菌根真菌提高植物抗旱性机制的研究回顾与展望

菌根真菌与全世界约97%的维管植物具有广泛的共生关系。大量研究结果显示菌根植物相比于非菌根植物对于干旱胁迫具有更高的耐受性,说明菌根真菌在植物抗旱过程中发挥着重要作用。本文对近年来国内外在菌根真菌协助植物抵御干旱作用机制方面的研究进行了归纳和总结,主要包括在干旱胁迫下菌根真菌对植物生理学特性的影响机制、菌根真菌提高植物抗旱性的分子机制以及菌根真菌对植物次生代谢途径的影响机制等3个方面。当前菌根真菌增强植物抗旱性的生理机制方面的研究较为深入,而其他两个方面的研究则相对薄弱。随着分子生物学技术的发展,菌根真菌增强植物抗旱性的分子机制和涉及的相关代谢通路将被进一步揭示。本文旨在呈现菌根真菌提高植物抗旱性机制的研究前沿,为菌根互作更深层次的理论研究以及功能菌剂的研发提供一定的理论参考。     

内生真菌感染对干旱胁迫下黑麦草生长的影响

 内生真菌是生活在健康植物的茎叶内,形成不明显感染的一类真菌。以黑麦草（Lolium perenne L.）为实验材料,研究在不同强度的干旱胁迫下内生真菌（Neotyphodium lolii）侵染对其叶片延伸生长、分蘖数和生物量的影响。结果表明,与非感染种群相比,内生真菌感染对黑麦草叶片延伸速率无明显促进作用;内生真菌感染种群具有明显较多的分蘖数;在重度胁迫并经过恢复期后,内生真菌感染种群具有较高的根冠比。因而内生真菌可能通过提高植物的分蘖能力和促进有机物向根系的分配来促进宿主植物的营养生长并提高其抗旱性     

干旱胁迫下内生真菌感染对羽茅的生理生态影响

本研究在田间环境下对感染和未感染内生真菌的天然宿主羽茅（Achnatherum sibiricum (L. ) Keng）进行了干旱胁迫实验,结果发现在干旱胁迫下,内生真菌感染对宿主植物的营养生长、生物量累积和叶绿素含量都没有显著影响,但对宿主植株光系统II光化学效率（Fv/Fm）的维持产生了有利效应。同时,内生真菌感染缓解了宿主植物细胞膜的旱害程度,表现在与未感染植株相比,感染植株的丙二醛（MDA）含量显著降低,但内生真菌的感染并未促使宿主植物体内保护酶如超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性的增加,只是显著增加了类胡萝卜素的含量。因此我们推测在羽茅中,内生真菌对宿主植物的保护作用可能更多的体现在非酶系统上。     

干旱胁迫下内生真菌感染对黑麦草光合色素和光合产物的影响

以含有内生真菌的黑麦草 (L olium perenne L.)种子为材料 ,采用加热处理方式构建内生真菌非感染的黑麦草种群 ,通过比较内生真菌感染 (EI)和非感染 (EF)植株在正常条件下和干旱胁迫条件下叶片相对水分含量、叶绿素、可溶性糖和淀粉含量等指标的差异 ,探讨黑麦草 EI和 EF种群对干旱胁迫的适应性差异。结果表明 :在中度胁迫后期 ,EI植株叶片的 RWC显著高于 EF植株 ,即 EI植株的保水能力更强。轻度水分胁迫下 ,内生真菌感染可使其宿主植物的可溶性糖含量增加 ,以增强宿主的渗透调节能力 ,随着干旱胁迫强度的加大 ,内生真菌的这一增益效应不再起作用 ,此时 ,宿主植物将更多的光合产物——淀粉积累于体内 ,以度过不良环境。第 2年春天 EI和 EF种群的恢复生长情况进一步表明 ,经过中度干旱胁迫后 ,EI种群的恢复更为迅速。生物量的大小是植物种群净光合作用能力的直接体现 ,研究中在中度干旱胁迫条件下 ,黑麦草 EI种群的生物量显著高于EF种群 ,但从光合色素的变化来看 ,相同水分状况下 EI和 EF植株的 Chla、Chlb以及 Car的变化趋势比较接近 ,这说明内生真菌感染并未缓解干旱胁迫对光合色素的破坏 ,内生真菌可能通过其它途径来改善宿主植物的光合能力     

