植食性昆虫对植物的反防御机制

本文综述了植食性昆虫对植物的反防御机制.一方面,植食性昆虫可通过其快速进化的寄主选择适应性,改变取食策略,调节生长发育的节律,以及规避自然天敌等抑制、逃避或改变植物的防御,即行为防御机制;另一方面,植食性昆虫可适应植物蛋白酶抑制剂、逃避植物防御伤信号、解毒植物次生物质,以及抑制植物阻塞反应来对植物防御进行反防御,即生理和生化防御机制.其中,昆虫抑制植物伤信号,防止植物阻塞反应是反防御机制的研究热点.昆虫反防御的研究有助于提高对昆虫-植物间协同进化关系的认识,并为害虫治理和抗虫植物的培育提供新的思路.     

取食十字花科植物的植食性昆虫与寄主植物硫苷的互作

十字花科植物含有硫苷-黑芥子酶防御系统,也被称作"芥子油炸弹",是目前研究最多的植物防御机制。硫苷和黑芥子酶分开储存在不同的植物细胞中,当植物受到昆虫取食、病原微生物侵害、机械损伤等危害时,植物体内的黑芥子酶与硫苷结合,催化其产生有毒的水解产物——异硫氰酸酯(isothiocyanate,ITC)、腈类化合物(nitrile)和其他活性物质等,从而避免或者减少植物受到损害。然而在长期的协同进化过程中,十字花科蔬菜害虫也具有了相应的反防御机制才能够适应寄主。这种反防御机制根据硫苷种类的不同,也具有多样性,且不仅表现在十字花科广食性和寡食性昆虫之间,还表现在广食性和寡食性昆虫之内。本文综述了十字花科植物硫苷类型、硫苷-黑芥子酶防御体系和害虫诱导的植物硫苷防御反应,并从不同十字花科蔬菜害虫如何代谢、隔离、利用和转运硫苷等方面讨论了害虫的反防御机制,以期为研究十字花科蔬菜害虫与寄主植物协同进化提供借鉴和参考。     

虫害诱导植物间接防御反应的激发与信号转导途径

植物通过产生和释放挥发性物质增加植食性昆虫的天敌对其寄主或猎物的定位，减少植食性昆虫对植物的取食，从而达到间接防御的目的。植物对植食性昆虫所做出间接防御反应激发因子和信号转导途径的研究，对应用虫害诱导植物挥发物引诱害虫天敌，并进一步从植物、植食性昆虫及其天敌间三级营养关系，研究动植物协同进化机理和病虫害防治具有深远意义。本文根据国内外最新研究进展，对虫害诱导植物间接防御反应的激发因子，昆虫取食信号的转导途径及对植物间接防御相关基因的激活等方面进行了系统地综述。     

蒙古沙冬青对灰斑古毒蛾重复取食响应的代谢组学分析

植物对同种昆虫重复取食做出更有效的响应是植物适应自然界虫害周期性爆发的重要策略。为了研究蒙古沙冬青对其主要害虫灰斑古毒蛾幼虫重复取食响应的代谢基础,本实验采用基于核磁共振（NMR）的代谢组学技术,分析了遭受同一年不同代灰斑古毒蛾幼虫取食的蒙古沙冬青叶片和对照组幼苗叶片的代谢差异。结果表明,仅遭受第一代幼虫取食叶片在第二代幼虫期与对照之间代谢物存在较小差异,而仅遭受第二代幼虫取食叶片与遭受两代幼虫取食叶片代谢差异显著,仅遭受第一代与仅遭受第二代幼虫取食的植株相邻分枝叶片差异显著。另外,只有仅遭受第二代幼虫取食组幼苗表现出处理叶片与相邻分枝叶片的显著代谢差异,并且这种代谢差异为总体代谢的变化,而并未表现为特定代谢物含量变化。由此可见,蒙古沙冬青能在代谢水平以很小的代谢变化来保存昆虫取食信息,在遭受同种昆虫取食后,代谢差异被放大,而且这种信息保存在遭受取食叶片中表现更明显。     

