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核桃Julgans regia是胡桃科Juglandaceae核桃属Juglans核桃组植物[1]。中国种植核桃的历史可追溯到3 000 a前,且核桃分布广泛[2],品种繁多,产量高。中国为核桃六大主产国之一[3]。有关研究显示,在城区内大面积种植核桃,并搭配其他园林植物,可有效减轻颗粒物污染浓度。核桃具有极高的生态价值[4]。核桃木材外观优美、质地坚硬、材性优良,可做家具、木地板等;核桃青皮中的萘醌类物质可作染料,黄酮类物质可作抗氧化药品[5]。核桃果实富含蛋白质、磷脂以及维生素B1等能增强细胞活力、提高脑神经功能的物质,具有极高的药用价值,被称为“21世纪的超级食品”[6−7]。
恶劣的生长环境会导致核桃停止发育甚至死亡,如重度干旱环境等[8]。中国干旱、半干旱区面积约占国土面积的1/3以上,干旱地区降水稀少,水资源匮乏,无法满足核桃生长需求[9−10]。目前研究发现,抗旱关键酶基因包括α糖类、脯氨酸合成酶、甜菜碱,抗旱相关联蛋白包括LEA (late embryogenesis abundant)家族蛋白、蛋白激酶SnRK2等,其中LEA 第二家族成员脱水素蛋白(dehydrin, DHN)最早于受水分胁迫的水稻Oryza sativa中被发现,后来被证实广泛存在于植物细胞中[11]。许多研究都表明:非生物逆境胁迫下,植物中DHN基因的表达和积累与植物适应逆境的能力相关。如刘慧春等[12]将牡丹Paeonia suffruticosa PsDHN1基因转入拟南芥Arabidopsis thaliana中,发现转基因拟南芥耐涝抗旱水平明显优于野生型。史学英等[13]将从小麦Triticum aestivum中获得的DHN14基因转入大肠埃希菌Escherichia coli,发现可以提高在低温、干旱、金属离子等非生物胁迫下大肠埃希菌的存活率。LIU等[14]将玉米Zea mays中提取的ZmDHN13转入烟草Nicotiana tabacum,发现可显著提升转基因烟草对氧化损伤的耐受性。DHN可以结合金属离子,从根本上减少活性氧(ROS)的产生;DHN还可以结合DNA,保护其不受外界环境压力带来的损害;DHN非特异性地与生物膜结合,从而维持生物膜结构的稳定性等[15]。
在全球干旱的大背景下,水资源短缺仍会是未来中国甚至全球面临的主要问题,因此,研究植物的抗旱机制及挖掘抗旱基因都具有重要意义[16]。本研究分析了核桃脱水素JrDHN基因对干旱逆境胁迫的响应机制,为该基因进一步应用于核桃抗旱分子标记辅助育种提供参考依据,为利用基因工程手段培育抗旱核桃新品种提供理论依据。
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野生型核桃(WT)来自浙江农业大学省部共建亚热带森林培育国家重点实验室的奇异核桃J. hindsii×J. regia苗。前期已获得奇异核桃JrDHN过表达体胚,并萌发获得JrDHN过表达株系幼苗,后经扩繁并分为JrDHN1、JrDHN2、JrDHN3等3个株系,获得每株系50株生长健壮,长势一致的组培苗后,进行后续阳性鉴定及干旱胁迫试验(图1)。核桃苗于培养室中培养,培养室温度为(25±2) ℃,湿度为80%~85%,光照强度为15 000~20 001 lx,光照周期黑暗8 h/光照16 h。
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选用北京天根生化科技有限公司的多糖多酚植物总 RNA 提取试剂盒提取核桃体胚的 RNA,基因克隆及后续的验证过程采用 TaKaRa 公司的 cDNA 反转录试剂盒。以反转录cDNA为模板进行荧光定量PCR (qPCR)表达分析,采用NCBI网站在线设计引物,引物见表1。qPCR反应体系为:TB Green 0.5 μL,F/R primer 0.2 μL,cDNA 0.4 μL,ddH2O 4.2 μL。反应程序为:95 ℃ 10 min,95 ℃ 10 s,60 ℃ 31 s,40个循环;95 ℃ 15 s,60 ℃ 1 min,95 ℃ 30 s,60 ℃ 15 s。
表 1 qPCR引物
Table 1. qPCR primers
引物 序列(5′→3′) Actin-F ATGATGTCAAGGTTAAGGACTC Actin-R CACAATGATCTCAGCTCCG QJrDHN-F ATTCAGCTCACCGACGAACA QJrDHN-R CTCCTCATGCTGCTGCTTCT -
在体式荧光显微镜下观察再生JrDHN过表达植株茎和茎横切中绿色荧光标记蛋白(GFP)荧光激发情况,散发绿色荧光的植株为阳性植株。
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配置质量分数为5%PEG
8000 的DKW固体培养基,模拟干旱胁迫处理,分别设置模拟干旱胁迫时间分别为7、14、21、28 d的处理组,以培养于DKW正常培养基(001)中的核桃体苗为对照组,每组设置3个生物学重复。 -
在模拟干旱环境中处理0和14 d后,分别剪取同一部位WT和JrDHN过表达植株的叶片,在叶片下表面涂抹1层指甲油,风干后撕下盖上盖玻片在生物显微镜下观察并拍照。取0 d叶片加石英砂研磨,在显微镜下观察并记录叶绿体形态。
