Protective and defensive roles of non-glandular trichomes against multiple stresses:structure-function coordination

As superficial structures,non-glandular trichomes,protect plant organs against multiple biotic and abiotic stresses.The protective and defensive roles of these epidermal appendages are crucial to developing organs and can be attributed to the excellent combination of suitable structural traits and chemical reinforcement in the form of phenolic compounds,primarily fl avonoids.Both the formation of trichomes and the accumulation of phenolics are interrelated at the molecular level.During the early stages of development,non-glandular trichomes show strong morphological similarities to glandular ones such as the balloon-like apical cells with numerous phenolics.At later developmental stages,and during secondary wall thickening,phenolics are transferred to the cell walls of the trichomes.Due to the diff use deposition of phenolics in the cell walls,trichomes provide protection against UV-B radiation by behaving as optical fi lters,screening out wavelengths that could damage sensitive tissues.Protection from strong visible radiation is also aff orded by increased surface light refl ectance.Moreover,the mixtures of trichome phenolics represent a superfi-cial chemical barrier that provides protection against biotic stress factors such as herbivores and pathogens.Although the cells of some trichomes die at maturity,they can modulate their quantitative and qualitative characteristics during development,depending on the prevailing conditions of the external biotic or abiotic environment.In fact,the structure and chemical constituents of trichomes may change due to the particular light regime,herbivore damage,wounding,water stress,salinity and the presence of heavy metals.Hence,trichomes represent dynamic protective structures that may greatly aff ect the outcome of many plant–environment interactions.

BrrTCP4b interacts with BrrTTG1 to suppress the development of trichomes in Brassica rapa var. rapa

The number of trichomes significantly increased in CRISPR/Cas9-edited BrrTCP4b turnip(Brassica rapa var.rapa)plants.However,the underlying molecular mechanism remains to be uncovered.In this study,we performed the Y2H screen using BrrTCP4b as the bait,which unveiled an interaction between BrrTCP4b and BrrTTG1,a pivotal WD40-repeat protein transcription factor in the MYB-bHLH-WD40(MBW)complex.This physical interaction was further validated through bimolecular luciferase complementation and co-immunoprecipitation.Furthermore,it was found that the interaction between BrrTCP4b and BrrTTG1 could inhibit the activity of MBW complex,resulting in decreased expression of BrrGL2,a positive regulator of trichomes development.In contrast,AtTCP4 is known to regulate trichomes development by interacting with AtGL3 in Arabidopsis thaliana.Overall,this study revealed that BrrTCP4b is involved in trichome development by interacting with BrrTTG1 in turnip,indicating a divergence from the mechanisms observed in model plant A.thaliana.The findings contribute to our understanding of the regulatory mechanisms governing trichome development in the non-model plants turnip.

Cloning and Expression Analysis of <i>TTG</i>1 Gene Related to <i>Rosa rugosa</i>Trichomes Formation

The TTG1 transcription factor plays an important role in the formation of plant trichomes. Based on the R. rugosa transcriptome data, this study cloned a R. rugosa TTG1 gene, named RrTTG1, and carried out bioinformatics analysis and fluorescence quantitative analysis to explore the relationship between TTG1 gene and R. rugosa trichomes formation, in order to lay a good foundation to cultivate a thornless plant in the family Rosaceae. In this experiment, six hybrid cultivars of R. rugosa “Zizhi”, R. rugosa “Xizi”, R. rugosa “Tang fen”, R. rugosa “Hun chun”, R. rugosa “Zi long wo chi” and R. rugosa “Tian e huang” were used as experimental materials, and the cDNA full length of this gene was obtained by RT-PCR and RACE, and the full length of the cDNA was 1348 bp. After bioinformatics analysis, it is predicted that its molecular formula is C1723H2661N465O529S12, the molecular weight is 38.71 KB, and the isoelectric point is 5.00. Its instability index is 54.30, which belongs to unstable protein;and its hydrophilic amino acid distribution is relatively uniform, and the amount is larger than hydrophobic amino acid, which belongs to hydrophilic protein. Phylogenetic tree was constructed for the TTG1 gene. Evolutionary analysis indicated that RrTTG1 is closely related to the TTG1 protein of Rosaceae family, and has a close relationship with other families. The expression analysis showed that the expression of RrTTG1 protein was negatively correlated with the trichome content of R. rugosa stems and leaves. The expression levels of the three spiny varieties of R. rugosa “Hun chun”, R. rugosa “Xizi” and R. rugosa “Zi long wo chi” were lower, and the expressions of the three less thorn varieties of R. rugosa “Zizhi”, R. rugosa “Tian e huang” and R. rugosa “Tang fen” were higher. According to the above results, it was speculated that RrTTG1 is involved in the synthesis of R. rugosa trichomes and belongs to the negative regulation mechanism.

Leaf Traits and Histochemistry of Trichomes of Conocarpus lancifolius a Combretaceae in Semi-Arid Conditions

Leaf traits, structure and water status of Conocarpus lancifolius, a Combretaceae were investigated under semi-arid conditions. The leaf traits examined included leaf area and thickness, stomatal distribution, sclerophylly, succulence and relative water content. Additionally, the types of secretory structures, histochemistry of trichomes, and chemical nature of the cuticlular waxes were evaluated. Leaves showed xerophytic characteristics including a high degree of sclerophylly, thick cuticle and outer epidermal cell wall, low relative water content and high trichome density on younger leaves. The species has two types of trichomes;a secretory, short-stalked capitate trichome and a non-secretory trichome with a bulbous base and a pointed tip. The leaves also have a pair of extrafloral nectaries on both sides of the distal end of the petiole, 3-4 pairs near the leaf apex and two secretory ducts or cavities on mature leaves that secreted polysaccharides, epicuticlar waxes and polyphenols. Compared to young leaves mature leaves had almost 3 times total cuticular wax deposit or load. The most abundant fatty acids were palmitic, stearic, nondecanoic, behenic and arachidic acids. The leaf traits and structures are discussed in relation to semi-arid habitat.