昆虫与植物的协同进化:寄主植物-铃夜蛾-寄生蜂相互作用

近数10年内,Ehrlich和Raven于1964年提出的协同进化理论及Jermy于1976年提出的顺序进化理论极大地促进了对昆虫与植物相互作用的研究。文章首先简要介绍有关理论,对植食性昆虫与植物关系研究的若干核心问题进行评述。主要问题包括(1)植食性昆虫如何选择寄主植物?(2)植物次生物质是否作为植物防御昆虫取食的重要屏障?(3)昆虫能否适应植物的化学防御?(4)植食性昆虫寄主范围是否是从广到专演化的?随之,作者结合对铃夜蛾Helicoverpa系统研究取得的结果,对上述问题做了进一步的论证和阐述。最后,在继承协同进化、顺序进化等理论精髓的基础上,根据当今三营养级相互作用领域的研究新进展,提出一个新的假说,即多营养级协同进化假说。该假说肯定植物次生物质在植物防御和昆虫识别寄主植物上的重要作用,同时把其他营养级并列放入交互作用的系统,特别强调第三营养级在昆虫与植物关系演化过程中的参与和寄主转移与昆虫食性专化和广化的联系。     

昆虫取食诱导的植物防御反应

植物被昆虫取食后可产生直接防御或间接防御。直接防御通过增加有毒的次生代谢产物或防御蛋白对昆虫生理代谢产生不利的影响,但对植物的消耗较大。间接防御通过释放挥发性化合物吸引天敌昆虫,并以此控制植食性昆虫。特异性的昆虫激发子(insect specific elicitors)能够诱导挥发性化合物的释放。多种信号途径参与昆虫取食诱导的植物防御反应,它们之间的相互作用协同或拮抗。了解昆虫取食诱导的植物防御反应,对于害虫综合治理策略的完善具有重要的意义。     

植物与植食性昆虫相互作用的分子机制

在长期的协同进化中,植物建立起应对昆虫取食为害的精密而又复杂的防御机制,植物转录组调控中防御应答基因的表达及防御物质的合成因不同的昆虫取食方式而异。一般来说,咀嚼式口器昆虫取食时造成大面积组织伤害,可诱导植物产生伤害反应;而刺吸式口器昆虫因其特殊的口针取食,诱导植物激活病原体相关的防御途径。不同的防御途径激活不同的识别机制和信号途径。本文从信号识别和转导上综述了不同食性的昆虫取食植物时所引发的防御反应,分析了昆虫-植物相互作用关系的分子机制。     

韧皮部取食昆虫诱导的植物防御反应

刺吸式昆虫与寄主植物之间具有特殊的生物互作关系。本文对刺吸式昆虫取食韧皮部诱导的植物防御反应类型、 防御物质变化、 信号途径以及植物反应转录组学研究等方面进行综述。韧皮部取食昆虫取食诱导的植物防御反应机制主要包括： (1)改变自身的营养状况; (2)产生有毒的次生化合物; (3)产生防御蛋白。防御反应与植物水杨酸、 茉莉酸、 乙烯等信号分子密切相关。研究表明, 刺吸式昆虫取食诱导的植物防御反应主要引发以水杨酸为主的信号途径, 但相关分子互作机制还有待明确。日益丰富的基因组资源和不断发展的分子生物学技术为揭示植物防御反应中信号分子的作用机制、 找出植物内生抗性的特异因子以及阐明诱导防御机制奠定了基础。了解刺吸式昆虫取食诱导的植物防御反应, 为深入理解植物-昆虫间协同进化关系提供了依据, 为害虫治理和抗虫植物的培育提供了新的思路。     

植物蛋白酶抑制素抗虫作用的研究进展

植物自身为抵抗昆虫等的为害,在长期进化过程中形成了复杂的化学防御体系,其中起主导作用的是一些植物化学物质。这些化合物能影响昆虫（或其它有机体）的生长、行为和群体生物学,因而又称为它感素（allelochemics）[1～3]。大多数它感素为植物的利己素,可以单一或协同对害虫起作用,构成植物的抗虫性。根据植物对昆虫取食的反应,可将植物的化学防御概括为两类：一类是组成型防御[4],即抗虫物质不依赖于昆虫的取食而存在于植物组织中;另一类是诱导型防御[5～9],即植物仅当昆虫取食时才大量合成抗虫物质。诱导型抗虫物质当然亦可以组…     

寄生蜂抗药性研究进展

植物-植食性昆虫-寄生蜂三级营养结构之间由于长期相互适应和协同进化,产生了一系列独特的相互关系。选择压力将对害虫和寄生蜂的抗药性演化产生影响,但由于寄生蜂具有与植食性昆虫不同的生物学及生态学特性,选择压力对害虫和寄生蜂抗药性演化的影响作用也是不同的。研究结果表明,除体外杀虫剂对寄生蜂的直接汰选因素外,进入寄主昆虫体内的杀虫剂成分、寄主昆虫取食不同植物的特有成分以及气候因子等均会对寄生蜂的抗药性演化产生影响。     

