THE DIFFERENTIAL EXPRESSION OF RESISTANT GENES RELATED TO CUCUMBER SCAB DISPLAYED BY CDNA-AFLP

Abstract

In order to understand the molecular basis of the inheritance of scab-resistance and provide basic information for disease-resistant breeding in cucumber. The seedlings of resistant inbred line 'HX613' and susceptible inbred line 'HX36' were inoculated by spraying the pathogenic suspension of Cladosporium cucumerium with sterilized water as control. After 6, 12, 24, 48, 72, 96, and 146 h of inoculation, the covered tender leaves from the plants of different treatments were sampled. RNA was extracted from the leaves and reverse-transcribed to cDNA. The differential expression of genes resistant-related to scab was analyzed by cDNA-AFLP. Two hundred sixteen TDFs (Transcriptic derived fragment) were screened out. Among them, 27 TDFs was enhanced expression, and the expression of 12 TDFs was weakened, 154 TDFs was transient expression and 23 TDFs was a constitutive expression, accounting for 12.5, 5.6, 71.3 and 10.6% respectively. We cloned and sequenced 8 TDFs which expressed strongly and repeatedly by same primers. Homology analysis indicated that TDF 'E 11 M 59 104' was related to the gene participating in defense reaction and substance decomposition in cell; TDF 'E 11 M 59 489' was homologous to pathogenesis-related proteins; E 25 M 63 203 is 96% homologous with resistant protein. Other 5 TDFs were involved in cell-cycle regulation, transmembrane movements and metabolism etc. The above results showed that the resistant reaction of cucumber to scab dealt with multiple aspects of pathology, physiology, biochemistry and molecular biology in the interaction of the plant and pathogen.