RESUMEN
OBJECTIVE: By analyzing the function and mechanism of nitric oxide in initiating producing lignin peroxidases by phanerochaete chrysosporium, we studied the regulation mechanism triggering the secondary metabolism of white-rot fungi. METHODS: Mutant (pcR5305) and wild-type (pc530) strains of phanerochaete chrysosporium were respectively cultured under both the conditions of nitrogen limitation and nitrogen sufficiency. To compare their lignin peroxidases (LiP)-production and nitric oxide(NO)-production kinetics and their different influences on producing LiP after the NO donor Sodium Nitroprusside (SNP) and scavenger cPTIO were respectively added to the nitrogen limitation or sufficiency culture medium to show the function and mechanism of nitric oxide in initiating production of lignin peroxidases by white-rot fungi. RESULTS: Both strains produced nitric oxide (NO) under the two opposite nutritional conditions, but the levels of NO produced were related with the type of strain and the nutritional conditions. Strain pc530 produced NO requiring nutrition depletion and producing of NO was strongly delayed and reduced when it was cultured under nitrogen sufficiency condition. On the contrary, pcR5305 did not require nitrogen depletion to trigger and the levels of NO were higher than that of pc530. The results indicate that LiP content had positive correlation with NO value except the occurrence time of LiP peak value was later than that of NO. The ability of producing LiP was promoted after the NO donor SNP added, but SNP affected more on pc530 than pcR5305 in promoting producing LiP. 15mM cPTIO would greatly repress producing LiP, but could not completely restrain the synthesis of LiP for both strains. CONCLUSION: By producing NO, Phanerochaete chrysosporium triggers LiP synthesis. However, the evidences do not indicate that NO participates or effect directly in LiP synthesis. It is more likely that NO is reacting as an upstream signal molecule. Besides NO, there are other signal molecules that have a positive effect on NO levels also involving in the regulation producing LiP. The mechanism of the resistance to nutritional repression of pcR5305 in synthesizing lignin degrading peroxidases may be the answer to the different NO production mechanism of pcR5305 from pc530.