干旱胁迫下内生真菌感染对黑麦草叶内几种同工酶的影响

以内生真菌感染(endophyte-infected,EI)与不感染(endophyte-free,EF)的黑麦草(Lolium perenne L．)种子建立实验种群,分别对其施加长时间不同强度的干旱胁迫,通过比较黑麦草体内过氧化物酶(POD)、超氧化物歧化酶(SOD)、多酚氧化酶(PPO)活性及其同工酶谱的变化以探讨保护酶系统在内生真菌——植物共生体的抗旱性方面所作的贡献。研究结果表明,水分胁迫和内生真菌对黑麦草3种酶的影响不仅表现在总量上而且表现在同工酶的酶谱及各区带的酶活力上。就总酶活力而言,EI和EF植株中POD、SOD和PPO的活性均随着干旱胁迫强度的增加而增加,进一步将EI和EF植株的酶活力进行比较,发现与EF植株相比,EI植株中POD和PPO的活性相对较低,而SOD的活性相对较高。从同工酶的谱带数量和强弱来看,POD同工酶各区带活力均随干旱胁迫强度的增加而增加,EI植株叶片增加的幅度高于EF叶片,而且EI叶片在重度胁迫下出现了1条新带SOD同工酶各区带活力在EI叶片中有随干旱胁迫增加而增加的趋势,而在EF叶片中有些区带酶活力增强,有些区带酶活力减弱,且EI叶片在中度胁迫下出现了1条新带;PPO同工酶随干旱胁迫的增强,EI和EF叶片均表现为有些区带酶活力增强,有些区带酶活力减弱。总之,内生真菌的感染虽然没有显著提高宿主植物黑麦草POD、SOD和PPO的活性,但使宿主黑麦草对干旱胁迫的反应更为迅速,其中既包括POD、SOD等酶活力的迅速升高,也包括新酶带的产生。     

硅提高植物抗旱性的生理机制研究进展

干旱作为限制作物产量和品质的主要非生物胁迫之一,对全球社会、经济和生态造成巨大损失。在全球气候变化背景下,提高植物抗旱性的重要性日益突显。硅能够提高植物的抗旱性：外源硅的施用可以影响气孔导度,改变蒸腾速率,改善植物水分状况;通过调节气孔动力学、合成光合色素,促进光化学反应,从而改善光合作用;此外硅可通过渗透调节以平衡植物对矿质元素的吸收,以及调节抗氧化防御系统,减轻植物在干旱胁迫中的氧化损伤。总结了硅对干旱胁迫下植物水分利用、光合作用、矿质元素吸收、抗氧化系统、植物激素代谢等方面的作用及相关生理机制。建议未来从复合逆境胁迫、低硅积累植物等方面进一步揭示硅提高植物抗旱性的作用机制,从而为农林生态系统合理利用硅素来提高生产效率提供科学依据和理论基础。     

内生真菌及其对宿主植物生态适应性的影响

从植物-真菌的相互作用和植物体内微生态学的角度,综述近年来植物-内生真菌互作关系的研究进展,分析在生物和非生物环境因子胁迫下,植物内生真菌对宿主生态适应能力的影响及其可能的机制,特别强调将植物及其内生微生物作为一个整体研究的重要性,表明植物内生真菌作为一类重要的微生物资源,可以在增强植物的生态适应性,缓解全球气候变化对植物和人类的压力方面发挥其重要的作用,因而具有良好的应用前景。     

植物内生真菌化感作用的研究现状

植物内生真菌能产生酚类、萜类和生物碱类等多种类型的化感物质,它们在植物的生长发育、抗生物胁迫和非生物胁迫方面发挥重要作用。对植物内生真菌的化感作用及其所产生的化感物质进行了综述,并展望了其化感作用的应用前景。     

内生真菌提高禾草抗盐碱性研究进展

盐碱会导致植株生长缓慢,甚至抑制其正常发育,如何降低高盐和高p H对植物的不利影响,已成为农业持续发展的重大课题。近年来,内生和共生真菌对宿主植物在抗盐碱方面的有益作用也引起了研究人员的广泛关注。综述了内生真菌对宿主禾草植物抗盐碱性影响的研究成果,首先评述了内生真菌对宿主禾草在盐碱胁迫下种子萌发和生长发育影响表现在:提高种子发芽率;促进胚芽和胚根生长;提高宿主禾草的分蘖数、叶片数、株高、生物量、根冠比、成熟花序长度、种子数和种子产量。但也有感染内生真菌对宿主在盐胁迫下无促进作用的。其次,评述了内生真菌在减少禾草盐碱胁迫的原初盐害方面作用表现为:影响膜透性、提高光合作用、增加水分利用效率、改变营养代谢和离子毒害、影响植物激素代谢。最后综述了内生真菌在减少禾草次生盐害方面作用,内生真菌具有促进禾草分泌抗氧化剂、增加抗氧化酶活性、调节有机渗透物质的作用。系统的归纳了内生真菌与宿主禾草抗盐碱性相关研究成果,提出未来可能的研究问题和方向为后期的科研提供参考。     

