Analysis Of The Biological Functions Of The Blue Light Receptor Proteins WC-1 And WC-2 Of Beauveria Bassiana

Filamentous fungal insect pathogens,Beauveria bassiana have been widely applied for arthropod pest control.Light as an environmental signal are of special importance for fungal responses to the growth and development,in which blue light is considered one of the most important stressful signals.This study aims to provide the biological functions on the progresses of blue light receptor genes WC-1 and WC-2,and reveal how those genes conduct signal transduction and regulate the process of asexual development,which can understand the roles of WC-1 and WC-2 for pest control in B.bassiana.The blue-light photoreceptor WC-1 and WC-2 exist in B.bassiana that can response to light.In this study,we report that single deletions of the two white collar genes WC-1 and WC-2 resulted in different cell sensitivity to wall perturbation,oxidation or high osmolarity stressful signals.Western blot of the GFP-tagged WC-1 and WC-2 fusion proteins（WC-1::GFP or WC-2::GFP）were confirmed that WC-1::GFP is located in the cytoplasm under light/dark（L:D）cycles of 24:0 conditions,while the nucleus basically disappeared.With shortening daylight,the WC-1::GFP fusion protein gradually moved out of the cytoplasm and gathered in the nucleus in L:D 12:12,until it moved into the nucleus completely in L:D0:24 cycle.The WC-2::GFP has a significantly higher cytoplasmic intensity than the nucleus under L:D24:0.With shortening daylight,it gradually moved to nucleus.Until the full darkness,more aggregated in the nucleus than the cytoplasm.Conclusively,WC-1 and WC-2 sustain shuttle phenomenon in a daylight length-dependent manner and acts as light-dependent factors in B.bassiana.The study also found that deletion of any WC-1 or WC-2 caused significantly reduced conidiation capacity.After shortened the daylight in different light cycles,the single deletion mutant strain of（35）wc-1resulted in significant conidiation increases the sensitivity to cell wall perturbation（calcofluor white,CFW）and H₂O₂,while the（35）wc-2 increases the sensitivity to CFW and high osmolarity（Na CL）,respectively.Thus,they can at least response to two or more stressful signals in the Hog1 pathway.The virulence of either（35）wc-1 or（35）wc-2 against Galleria mellonella was drastically attenuated after entry into the insect haemocoel.The results showed that the LT₅₀ of WC-1 and WC-2 was delayed to 6.9±0.2 d and 8.4±0.3 d.Intriguingly,after injection the（35）wc-1 mutant strain,the insects almost alive for12 d,and the LT₅₀ could not be estimated by calculation,while the LT₅₀ of WC-2 strain was delayed to9.7±0.5 d.This results indicate the important roles of WC-1 and WC-2 in maintaining the virulence of fungus and the normal conidiation capacity in a daylight length-dependent manner.Our findings highlight diverse functions of WC-1 and WC-2 in B.bassiana.