Characterization and Functional Analysis of a New Calcium/Calmodulin-Dependent Protein Kinase (CaMK1) in the Citrus Pathogenic Fungus Penicillium italicum

Abstract

Calcium (Ca2+)/calmodulin-dependent protein kinases (CaMKs) act as a class of crucial elements in Ca2+-signal transduction pathways that regulate fungal growth, sporulation, virulence, and environmental stress tolerance. However, little is known about the function of such protein kinase in phytopathogenic Penicillium species. In the present study, a new CaMK gene from the citrus pathogenic fungus P. italicum, designated PiCaMK1, was cloned and functionally characterized by gene knockout and transcriptome analysis. The open reading frame of PiCaMK1 is 1209 bp in full length, which encodes 402 amino acid residues (putative molecular weight ~45.2 KD) with the highest homologous (~96.3%) to the P. expansum CaMK. The knockout mutant ΔPiCaMK1 showed a significant reduction in vegetative growth, conidiation, and virulence (i.e., to induce blue mold decay on citrus fruit). ΔPiCaMK1 was less sensitive to NaCl- or KCl-induced salinity stress and less resistant to mannitol-induced osmotic stress, indicating the functional involvement of PiCaMK1 in such environmental stress tolerance. In contrast, the PiCaMK1-complemented strain ΔPiCaMK1COM can restore all the defective phenotypes. Transcriptome analysis revealed that knockout of PiCaMK1 down-regulated expression of the genes involved in DNA replication and repair, cell cycle, meiosis, pyrimidine and purine metabolisms, and MAPK signaling pathway. Our results suggested the critical role of PiCaMK1 in regulating multiple physical and cellular processes of citrus postharvest pathogen P. italicum, including growth, conidiation, virulence, and environmental stress tolerance.

CryptoCEN: A Co-Expression Network for Cryptococcus neoformans reveals novel proteins involved in DNA damage repair

“…Previous studies have shown that this pathway can play a role in cell cycle control in S . cerevisiae and other organisms [ 89 ], with a function at the G 2 /M checkpoint [ 90 – 92 ]. In C .…”

“…This gene encodes a calmodulin-dependent kinase (CaMK) and serves as an effector of the calcium-calcineurin signaling pathway, an important component of fungal stress responses [86][87][88]. Previous studies have shown that this pathway can play a role in cell cycle control in S. cerevisiae and other organisms [89], with a function at the G 2 /M checkpoint [90][91][92]. In C. neoformans, loss of CMK1 may inhibit the mutant from the appropriate stress-induced cell cycle arrest, leading to increased growth in the presence of the cellular stress.…”

Discovery and Transcriptional Profiling of Penicillium digitatum Genes That Could Promote Fungal Virulence during Citrus Fruit Infection

“…Fungal growth, sporulation, virulence, and stress tolerance are regulated through Ca 2+ -involved cross-linking mechanisms, including DNA replication and damage repair, cell cycle and nuclear division, and MAPK signaling. In Penicillium italicum, gene knockout and complementation analysis indicated the requirement of the PiCaMK1 in the fungal vegetative growth, sporulation, full virulence, and responses to salt (salinity) and mannitol (osmotic) stresses [50]. Additionally, in this group, although less represented, is argininosuccinate lyase (PDIP_06990).…”

Special Issue “Control of Postharvest Pathogenic Penicillium”

“…Finally, Li and co-workers [4] analyzed Calcium (Ca2+)/calmodulin-dependent protein kinases (CaMKs), identifying a new gene in P. italicum (PiCaMK1). Results obtained in this work suggest that PiCaMK1 function involves the regulation of multiple physical and cellular processes of this pathogen, including growth, conidiation, virulence, and environmental stress tolerance.…”