内生真菌提高禾草抗盐碱性研究进展

盐碱会导致植株生长缓慢甚至抑制其正常发育,如何降低高盐和高p H对植物的不利影响,已成为农业持续发展的重大课题。近年来,内生和共生真菌对宿主植物在抗盐碱方面的有益作用也引起了研究人员的广泛兴趣。本综述评述了内生真菌对宿主禾草植物抗盐碱性影响的研究成果,首先评述了内生真菌对宿主禾草在盐碱胁迫下种子萌发和生长发育影响:表现在提高种子发芽率;促进胚芽和胚根生长;提高宿主禾草的分蘖数、叶片数、株高、生物量、根冠比、成熟花序长度、种子数和种子产量。但也有感染内生真菌对宿主在盐胁迫下无促进作用的。其次,评述了内生真菌在减少禾草盐碱胁迫的原初盐害方面作用:表现为影响膜透性、提高光合作用、增加水分利用效率、改变营养代谢和离子毒害、影响植物激素代谢。最后综述了内生真菌在减少禾草次生盐害方面作用,内生真菌具有促进禾草分泌抗氧化剂、增加抗氧化酶活性、调节有机渗透物质的作用。系统的归纳了内生真菌与宿主禾草抗盐碱性相关研究成果,提出未来可能的研究问题和方向为后期的科研提供参考。     

Effects of mycorrhizal infection on drought tolerance and recovery in safflower and wheat

The influence of arbuscular mycorrhizal fungi on drought tolerance and recovery was studied in safflower (Carthamus tinctorius L.) and wheat (Triticum aestivum L.). Plants were grown with and without the mycorrhizal fungus, Glomus etunicatum Becker & Gerd., in nutrient-amended soil under environmentally-controlled conditions to yield mycorrhizal and nonmycorrhizal with similar leaf areas, root length densities, dry weights, and adequate tissue phosphorus. When drought stress was induced, mycorrhizal infection did not affect changes in leaf water, osmotic or pressure potentials, or osmotic potentials of leaf tissue rehydrated to full turgor in either safflower or wheat. Furthermore, in safflower, infection had little effect on drought tolerance as indicated by the level of leaf necrosis. Mycorrhizal wheat plants, however, had less necrotic leaf tissue than uninfected plants at moderate levels of drought stress (but not at severe levels) probably due to enhanced phosphorus nutrition. To determine the effects of infection on drought recovery, plants were rewatered at a range of soil water potentials from –1 to –4 MPa. We found that although safflower tended to recover more slowly from drought after rewatering than wheat, mycorrhizal infection did not directly affect drought recovery in either plant species. Daily water use after rewatering was reduced and was correlated to the extent that leaves were damaged by drought stress in both plant species, but was not directly influenced by the mycorrhizal status of the plants.     

Interaction between fungal endophytes and environmental stressors influences plant resistance to insects