Leaf mines as visual defensive signals to herbivores

Leaf‐mining insects produce conspicuous and distinct leaf mines on various types of plant leaves. The diversity of leaf‐mine morphology has typically been explained by several factors, such as selective feeding on plant tissues, improvement of microclimate, faecal disposal, reduction in the efficiency of parasitoid search behaviour and leafminer phylogeny. Although these factors are certainly associated with mining patterns, masking the mines, rather than making them conspicuous, appears to be more advantageous for deterring parasitoids and predators of leafminers. However, here, I propose that prominent leaf mines may serve to signal or cue herbivores to avoid feeding on the mined leaves. Because most leafminers are sessile and complete their development within a single leaf, herbivory of mined leaves is detrimental to leafminer survival. Other herbivores appear to avoid consuming mined leaves for a variety of reasons: leaf mines mimic leaf variegation or mottling; mined leaves induce chemical and physical defences against herbivores; and leaf mines mimic fungal infection, animal excrement, and necrosed plant tissues. Hence, natural selection may have favoured leafminers that produce conspicuous mines because of the increased survival and fecundity of thereby reducing herbivory on mined leaves.     

多食性斑潜蝇对寄主植物的选择

综述了有关斑潜蝇对寄主植物选择的研究进展。斑潜蝇对寄主植物的选择表现为对植物组织的选择、对植物不同部位叶片的选择、对同种植物不同品种的选择、对不同寄主植物的选择四个方面。斑潜蝇对寄主植物的选择主要受叶表面的物理性质、植物叶的化学物质成分、成长经历等因素的影响。阐述了多食性斑潜蝇寄主植物范围扩大的原因。     

Fungal endophytes and phytochemistry of oak foliage: determinants of oviposition preference of leafminers?

Sedentary insect herbivores, such as gallformers and leafminers, are usually non-randomly distributed among and within host plants. Dispersion of these insects is largely a function of female oviposition choice. In field experiments and observations spanning two growing seasons, we tested the hypothesis that selective oviposition on individual leaves within trees by the dominant herbivore of Emory oak, the monophagous leaf-miner Cameraria sp. nov., is determined by the probability of colonization by endophytic fungi. These fungi are alleged to act as plant mutualists by deterring, killing, or inhibiting the growth of insect herbivores. We found that leaves selected by females for oviposition and paired, unmined leaves were equally likely to be colonized by fungal endophytes. Furthermore, condensed and hydrolyzable tannin levels, purported inhibitors of fungal infection, and protein content did not vary between leaves selected by females and unmined leaves, or between leaves with and without endophyte infections. We conclude that female Cameraria do not choose leaves within trees for oviposition on the basis of propensity for endophytic fungal infection or on phytochemical parameters that might indicate probability of future infections. At this spatial scale at least, fungal endophytes do not explain the highly aggregated distribution of Cameraria among leaves and associated costs in terms of increased larval mortality. Fungal endophytes may, nevertheless, affect leafminer dispersion and abundance at larger spatial scales, such as host plant populations or species. We did find, however, that the amount of mining activity on leaves is positively associated with increased colonization by fungal endophytes. We suggest that mining activity increases endophyte fungal infections by facilitating spore germination and hyphal penetration into the leaf or by altering leaf phytochemistry. The facilitation of endophyte colonization by leafmining activity coupled with the lack of predictability of endophyte infections based on leaf phytochemistry and almost 100% infectivity of all oak leaves during sporadic wet years may prevent female leafminers from discriminating leaves for oviposition on the basis of current or future levels of endophytes in leaves.     

Leaf miners: The hidden herbivores

Leaf mining is a form of endophagous herbivory in which insect larvae live and feed within leaf tissue. In this review we discuss aspects of leaf miner ecology, and the current evidence for three hypotheses relating to the evolution of this feeding guild. We also present a summary of the literature coverage relating to these herbivores, which have been relatively poorly studied compared with insects that feed externally such as sap suckers and leaf chewers. The majority of published studies concern leaf miners from the northern hemisphere, with a general focus on those species considered to be agricultural, forestry or horticultural pests. In a more detailed case study, we examine aspects of leaf miner ecology of Australian species. At least 114 species have been recorded as leaf miners in Australia in four orders: Coleoptera, Lepidoptera, Diptera and Hymenoptera. Lepidoptera and Diptera are the most speciose orders of Australian leaf miners; Hymenoptera are represented by a single endemic genus and half of all coleopteran miners are species introduced for biological control. Both the known number of leaf‐mining species in Australia and the known number of hosts have increased in recent years following new targeted surveys. Leaf miners in Australia occur in many habitats and feed on a wide variety of host plants in at least 60 families although most individual species are monophagous. Although much of the research on leaf miners in Australia has focused on species that are commercially important pests or biological control agents, studies on fundamental aspects of leaf miner ecology are increasing. We identify a number of research questions aimed at better understanding the ecology of leaf miners in Australia and elsewhere.     

