Abstract: In order to reveal the biological function of abscisic acid(ABA) receptor genes,NtPYR1 and NtPYL9,in Nicotiana tabacum L.(N.tabacum),the encoding sequences of PYR1 and PYL9 in Arabidopsis thialianawere used as probes to find out homologous expressed sequence tags(ESTs) from N.tabacum genome in NCBI.Specific primers were designed following EST stitching,and NtPYR1 and NtPYL9 genes were cloned from cDNA library of cv.Honghuadajinyuan(N.tabacum).The open reading frames(ORFs) of NtPYR1 and NtPYL9 were 678 bp and 564 bp in length and encoded proteins of 225 and 187 amino acids,respectively.Both NtPYR1 and NtPYL9 contained a conserved hydrophobic domain and belonged to PYR/PYL/RCAR ABA receptor gene family.The similarity between NtPYR1/NtPYL9 and their homologous proteins in Solanum lycopersicum reached 79.10% and 95.24%,respectively.The results of phylogenetic analysis showed that the genetic distances between NtPYR1/NtPYL9 and their homologous genes in tomato and potato were the nearest,which indicated that PYR1 and PYL9 genes were relatively conserved in Solanaceae family.The quantitative PCR analysis of the expression patterns of NtPYR1 and NtPYL9 showed that the two could be expressed in various tissues,particularly in cotyledons and fibrous roots.The expression of NtPYR1 and NtPYL9 could be inhibited by ABA,while induced by H₂O₂,it implied that they might take part in the stress response process in tobacco plants.