Neotyphodium coenophialum, an endophytic fungus that infects shoots of tall fescue (Festuca arundinacea), may protect its host from herbivory through production of alkaloids. Yet, the fungus can also modify plant resource allocation, regrowth dynamics, and drought tolerance, and these changes may also influence herbivores. We tested if N. coenophialum infection interacted with stress (drought or simulated herbivory) to modify plant resistance to insects. We assigned greenhouse plants to one of four treatments: 1) clipping at 3 cm above the soil surface, 2) drought stress during insect bioassays, 3) drought stress prior to insect bioassays, or 4) daily watering. Treatments were crossed with presence or absence of endophyte to give eight treatment combinations, and we assessed the performance of bird cherry‐oat aphid (Rhopalosiphum padi) and fall armyworm (Spodoptera frugiperda) feeding on plants in two separate experiments from each of the eight treatments. Aphids were placed into clip bags on leaf blades and allowed to reproduce parthenogenetically. Plant tissue was fed to third instar fall armyworm caterpillars until they molted into the fifth instar. Developmental time was recorded and larval growth was obtained gravimetrically. We also assessed total protein nitrogen (N) and loline alkaloids in plants.
Total protein N was unaffected by endophyte infection. In contrast, stress influenced total protein N, but its effect varied with endophyte infection. Uninfected plants that were clipped had higher total protein N; this trend was absent in infected plants. Plants in drought stress had lower N, but only if they were infected. Lolines were nearly absent from uninfected plants. In infected plants they tended to be higher in clipped plants. The effect of endophyte infection differed between the two insects: aphid reproduction was reduced by the endophyte, but endophyte infection enhanced caterpillar performance. Both insects were affected by interactions between the endophyte and stress. Aphids were negatively affected by drought stress, but only when feeding on uninfected plants, while caterpillars showed the opposite response, displaying lower performance on drought stressed plants only if they were infected. Aphids reproduced faster on regrowth tissue (following damage by clipping) of uninfected plants, but endophyte infection cancelled this effect. In contrast, performance of caterpillars was not influenced by an interaction between damage and infection. We conclude that N. coenophialum does not provide universal resistance to insects. Endophyte‐mediated resistance varies with insect species and will be a complex function of environmental stress, including drought and prior damage.     

Enhancing drought tolerance in C(4) crops

Adaptation to abiotic stresses is a quantitative trait controlled by many different genes. Enhancing the tolerance of crop plants to abiotic stresses such as drought has therefore proved to be somewhat elusive in terms of plant breeding. While many C(4) species have significant agronomic importance, most of the research effort on improving drought tolerance has focused on maize. Ideally, drought tolerance has to be achieved without penalties in yield potential. Possibilities for success in this regard are highlighted by studies on maize hybrids performed over the last 70 years that have demonstrated that yield potential and enhanced stress tolerance are associated traits. However, while our understanding of the molecular mechanisms that enable plants to tolerate drought has increased considerably in recent years, there have been relatively few applications of DNA marker technologies in practical C(4) breeding programmes for improved stress tolerance. Moreover, until recently, targeted approaches to drought tolerance have concentrated largely on shoot parameters, particularly those associated with photosynthesis and stay green phenotypes, rather than on root traits such as soil moisture capture for transpiration, root architecture, and improvement of effective use of water. These root traits are now increasingly considered as important targets for yield improvement in C(4) plants under drought stress. Similarly, the molecular mechanisms underpinning heterosis have considerable potential for exploitation in enhancing drought stress tolerance. While current evidence points to the crucial importance of root traits in drought tolerance in C(4) plants, shoot traits may also be important in maintaining high yields during drought.     

Mycorrhizal impact on drought stress tolerance of rose plants probed by chlorophyll a fluorescence, proline content and visual scoring

Micropropagated rose plants (Rosa hybrida L., cv. New Dawn) were inoculated with the arbuscular mycorrhizal (AM) fungus Glomus intraradices (Schenk and Smith) and subjected to different drought regimens. The dual objectives of these experiments were to investigate the mechanism and the extent to which AM can prevent drought damages and whether physiological analyses reveal enhanced drought tolerance of an economically important plant such as the rose. In a long-term drought experiment with four different water regimens, visual scoring of wilt symptoms affirmed that AM in a selected host–symbiont combination increased plant performance. This effect was mostly expressed if moderate drought stress was constantly applied over a long period. In a short-term experiment in which severe drought stress was implemented and plants were allowed to recover after 4 or 9 days, no visual differences between mycorrhizal and non-mycorrhizal roses were observed. Therefore, the early physiological steps conferring drought tolerance were prone to investigation. Proline content in leaves proved to be an unsuitable marker for AM-induced drought tolerance, whereas analysis of chlorophyll a fluorescence using the JIP test (collecting stress-induced changes of the polyphasic O-J-I-P fluorescence kinetics in a non-destructive tissue screening) was more explanatory. Parameters derived from this test could describe the extent of foliar stress response and help to differentiate physiological mechanisms of stress tolerance. AM led to a more intense electron flow and a higher productive photosynthetic activity at several sites of the photosynthetic electron transport chain. A K step, known as a stress indicator of general character, appeared in the fluorescence transient only in drought-stressed non-mycorrhizal plants; conversely, the data elucidate a stabilising effect of AM on the oxygen-evolving complex at the donor site of photosystem (PS) II and at the electron-transport chain between PS II and PS I. If drought stress intensity was reduced by a prolonged and milder drying phase, these significant tolerance features were less pronounced or missing, indicating a possible threshold level for mycorrhizal tolerance induction.     

