中文摘要：

细胞色素P450在各种内源和外源物质代谢中起着非常重要的作用。利用豌豆蚜Acyrthosiphon pisum基因组mRNA和氨基酸数据库研究P450基因功能的进化规律。通过生物信息学方法对豌豆蚜全基因组P450进行分析,结果显示：在豌豆蚜基因组中发现69个P450基因,它们分别属于13个P450家族和18个亚家族,是一个典型的多基因家族。进一步将这些基因与豌豆蚜ESTs数据库进行了比对分析,其中39个候选基因有EST证据,证明了这些P450基因在转录水平的真实性。以氨基酸相似度大于60%为标准对豌豆蚜基因组中P450基因进行分组,69个P450基因中,除18个基因序列因差异太大,不能被归入任何一组,其余51个可归入10个组,其中8个组（包含47条序列）适合于正选择和基因转换分析。正选择和基因转换分析结果表明：仅有1个组（含9个基因）显著受到正选择压力作用,正选择概率大于95%的氨基酸位点分别是20T和27N,20T位于底物识别位点SRS1,27N位于D-helix;有3个组（包含8个基因）显示显著的基因转换事件。参与基因转换的基因均为CYP4家族成员,分别是CYP4C,CYP4G和CYP4V亚家族。参与基因转换的成员之间的蛋白相似度较高（70%～95%）,且XM_001944991与XM_001951794同存在于SCAFFOLD12542上,XM_001945510与XM_001944057同存在于SCAFFOLD7010上。这可能暗示豌豆蚜P450基因通过基因复制,然后通过基因转换使P450获得新的功能,以适应多变的生存环境。此外,鉴定出20个不同的基序,其中有5条基序在90%以上的基因中出现。

英文摘要：

Cytochrome P450 plays a dominant role in the metabolism of a wide variety of both endogenous and xenobiotic substances. The evolution of P450 gene function was analyzed in the genome of the pea aphid,Acyrthosiphon pisum,using the mRNA and amino acid data. A genome-wide analysis of P450 genes was performed in pea aphid genome by bioinformatical methods. The results showed that sixty-nine P450 genes were discovered in pea aphid genome,which are of a typical superfamily and belong to 13 families and 18 subfamilies. We collected expression sequence tag （EST） evidence for 39 putative P450s genes,which are expressed at the transcriptional level and more likely to be true P450s. Because of significant differences in gene sequences,among 69 P450 genes 18 genes could not partitioned into any group,while the rest 51 P450 genes were partitioned into 10 groups by a criterion that the genes belong to a group when their amino acid identity is more than 60%. Positive selection and gene conversion were analyzed in 8 groups （including 47 genes）. Positive selection was detected in only one group （including 9 genes）. The positively selected sites with a more than 95% probability were 20T and 27N,located in substrate recognition site （SRS1） and D-helix,respectively. The significant gene conversion events were detected in 3 groups （8 sequences）. P450 genes that identified gene conversion events were members of CYP4 family,which were CYP4C,CYP4G and CYP4V subfamily,respectively. Protein similarity between P450 genes with gene conversion was 70%-95%. P450 genes with gene conversion lay in the same scaffold,e.g.,M_001944991 and XM_001951794 lay in SCAFFOLD12542,while XM_001945510 and XM_001944057 lay in SCAFFOLD7010. The results suggest that P450 genes may gain new function through gene duplication and gene conversion. Moreover,twenty motifs were identified,of which 5 motifs existed in over 90% of P450 genes.