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分别剪取干旱胁迫处理7、14、21、28 d的JrDHN过表达株系和WT叶片,于大试管中加入20 mL配置好的DAB (1.0 g·L−1)、NBT (0.5 g·L−1)染液。室温下避光染色1~3 h,加入30 mL 体积分数为95%的乙醇,将大试管置于100 ℃沸水中水浴加热15 min,将叶绿素完全洗脱干净,之后固定拍照。
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分别取WT及JrDHN1干旱胁迫7、14、21、28 d的叶片0.1 g,加入10 mL 体积分数为 95%的乙醇溶液。黑暗条件下浸提48 h。以体积分数为95%乙醇为空白对照,测定波长663和646 nm处的吸光度,按叶绿素总质量分数=[20.2D(645)+8.2D(663)]×[V/(1 000W)]公式计算,其中V表示叶绿素提取液总体积,W表示所用叶片鲜质量。超氧化物歧化酶(SOD)、过氧化酶(POD)、过氧化氢酶(CAT)活性及超氧阴离子自由基(O2·−)、过氧化氢(H2O2)、丙二醛(MDA)均使用苏州科铭生物技术有限公司试剂盒进行测定。具体方法见使用说明书。
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Ca2+与 CaM形成的复合物可以与线粒体膜上的 NADKc结合,驱动RBOH蛋白产生细胞外ROS[17],从而促进胞外ROS向胞内转移[18]。通过这种方式,可以改变细胞质中信号成分的氧化还原状态,从而调节多种蛋白质和转录因子[19],后续可以调节一系列抗旱相关基因的表达,如ADH、SOD、POD基因等[20]。因此,对WT及JrDHN1在干旱胁迫28 d下核桃基因组中的ABA信号转导通路途径中的关键节点基因MYB、ADH、CAM表达量进行qPCR检测。测定方法同上。
Response of dehydrin JrDHN gene in walnut to drought stress
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摘要:
目的 探究奇异核桃Juglans hindsii × J. regia JrDHN过表达株系在干旱过程中体内的生理与分子响应及其分子机制,为培育核桃J. regia抗旱品种提供理论依据。 方法 对生长健壮的过表达JrDHN核桃苗(JrDHN1、2、3)进行不同时间的聚乙二醇(PEG)模拟干旱胁迫处理,野生型奇异核桃苗(WT)为对照。从核桃苗的表型、抗氧化酶活性、活性氧含量等多方面观察过表达JrDHN株系对干旱胁迫的响应。通过荧光定量PCR (qPCR)对体内的抗旱相关基因MYB、ADH、CAM做了表达量分析。 结果 阳性植株经qPCR验证,证实JrDHN基因在核桃苗中过表达,在JrDHN1、2、3中的表达量分别为WT的2.55、1.72、1.49倍;干旱处理0~28 d下过表达株系的表型均优于WT,干旱处理14 d时,JrDHN过表达株系的气孔开度比均显著低于WT;抗氧化酶(SOD、POD、CAT)活性均呈先升高后降低的趋势,且在14 d时达到最大值,其中JrDHN1的过氧化酶活性均高于WT,SOD及POD差异极显著(P<0.01),CAT活性差异显著(P<0.05);干旱处理28 d时叶绿素质量分数达到最小值,此时JrDHN过表达株系叶绿素极显著高于WT (P<0.01);丙二醛(MDA)、过氧化氢(H2O2)和超氧阴离子自由基(O2·−)含量随着干旱时间的延长呈逐渐上升趋势,在28 d时达到最大值,JrDHN1 的MDA、H2O2和O2·−含量均极显著低于WT;抗旱相关基因MYB、ADH、CAM的表达量均呈先上升后下降的趋势,14 d时,MYB、ADH、CA基因表达量均显著高于WT (P<0.05)。 结论 JrDHN过表达转基因核桃苗在PEG模拟干旱胁迫下的表型、光合能力和抗氧化能力均强于WT,JrDHN在模拟干旱胁迫下可以有效提升抗氧化酶系统活力,清除活性氧,减少细胞受到的损伤,从而提高植株的抗旱性。图8表1参34 Abstract:Objective This purpose was to investigate the physiological and molecular responses, as well as the molecular mechanisms, of Juglans hindsii×J. regia overexpressing line JrDHN during drought stress, to provide theoretical basis for breeding drought-resistant J. regia (walnut) cultivars. Method Healthy overexpressing walnut JrDHN were subjected to drought stress at different time points. The response of the overexpressing JrDHN line to drought stress was observed from various aspects including phenotype, antioxidant enzyme