丛枝菌根真菌通过上调根系及自身水孔蛋白基因表达提高玉米抗旱性

在模拟干旱条件下, 研究了接种丛枝菌根(AM)真菌Glomus intraradices对玉米(Zea mays)根部13种质膜水孔蛋白基因表达的影响, 同时观测了AM真菌自身水孔蛋白基因的表达情况。结果表明, 干旱条件下, 除Zm PIP1;3、Zm PIP1;4、Zm PIP1;5和Zm PIP2;2之外的接种处理能显著提高根部其他8种质膜水孔蛋白基因的表达(Zm PIP2;7表达量未检测出), 并且AM真菌菌丝中水孔蛋白基因GintAQP1表达也显著增强。与此同时, 接种处理明显改善了植物水分状况, 提高了叶片水势。AM真菌增强宿主植物根部及自身的水孔蛋白基因的表达对于提高植物抗旱性具有潜在的重要贡献。     

Additive and non-additive responses of seedlings to simulated herbivory and drought

Drought is a global threat, increasing in severity and frequency throughout tropical ecosystems. Although plants often face drought in conjunction with biotic stressors, such as herbivory or disease, experimental studies infrequently test the simultaneous effects of drought and biotic stress. Because multiple simultaneous stressors may have non-additive and complex effects on plant performance, it is difficult to predict plant responses to multiple threats from research examining one stress at a time. Using an experimental approach in the greenhouse, we investigated potential non-additivity in seedling growth and survival to simulated drought and herbivory across a phylogenetically diverse pool of ten Hawaiian plant species. Overall, seedlings showed limited tolerance, defined as similar growth and survival in stressed compared with control (non-stressed) plants, to simulated herbivory and drought, with the combined effects of both stressors to be generally additive and negative across species. Significant variation in stress tolerance was detected among species, and species variation was explained, at least in part, by functional traits such that species with larger root/shoot ratios and smaller seeds, tended to demonstrate greater herbivory and drought tolerance. Future research incorporating additional trait analysis and different stressors could shed light on mechanisms underlying seedling stress tolerance and clarify whether additivity, as detected in this study, extends across other combinations of stressors. Such work will provide needed insights into the regeneration of seedlings in tropical forests under threats of herbivory and climate change.     

植物水通道蛋白的干旱应答机制研究进展

干旱胁迫是严重影响全球作物生产的非生物胁迫之一,研究植物耐旱机制已成为一个重要领域。水通道蛋白是一类特异、高效转运水及其它小分子底物的膜通道蛋白,在植物中具有丰富的亚型,参与调节植物的水分吸收和运输。近10年来,水通道蛋白在植物不同生理过程中的作用,一直受到研究人员的关注,特别是在非生物胁迫方面,而研究表明水通道蛋白在干旱胁迫下对植物的耐旱性起着至关重要的作用,能维持细胞水分稳态和调控环境胁迫快速响应。水通道蛋白在植物耐旱过程中的调控机制及功能较复杂,而关于其应答机制和不同亚型功能性研究的报道甚少。该文综述了植物水通道蛋白的分类、结构、表达调控和活性调节,分别从植物水通道蛋白响应干旱表达调控机制、水通道蛋白基因表达的时空特异性、水通道蛋白基因的表达与蛋白丰度,水通道蛋白基因的耐旱转化四个方面阐明干旱胁迫下植物水通道蛋白的表达,重点阐述其参与植物干旱胁迫应答的作用机制,并提出水通道蛋白研究的主要方向。     

Different mechanisms of photosynthetic response to drought stress in tomato and violet orychophragmus

Carbonic anhydrase (CA) catalyzes reversible hydration of CO₂ and it can compensate for the lack of H₂O and CO₂ in plants under stress conditions. Antioxidative enzymes play a key role in scavenging reactive oxygen species and in protecting plant cells against toxic effects. Tomato represents a stress-sensitive plant while violet orychophragmus belongs to adversity-resistant plants. In order to study the drought responses in tomato and violet orychophragmus plants, CA and antioxidative enzyme activities, photosynthetic capacity, and water potential were determined in plants under drought stress. We found that there were similar change trends in CA activity and drought tolerance in violet orychophragmus, and in antioxidative enzymes and drought tolerance in tomato plants. Basic mechanisms of drought resistance should be identified for understanding of breeding measures in plants under stress conditions.