structure differentiation, cell wall integrity, pathogenicity and stress response [ 83 , 84 , 85 , 86 , 87 ] ( Figure 1 ). The Figure 1 only depicts genes in the calcium signaling pathway that are closely linked to Crz1 or directly regulated by Crz1.…”