Oviposition,larval survival and leaf damage by the willow leaf blotch miner,Micrurapteryx salicifoliella,in relation to leaf trichomes across 10 Salix species

1. Foliar trichomes clearly reduce chewing damage and efficiency of movement by some insect herbivores, but the effect of trichomes on insect oviposition is less well characterised. Trichomes are likely to have particularly strong, negative effects on species that require secure attachment of the egg to the leaf epidermis for successful transition to the feeding stage – a group that includes many leaf mining insects. 2. One such species, Micrurapteryx salicifoliella, must initially enter leaf cells directly from an egg adhered to the cuticle, but later instars can move between leaves and initiate new mines from the leaf exterior. 3. Natural patterns of occurrence by M. salicifoliella were quantified on 10 sympatric Salix species varying in trichome expression to test whether trichomes were associated with reduced oviposition, larval survival and leaf damage. 4. Mean egg density and leaf mining damage were negatively related to mean trichome density across Salix species. Survival of M. salicifoliella from egg to pupa was positively related to trichome density, suggesting that initiation of new mines by late‐instar larvae was not adversely affected by trichomes. There was no evidence that trichomes benefited leaf miner larvae indirectly by decreasing density‐dependent mortality; rather, the positive relationship between trichome density and larval survival may reflect less effective chemical defence by Salix species expressing high trichome density. 5. The results suggest that foliar trichomes serve as an effective defence against M. salicifoliella by deterring oviposition, but do not reduce the survivorship of those individuals that successfully transition from egg to larva.     

Oviposition by herbivorous insects induces changes in optical and mechanical properties of <Emphasis Type="Italic">Prunus avium</Emphasis> leaves

This study of animal–plant interaction focused on the impact of oviposition by an insect on the leaves of Prunus avium (cherries). We examined whether the oviposition by Caliroa cerasi affects leaf mechanical and spectral traits in P. avium. Three cultivars of P. avium were studied. Infested leaves had from 1 to 18 eggs and exhibited higher leaf dry mass per area (LMA) than leaves without eggs. Leaf dry weight and LMA were positively correlated with egg number per leaf. Infested leaves tended to have higher number of trichomes. Leaf thickness and material and structural resistance tended to increase in infested leaves. The reflectance across all wavelengths (500–700 nm) in leaves with larger number of eggs was higher compared to leaves without eggs. Photosynthetic performance was reduced and oxidative activity was increased in leaves with eggs. Extrafloral nectaries increased with increasing the number of eggs per leaf and thus play an important role in defense against herbivores by providing nectar rewards that attract their depredators. These responses to oviposition may be beneficial for the plants in terms of resistance to feeding larvae.     

Molecular phylogenetics of the holly leafminers (Diptera: Agromyzidae: Phytomyza): species limits, speciation, and dietary specialization

A molecular phylogenetic analysis was conducted to determine relationships and to investigate character evolution in the Phytomyza ilicis group of leafmining flies on hollies (Aquifoliaceae: Ilex). A total of 2207 bp of the mitochondrial cytochrome oxidase I and II genes were sequenced for all known holly leafminers, as well as for several undescribed members of this group. Maximum-parsimony analysis of the sequence data indicates that these leafminers form a monophyletic group with the inclusion of an undescribed leafminer that feeds on the distantly related plant Gelsemium sempevirens (Loganiaceae). Species boundaries of previously known and of undescribed holly leafmining species were confirmed with the molecular data, with one exception. Optimization of variable ecological and morphological characters onto the most parsimonious phylogeny suggests that these traits are evolutionarily labile, requiring multiple instances of convergence and/or reversal to explain their evolutionary history. Speciation in holly leafminers is associated with host shifts and appears to involve colonization of new hosts more often than cospeciation as the hosts diverge. Monophagy is the most common feeding pattern in holly leafminers, and more generalized feeding is inferred to have evolved at least two separate times, possibly as a prelude to speciation.     

