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干旱是植物生长、发育和生产力的主要环境制约因素。由于林木寿命长,难以大规模灌溉,干旱极大地降低了许多森林生态系统的树木生产力和存活率[1]。因此,加快对林木抗旱机制的剖析,提高林木对干旱的适应能力,是干旱土地利用、环境可持续性和提高经济效益的迫切需要。为了适应干旱胁迫,植物已经进化出复杂的机制来感知外部信号,并通过调节基因的表达来协调代谢途径和形态特征[2]。
AP2/ERF家族转录因子调控植物的多种发育过程,在激素调控和逆境应答中发挥重要作用[3]。AP2/ERF家族转录因子在高等植物中调控多种环境胁迫响应过程,如非生物胁迫(冷、热、旱、盐、渗透胁迫)和生物胁迫(食草昆虫和微生物病原体)[4-8]。此外,许多研究表明,过表达AP2/ERF家族转录因子的转基因植物对非生物和生物胁迫的耐受性有所提高[9-11]。例如,对ERF76转基因杨树(Populus simonii × Populus nigra)转录组测序中发现有16个上调转录因子基因和45个胁迫相关基因的表达,提高了ABA(脱落酸)和GA(赤霉素)的生物合成能力,从而增强了杨树对盐胁迫的耐受性[12]。新疆杨(Populus alba var. pyramidalis Bunge) PalERF109的过表达增强了杨树的耐盐性,进一步的分析表明,PalERF109直接上调了一个高亲和力K + 转运体(HKT)基因PalHKT1;2。表明PalERF109通过直接激活PalHKT1;2增强了耐盐性,并扩展了对ERF基因在树木胁迫反应中的作用的理解[13]。在盐和干旱胁迫下转基因ERF38过表达杨树过氧化物酶(Peroxidase, POD)、超氧化物歧化酶(Superoxide dismutase, SOD)、可溶性蛋白含量和脯氨酸含量显著增加,表明ERF38基因的过表达可以提高转基因杨树的耐盐和渗透性[14]。
胡杨(Populus euphratica Oliv.)是分布于我国西北沙漠地区沙漠河岸森林的优势树种,在维持当地沙漠生态系统方面发挥着重要的作用[15]。由于其对极端恶劣环境的良好适应性,胡杨被认为是木本植物非生物胁迫耐受机制研究的典型模式物种[16]。前期通过对胡杨种子耐盐全基因组关联分析(Genome wide association study, GWAS)和转录组分析中获得胡杨PeERF1基因[17],通过亚细胞定位实验发现PeERF1为核定位蛋白,转录自激活实验证明PeERF1基因具有转录自激活活性。耐盐能力分析试验证明胡杨PeERF1基因能够增加转基因植株的耐盐性[18],但其耐旱机制中的作用尚缺乏研究。本研究为探明胡杨PeERF1基因应答干旱胁迫的表达特点,以胡杨为材料研究PeERF1基因在模拟干旱胁迫(PEG)下不同组织的时空表达模式。通过对野生型银腺杨(Populus alba × P. glandulosa ‘84k’, ‘84K’杨)、转PeERF1基因过表达和抑制表达银腺杨进行模拟干旱胁迫,观察PeERF1基因在模拟干旱胁迫下表达模式、表型和生理指标的变化,为进一步探究该基因在植物抗逆中的功能提供依据。
胡杨PeERF1基因提高转基因银腺杨84K耐旱性研究
Improvement of Drought Tolerance of PeERF1 Transgenic Populus alba × Populus glandulosa ‘84K’
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摘要:
目的 分析PeERF1基因在胡杨干旱胁迫下的作用和PeERF1转基因植株抗旱的生理适应机制,为进一步研究该基因在木本植物中的抗旱调控机制奠定基础。 方法 以胡杨为材料进行20% PEG6000模拟干旱(0、12和24 h)处理,对胡杨PeERF1基因进行时空表达模式分析。以非转基因(WT)、过表达35S::PeERF1转基因植株(PE)、显性抑制35S::PeERF1-SRDX转基因植株(SE)为试验材料,采用不同浓度PEG6000(对照组,20%)处理WT、PE和SE模拟干旱胁迫,并对其进行表达模式、生长性状和生理指标分析。 结果 研究结果表明PeERF1基因在胡杨叶中的表达水平最高,其次是茎和根。在正常状态下,转基因植株和WT生长性状、叶绿素含量、过氧化氢酶(CAT)、丙二醛(MDA)和过氧化物酶(POD)含量变化不大。在20%PEG6000处理后,PE转基因植株比WT表现出更好的生长状态,PE转基因植株的叶绿素含量、CAT和POD含量高于WT,PE转基因植株MDA含量低于WT。而SE转基因植株则表现出相反的性状。 结论 本研究结果初步显示干旱胁迫下,PeERF1基因转基因植株生长状态、叶绿素含量、过氧化氢酶、丙二醛和过氧化物酶等相关生理指标均发现显著变化。PeERF1对转基因杨树响应干旱起到了正向调控的作用。 Abstract:Objective This study aimed to analyze the role of PeERF1 gene under drought stress in Populus euphratica, and evaluate the physiological adaptation mechanism of PeERF1 transgenic ‘ 84k’ (Populus alba × Populus glandulosa ‘84k’) to drought resistance for providing insights into further study of the drought resistance regulation mechanism of this gene in woody plants. Methods The drought (0, 12 and 24 h) treatment simulated with 20% PEG6000 was carried out on P. euphratica to analyze the temporal and spatial expression pattern of the PeERF1. Based on non-transgenic (WT), overexpressing 35S::PeERF1 transgenic plants (PE), and dominantly suppressed 35S::PeERF1-SRDX transgenic plants (SE), WT, PE and SE were treated with different concentrations of PEG-6000 (Control and 20%) to simulate drought stress, and analyzed for growth traits and physiological indicators. Results The results showed that the expression level of PeERF1 gene was the highest in leaves of P. euphratica, followed by stems and roots. Under normal conditions, the transgenic plants and the WT showed little change in growth traits, chlorophyll content, catalase (CAT), malondialdehyde (MDA) and peroxide dismutase (POD) content. Under 20% PEG6000 treatment, the PE transgenic plants showed better growth status, and higher chlorophyll content, CAT and POD content than WT, and the PE transgenic plants showed lower MDA content than WT, while the SE transgenic plants showed opposite traits. Conclusion Under drought dress, significant changes are found in the growth status, chlorophyll content, catalase, malondialdehyde and peroxidase related physiological indicators of transgenic plants. PeERF1 plays a positive regulatory role on transgenic P. alba × P. glandulosa ‘84k’ in response to drought. -
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