Abstract:

NPR1 is one of important regulatory factors inducing expression of desease-resistant genes，and mainly acts in the up- or down-streams on salicylic acid signal transduction pathway. Full-length cDNAs of NPR1 homologous genes were screened from enriched full-length normalized cDNA library by pool-dilued PCR method in Nai’s leaves；young leaves in one-year grafted seedlings were sprayed with salicylic acid solutions of different concentrations，the differences in expression levels of the isolated NPR1 genes were detected by fluorescence quantitative PCR. The results showed that 4 full-length cDNAs of NPR1 homologous genes were obtained and named as PsNPR1，PsNPR3.1，PsNPR3.2 and PsNPR3.3 respectively；their responding full lengths were 2 442，1 827，2 244 and 2 615 bp；their reponding lengths of ORFs were 1 788，1 770，1 767 and 1 782 bp，encoding proteins containing 596，590，589 and 594 amino acids，respectively；the results of amino acid sequence alignment showed that coding regions of the 4 NPR1 homologous genes contained two conservative domains（BTB/POZ and ANK）and nuclear localization signal（NLS）；Nai’s PsNPR1 was clustered with Arabidopsis thaliana’s AtNPR1 and AtNPR2 forming a cluster，Nai’s PsNPR3.1，PsNPR3.2 and PsNPR3.3 were clustered with Arabidopsis thaliana’s AtNPR3 and AtNPR4 forming another cluster. The expression level of PsNPR1 was the highest in Nai’s young leaves sprayed with 1.0 mmol ? L-1 salicylic acid solutions；the expression levels of PsNPR1，PsNPR3.1 and PsNPR3.2 continuously increased in process of response to 1.0 mmol ? L-1 salicylic acid，and reached maximum at 30 hours after spraying，then tended to decrease，therefore，the optimal spraying concentration of salicylic acid was 1.0 mmol ? L-1，the optimal responsing time of 1.0 mmol ? L-1 salicylic acid was 30 hours.

Key words: Prunus salicina, salicylic acid, NPR1