Functional Characterizaion Of The Gene Cptrp Associated With Growth In Cryphonectria Parasitica

Cryphonectria parasitica,the filamentous fungal pathogen of chestnut blight,shows less virulence after hypovirus infection.50HD09,derived from a T-DNA integrating in the genome of EP155,showed significant growth defect.The T-DNA was found inserting in the second exon of the cptrp,a gene encoded incomplete TRP domain.Functional complementation by introduction of an additional copy of cptrp restored normal phenotype as EP155,and confirmed that the disruption of cptrp was the sole cause of phenotypic changes of 50HD09.Real-time PCR analyses revealed that expression of cptrp was affected after the infection of hypovirus,and it was transcriptionally downregulated 2.2 times in EP155 with the presence of virus.Cptrp null mutants were constructed by homologous recombination.The phenotype of the null mutants was undistinguished with 50HD09.Compared with the wild-type strain EP155,cptrp null mutants displayed irregular colony edge,slow growth rate(9.04%and 6.18%of growth rate of EP155 for 5 and 10 days),increased conidiation(10 times of conidiation of EP155 for 14 days)and deep colony pigment.Deletion of cptrp never made influence of infection and accumulation of hypovirus CHV1-EP713.Compared to EP155,a reduction of 40%was observed in the canker area produced by the cptrp null mutant,and it was ascribed to defective growth rather than to impairments in virulence.These results suggested that cptrp gene is involved in growth and conidiation of C.parasitica,but not contributs directly to the fungal virulence.The function of this gene needs further investigation.