Daylight length‐dependent translocation of VIVID photoreceptor in cells and its essential role in conidiation and virulence of Beauveria bassiana

• Published in: Environmental microbiology 2018-01, Vol.20 (1), p.169-185
• Main Authors: Tong, Sen‐Miao, Zhang, An‐Xue, Guo, Chong‐Tao, Ying, Sheng‐Hua, Feng, Ming‐Guang
• Format: Article
• Language: English
• Subjects: Animals; Beauveria - pathogenicity; Beauveria bassiana; Capacity; Cells; Clonal deletion; Cuticles; Cycles; Cytoplasm; Darkness; Daylight; Deletion mutant; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungi; Fusion protein; Gene silencing; Genes; Hyphae - growth & development; Insects; Length; Light; Moths - microbiology; Nuclei; Nucleus; Photoreceptors; Photoreceptors, Microbial - genetics; Photoreceptors, Microbial - metabolism; Pigmentation; Proteins; Secretion; Spores, Fungal - growth & development; Transcription; Translocation; Vacuoles; Virulence; Virulence Factors; White light
• ISSN: 1462-2912; 1462-2920
• DOI: 10.1111/1462-2920.13951

Summary The fungal insect pathogen Beauveria bassiana has the blue‐light photoreceptor VIVID (VVD) but lacks a pigmentation pattern to trace its light responses. Here, we show that the fungal vvd is transcriptionally expressed, and linked to other blue/red photoreceptor genes, in a daylight length‐dependent manner. GFP‐tagged VVD fusion protein was localized to periphery, cytoplasm and vacuoles of hyphal cells in light/dark (L:D) cycles of 24:0 and 16:8 and aggregated in cytoplasm with shortening daylight until transfer into nuclei in full darkness. Deletion of vvd caused more reduced (91%) conidiation capacity in L:D 12:12 cycle of blue light (450/480 nm) than of yellow‐to‐red (540–760 nm) and white lights (∼70%). The conidiation defect worsened with shortened daylight in different L:D cycles of white light, coinciding well with drastic repression of key activator genes in central development pathway. Intriguingly, the deletion mutant displayed blocked secretion of cuticle‐degrading Pr1 proteases, retarded dimorphic transition in insect haemocoel, and hence a lethal action twice longer than those for control strains against Galleria mellonella regardless of the infection passing or bypassing insect cuticle. Conclusively, VVD sustains normal conidiation in a daylight length‐dependent manner and acts as a vital virulence factor in B. bassiana.