| Phytophthora species cause major disease problems worldwide on a wide range of crops.P.nicotianae causes tobacoo blask shank and disease on awide range of plant.Because of the great diversity in the genes Phytophthora,research on the pathogenic mechanism of P.nicotianae at molecular level be helpful to a full understanding of the biology of Phytophthora,which will be of criticed of importance for the development of the oretical proofs for disease control,and sustainabe crop prodection.We locus on avirulence genes Avr1b cloned from P.sojae and Avr3a cloned from P. infestans and the fact that the distritution oof genes on chromosomes show synthetic relationships among similar species,as revealed by comparative genomics,to constract physical maps spaming fo corresponding regions in the genome of P. nicotianae.We used conserved sequences surrounding Avr1b and Avr3a loci to screen a BAC library of P.nicotianae. Positive BACs were digested by restrict enzymes and gal seperated and analyzed.Finally,two P. nicotianae regions corresponding locus of Avrlb and Avr3a,both were about 160kb in range were constructed. Partial sequedcing of selected BAC clones showed that the constructed contigs showed synthetic relationships to the corresponding regions in P.sojae and P. infestans.This will facilitate a comparative genomics approach for the identifition of P. nicotianae.The constructed genomic regions more screened for transcribed sequences during pathogen infection using cDNA probes synthesis with total RNA isolated from do sensed plant tissues,got two 160kb long genome regions.Seneral positive fragments cloned and sequenced. Sequence blast indicated that most of the sequences matched with sequences of Hyaloperonospora parasitica,few matched with P.sojae and P. infestans. The function of protein an coded by these sequence was not clear. |
