[Objective]This study aimed to clone a full length cDNA ofPbChiIV fromPyrus bretschneideri‘Yali’ and detect the expression characteristics ofPbChiIV in root, stem, leaf,fruit and the expression after treatment with the salicylic acid(SA) and Botryosphaeria berengeriana de. Not. f. sp.piricola(Nose) Koganecawa et. Sokwwa.[Method]The full lengthof PbChiIV was obtained fromPyrus bretschneideri‘Yali’ using specific primers. The similarity of the nucleotide sequence and deduced amino acid sequence was analyzed by using BLAST on NCBI. BiotEdit software was used to compare the amino acid sequence. Phylogenetic tree was constructed by using MEGA6.0. Quantitative real-time PCR (qRT-PCR) was performed to determine the expression pattern ofPbChiIV in different tissues and the expression of this gene after treatment with SA andB.berengeriana. f. sp.piricola.[Result]The cDNA lengths ofPbChiIVgenes was 819 bp (GenBank accession number: KJ872676), encoding 272 amino acids. The deduced amino acid sequence shares 100%, 79%, 73%, 73%, 72%, 72%, 72%, 69%, 68%, 67%, 67%, 65%, 67% and 62% identity with P. pyrifoliaACM45716.1,Populus trichocarpa XP_006376418.1,Vitis vinifera NP_001268173.1,Arabidopsis thaliana CAA74930.1, Medicago sativa ACL36992.1,Medicago truncatulaAAR87869.1,Vigna unguiculata CAA61281.1,Corylus heterophylla AEM97876.1,Galega orientalis AAP03085.1,Vitis vinifera NP_001268075.1,Vitis pseudoreticulata ABY66958.1,Vitis vinifera AAB65777.1,Nicotiana tabacum BAF44533.1 andGossypium barbadense AER29902.1. This gene belongs toIVchitinase gene. Expression analysis showed that the expression ofPbChiIV in root was the highest, which was 4.32 and 2.96 times compared with stem and leaf, respectively. Followed by the expression in fruit, which was 2.48 and 1.70 times compared to that of stem and leaf, respectively. In the young fruit and mature fruit, the expression of the gene could be induced by SA andB.berengeriana. f. sp. piricola. The highest expression of the gene was 2.83 and 3.80 times compared with controls after treatment with SA, respectively. The highest expression of the gene was 1.82 and 1.66 times as compared with controls after treatment with pathogen, respectively. The highest expression of the gene was 2.49 and 3.43 times as compared with controls after treatment with SA and pathogen. In addition, the expression was up to the peak at 72, 24 and 72 h after treatment with SA and pathogen, respectively.[Conclusion]PbChiIVmay be involved in SA-mediated basic signaling pathway of plant defense responses and disease resistance signal transduction network. It is speculated thatPbChiIV is involved in defense responses mediated byB.berengeriana. f. sp.piricola. It might play an important role in disease resistance.%【目的】从鸭梨果实中克隆PbChiIV的全长cDNA序列，检测PbChiIV在根、茎、叶、果实以及在水杨酸（SA）和梨轮纹病菌诱导下的表达特性，以探讨该基因与SA信号转导及抗梨轮纹病菌的相关性。【方法】设计特异引物，克隆PbChiIV的全长序列，将测序得到的核苷酸序列和推导的氨基酸序列在NCBI上用BLAST进行序列相似性分析，利用 BiotEdit 软件对氨基酸序列进行比对，利用 MEGA6.0构建系统发育树，利用实时荧光定量PCR技术分析该基因在梨不同组织以及在SA和梨轮纹病菌诱导下的表达。【结果】克隆了PbChiIV的cDNA序列为819 bp，GenBank数据库登录号为KJ872676。生物信息学分析表明，PbChiIV编码272个氨基酸，与沙梨的同源性达100%，与毛果杨（XP_006376418.1）、葡萄（NP001268173.1）、拟南芥（CAA74930.1）、紫花苜蓿（ACL36992.1）、蒺藜苜蓿（ AAR87869.1）、豇豆（ CAA61281.1）、榛子（ AEM97876.1）、东方山羊豆（ AAP03085.1）、葡萄（NP_001268075.1）、华东葡萄（ABY66958.1）、葡萄（AAB65777.1）、烟草（BAF44533.1）和海岛棉（AER29902.1）的同源性分别为79%、73%、73%、72%、72%、72%、69%、68%、67%、67%、65%、67%和62%，属于第IV类几丁质酶基因。表达分析表明，PbChiIV在根中的表达量最大，分别是茎和叶的4.32和2.96倍，其次是在果实中的表达量，分别是茎和叶的2.48和1.70倍，在叶片和茎中的表达相对较低。在鸭梨幼果和成熟期果实中，SA和梨轮纹病菌均可诱导该基因表达。SA处理后基因的最大表达量是对照的2.83和3.8倍，病原菌处理后基因的最大表达量是对照的1.82和1.66倍，SA、病原菌处理后基因的最大表达量是对照的2.49和3.43倍，表达量分别在72、24和72 h达到最大值。【结论】PbChiIV可能参与SA介导的植物抗病防卫反应的信号通路，推测其参与梨轮纹病菌引起的防卫反应，在鸭梨抗病过程中起作用。
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