Feeding damage by larvae of the mustard leaf beetle deters conspecific females from oviposition and feeding

Herbivorous insects may be informed about the presence of competitors on the same host plant by a variety of cues. These cues can derive from either the competitor itself or the damaged plant. In the mustard leaf beetle Phaedon cochleariae (Coleoptera, Chrysomelidae), adults are known to be deterred from feeding and oviposition by the exocrine glandular secretion of conspecific co-occurring larvae. We hypothesised that the exocrine larval secretion released by feeding larvae may adsorb to the surface of Chinese cabbage leaves, and thus, convey the information about their former or actual presence. Further experiments tested the influence of leaves damaged by conspecific larvae, mechanically damaged leaves, larval frass and regurgitant on the oviposition and feeding behaviour of P. cochleariae. Finally, the effect of previous conspecific herbivory on larval development and larval host selection was assessed. Our results show that (epi)chrysomelidial, the major component of the exocrine secretion from P. cochleariae larvae, was detectable by GC-MS in surface extracts from leaves upon which larvae had fed. However, leaves exposed to volatiles of the larval secretion were not avoided by female P. cochleariae for feeding or oviposition. Thus, we conclude that secretion volatiles did not adsorb in sufficient amounts on the leaf surface to display deterrent activity towards adults. By contrast, gravid females avoided to feed and lay their eggs on leaves damaged by second-instar larvae for three days when compared to undamaged leaves. Mechanical damage of leaves and treatment of artificially damaged leaves with larval frass or regurgitant did not affect oviposition and feeding of P. cochleariae. Since no adverse effects of previous herbivory on larval development were detected, we suggest that female P. cochleariae avoid Chinese cabbage leaves damaged by feeding larvae for other reasons than escape from competition or avoidance of direct negative effects that result from consuming induced plant material.     

南美斑潜蝇寄主选择性与植物次生化合物及叶毛的关系

采用非自由选择法,以刺伤孔（包括取食孔和产卵孔）数为指标,在室内测定了南美斑潜蝇对6科、16种、22个蔬菜品种的寄主选择性。结果表明,南美斑潜蝇对供试蔬菜品种的选择性存在显著差异,选择性大小依次为豆科>菊科>葫芦科>茄科>伞形科>十字花科; 菜豆和茼蒿是南美斑潜蝇最喜欢产卵和取食的寄主,而甘蓝和番茄是其选择性最差的寄主。化学分析和解剖镜观察表明,叶片单宁酸、黄酮含量及叶毛密度在供试品种间存在显著差异： 苦瓜的单宁酸含量最高,其次为豌豆、番茄和青椒,含量最低的为金丝搅瓜、茼蒿、菜豆和美国西芹; 黄酮含量最高的为甘蓝和番茄,其次为苦瓜,最低为茼蒿、菜豆和美国西芹; 南瓜和小白菜的叶毛密度最高,其次为西葫芦、金丝搅瓜和甘蓝,最低为青椒、莴苣和苦瓜。相关分析表明,南美斑潜蝇寄主选择性与叶片单宁酸和黄酮含量呈显著的负相关关系,相关系数分别为-0.4425（ P=0.0392）和 -0.5728（ P=0.0053）,而与叶毛密度相关关系不显著（ R＝-0.1807,P=0.4211）。说明黄酮和单宁酸对南美斑潜蝇产卵和取食具有明显的抑制作用。     

Oviposition site selection by a lepidopteran leafminer in response to heterogeneity of leaf surface conditions: structural traits and microclimates

1. Leafminer larvae are sedentary and make feeding tracks called mines. Their spatial distribution in trees affects their growth and survival through interaction with the heterogeneity of environments, such as leaf traits and microclimate. Lepidopteran leafminers that mine lower leaf surfaces have shown evolutionary radiation, suggesting that lower surfaces improve leafminer performance. 2. The lepidopteran multivoltine leafminer Phyllocnistis sp. Zeller (Gracirallidae: Phyllocnistinae) uses the Japanese privet Ligustrum japonicum Thunb. (Oleaceae). It mines only the lower‐surface epidermal layer of primary shoot leaves early in the occurrence season, but once lammas shoots appear, which happens in seasons other than spring, it preferentially uses the lower surface, but also uses the upper surface of the leaves. This study examined whether selection of oviposition sites was associated with the structural traits and microclimate of the leaf surface. 3. The shift of oviposition site from primary to lammas shoot leaves followed increasing hardness and epidermal cell wall thickness of primary shoot leaves during leaf development, and mine initiation rates decreased below 20% after oviposition on mature primary shoot leaves. Preference for the lower surface was related to the thinner cuticle. However, the thinner cuticle of the upper surface on lammas shoot leaves allowed Phyllocnistis sp. to expand its mining sites to both surfaces with no decrease in mine initiation and emergence rates. 4. Microclimates (leaf surface and mine temperatures) did not differ between upper and lower surfaces, suggesting that microclimate did not affect oviposition site selection by Phyllocnistis sp. These results suggest that the adaptive radiation of lower‐surface mining may have been influenced by the leaf surface characteristics.