activity, and reactive oxygen species content. Quantitative PCR was conducted to analyze the expression levels of drought-related genes MYB, ADH, and CAM in plant tissues, exploring the molecular mechanism by which overexpression of JrDHN gene affects plant drought resistance. Result The results confirmed the overexpression of JrDHN gene in walnut seedlings, with expression levels in JrDHN1, 2, 3 being 2.55, 1.72, and 1.49 times higher than the WT respectively. Phenotypic traits of the overexpressing JrDHN line were superior to WT after 1−4 weeks of drought treatment, with significantly lower stomatal aperture in the overexpressing JrDHN line compared to WT after 2 weeks of drought treatment. The activities of antioxidant enzymes (SOD, POD, CAT) showed an initial increase followed by a decrease trend, reaching maximum values at 2 weeks, with SOD and POD activities in JrDHN1 significantly higher than WT (P<0.01), and CAT activity showing significant difference (P<0.05). Chlorophyll content reached its minimum after 4 weeks of drought treatment, with significantly higher levels in the overexpressing JrDHN line compared to WT. Levels of MDA, H2O2, and O2·− increased gradually with prolonged drought stress, reaching maximum values at 4 weeks, with significantly lower levels in JrDHN1 compared to WT. Expression levels of drought-related genes MYB, ADH, CAM showed an initial increase followed by a decrease trend, with significantly higher levels in the overexpressing JrDHN line compared to WT after 2 weeks. Conclusion The overexpressing JrDHN transgenic walnut seedlings exhibited superior phenotype, photosynthetic capacity, and antioxidant capacity under PEG-simulated drought stress compared to WT. Overexpression of JrDHN gene in walnut seedlings effectively enhanced the activity of antioxidant enzyme system, scavenged reactive oxygen species, reduced cell damage, thereby improving plant drought resistance. [Ch, 8 fig. 1 tab. 34 ref.] -
Key words:
- walnut /
- drought /
- JrDHN /
- overexpression /
- functional analysis
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表 1 qPCR引物
Table 1. qPCR primers
引物 序列(5′→3′) Actin-F ATGATGTCAAGGTTAAGGACTC Actin-R CACAATGATCTCAGCTCCG QJrDHN-F ATTCAGCTCACCGACGAACA QJrDHN-R CTCCTCATGCTGCTGCTTCT -
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