胁迫条件下山新杨 PdPapMYC2 基因的组织表达模式

Tissue-specific expression profiles of PdPapMYC2 in Shanxin poplar under various stresses

【目的】解明山新杨PdPapMYC2基因在生物胁迫、非生物胁迫及激素诱导下的组织表达模式。【方法】克隆山新杨PdPapMYC2基因,采用生物信息学技术分析其编码蛋白特性。采用qRT-PCR技术分析PdPapMYC2在山新杨顶尖、茎、叶和根等组织中的表达量,以及其在盐(NaCl)、碱(Na 2CO 3)和高渗透压(PEG6000)3种非生物胁迫处理,核盘菌(Sclerotinia sclerotiorum)、立枯丝核菌(Rhizoctonia solani)、尖孢镰刀菌(Fusarium oxysporum)、链格孢菌(Alternaria alternata)和金黄壳囊孢菌(Cytospora chrysosperma)5种生物胁迫处理及脱落酸(ABA)、茉莉酸(JA)和水杨酸(SA)3种激素诱导下的组织表达量变化。【结果】PdPapMYC2基因长1944 bp,编码647个氨基酸,存在bHLH-MYC_N superfamily和bHLH_SF superfamily保守结构域。预测PdPapMYC2蛋白定位在细胞核;二级结构主要由α-螺旋和无规则卷曲构成,三级结构与拟南芥4rru.1.A模型的一致性最高。系统进化结果显示,PdPapMYC2与毛白杨PtMYC2的亲缘关系最近。qRT-PCR分析结果显示,PdPapMYC2基因在山新杨顶尖、叶、茎和根中均有表达;与对照(CK)处理相比,在NaCl、Na 2CO 3和PEG6000胁迫处理下,顶尖部位PdPapMYC2的表达量均显著下调(P<0.05);成熟叶中PdPapMYC2的表达量在NaCl胁迫时显著上调(P<0.05),在碱和高渗透压胁迫处理中下调;3种胁迫处理下其在根中的表达量均下调,但均未达显著水平。与对照(CK)处理相比,5种土传致病真菌胁迫48 h后,顶尖中PdPapMYC2表达量均下调,成熟叶中表达量仅在链格孢菌诱导下略上调,根部表达量在尖孢镰刀菌、金黄壳囊孢菌、链格孢菌和核盘菌作用下上调。JA诱导下PdPapMYC2在各组织中的表达量均显著上调(P<0.05),ABA和SA诱导下其在各组织中的表达量均下调。【结论】PdPapMYC2基因在山新杨多组织中表达,参与植物抵御逆境胁迫,并响应相关激素诱导。

【Objective】This study aimed to elucidate the tissue-specific expression profiles of the PdPapMYC2 gene in the‘Shanxin’hybrid poplar(Populus davidiana×P.alba var.pyramidlis,cv‘Shan-xin’)under biotic stress,abiotic stress and hormone induction.【Method】The PdPapMYC2 gene was cloned and its coded protein was analyzed by bioinformatic tools.Quantitative reverse transcription polymerase chain reaction(qRT-PCR)assays were performed to analyze the expression profiles of PdPapMYC2 in different compartments(referred to as tissues hereafter)of poplar including shoot tip,different compartments of stem,leaves and roots.The changes of the tissue-specific expression levels of PdPapMYC2 were also studied under three abiotic treatments of salt stress(NaCl),alkali stress(Na 2CO 3)and high osmotic stress(PEG6000),five biotic stress treatments of Sclerotinia sclerotiorum,Rhizoctonia solani,Fusarium oxysporum,Alternaria alternata and Cytospora chrysosperma infection,and induction of three phytohormones including abscisic acid(ABA),jasmonic acid(JA)and salicylic acid(SA).【Result】The PdPapMYC2 gene was 1944 bp in length and encoded a 647-amino-acid protein containing a conserved bHLH-MYC_N superfamily domain and a conserved bHLH_SF superfamily domain.The subcellular localization of the PdPapMYC2 protein was predicted to be in the nucleus.The secondary structures mainly consisted ofα-helices and random coils.Tertiary structure analysis suggested the highest structural consistency between PdPapMYC2 and 4rru.1 of Arabidopsis.Phylogenetic analysis showed that PtMYC2 in P.tomentosa was the most closely related to PdPapMYC2.The qRT-PCR assays showed that PdPapMYC2 was constitutively expressed in shoot tips,stems,leaves and roots.Under NaCl,Na 2CO 3 and PEG6000 stress,the relative expression of PdPapMYC2 in shoot tip was significantly down-regulated(P<0.05).In mature leaves,PdPapMYC2 expression was significantly up-regulated under NaCl stress(P<0.05)and down-regulated under alkali and high osmotic stresses.In roots,PdPapMYC2 expression was down-regulated under all three abiotic treatments without significant differences.After 48 hours of infection by five soil-borne pathogenic fungi,PdPapMYC2 expression was down-regulated in shoot tips and it was slightly up-regulated when induced by Alternaria alternata.In roots,PdPapMYC2 expression was up-regulated under the induction of Fusarium oxysporum,Cytospora chrysosperma,Alternaria alternata and Sclerotinia sclerotiorum.PdPapMYC2 expression was significantly up-regulated under JA induction(P<0.05)and down-regulated under ABA or SA induction in all tissues.【Conclusion】PdPapMYC2 gene expressed in multiple tissues and involved in regulating resistance of plants to various stresses and responding to stress-related hormones.