Localization of a defensive volatile 4-hydroxy-4-methylpentan-2-one in the capitate glandular trichomes of Oenothera glazioviana

Glandular trichomes of plants produce a wide variety of secondary metabolites which are considered as major defensive chemicals. The capitate glandular trichomes of Oenothera glazioviana(Onagraceae) were collected with laser microdissection and analyzed by gas chromatography-mass spectrometry. The volatile compound 4-hydroxy-4-methylpentan-2-one(1) was identified. We found that compound 1 displays antimicrobial, insecticidal, and phytotoxic activities. These results suggest that compound 1 might function as a defensive compound in the capitate glandular trichomes of O. glazioviana against pathogens, insect herbivores, and presumably competitive plants as well.

A Systematic Revision of the Genus Plectranthus L. (Lamiaceae) in Saudi Arabia Based on Morphological, Palynological, and Micromorphological Characters of Trichomes

This study aims to investigate the morphology and ultrastructure characters of pollen grains and trichomes in order to evaluate their systematic value of these characters in specific and intraspecific separation of the Saudi Arabian Plectranthus species. A critical systematic revision of 7 species of Plectranthus (Lamiaceae) in Saudi Arabia was conducted by means of numerical analyses based on thirty-one morphological characters, including vegetative parts, seeds, pollen grains, and trichomes. Macro- and micro-morphological characters, including seed and pollen shape, size, coat sculpture, trichome structure, were studied. It reveals the presence of seven species, including two endemic species. The pollen grains were zonocolpate, hexacolpate, prolate to subprolate. Three types of exine ornamentation were recognized. Also, two trichome types could be distinguished and classified into glandular and non-glandular. The glandular trichomes could be distinguished as peltate, capitate and digitiform. The eglandular trichomes were single, uniseriate, multicellular. Pollen and trichome characters were found to be valuable, while seed characters presented only minor taxonomic value. On the basis of UPGMA clustering analysis four branches and clusters were distinguished. The results offer useful data for evaluating the taxonomy of Plectranthus both at subgeneric and sectional levels. Our results indicated some degree of similarity among the species of subgenus Burnatastrum. Plectranthus arabicus is considered as a separate group and may be treated as separate subgenus. Furthermore, the endemic species Plectranthus asirensis and Plectranthus hijazensis constitute a monophyletic group and there are close relationships between this group and Plectranthus tenuiflorus. A key for the identification of the investigated taxa based on studied characters is provided.

OsSPL10 controls trichome development by interacting with OsWOX3B at both transcription and protein levels in rice(Oryza sativa L.)

Plant trichomes are a specialized cellular tissue that functions in resistance to biotic and abiotic stresses.In rice,three transcription-factor genes:OsWOX3B,HL6,and OsSPL10,have been found to control trichome development.Although studies have shown interactions between the three genes,their full relationship in trichome development is unclear.We found that the expression levels of OsWOX3B and HL6 were both reduced in OsSPL10-knockout plants but increased in OsSPL10-overexpression plants,suggesting that OsSPL10 positively regulates their expression.Physical interaction between OsSPL10 and OsWOX3B was found both in vivo and in vitro and attenuated their abilities to bind to the promoter of HL6 to activate its transcription.This mechanism may regulate trichome length by adjusting the expression of HL6.A rice gene network regulating trichome development is proposed.

Silicon Deposition in Leaf Trichomes of Cucurbitaceae Horticultural Plants: A Short Report

Silicon deposition in leaf trichome of six horticultural Cucurbitaceae species, cucumber (Cucumis sativus), pumpkin (Cucurbita maxima), melon (Cucumis melo), watermelon (Citrullus lanatus), sponge gourd (Luffa cylindrica) and bottle gourd (Lagenaria siceraria var. hispida) was observed by an X-ray microanalyzer coupled with an environmental scanning electron microscope. The elements that presented in the surface of three or four leaves of the individual species were detected and mapped by the X-ray microanalyzer. In leaves of cucumber, pumpkin, and melon, high accumulation of silicon was detected in cells surrounding the bases of the trichome hair and the hair itself deposited calcium. On the other hand, in sponge gourd and bottle gourd, high accumulation of silicon was detected only in the hair. In watermelon leaves, silicon deposited both in the hair and in cells surrounding the bases of the hair. Thus, horticultural Cucurbitaceae plants have interspecific variation in the pattern of silicon deposition in leaf trichomes.

Interspecific Variation of Micromorphology of Glandular Trichomes between two Salvia Species in South Albania

Micromorphology of glandular hairs on the leaves of Salvia officinalis L. and Salvia triloba L. was investigated by light microscopy. We noticed similiarity and variation between the two species regarding morphology of glandular trichomes. Two main types of glandular trichomes were identified on both species： peltate and capitate. Peltate trichomes consisted of a basal cell, one stalk cell and a large multisecretory head in S. officinalis L. In S. triloba L. peltate trichomes posses a basal cell, a short unicellular stalk, and a large secretory head with 8 secretory cells. In Salvia officinalis L., four types of capitate trichomes have been distinguished. Five types of capitate trichomes have been found in Salvia triloba L. The fifth type of capitate trichome, called digitiform trichome was found in S. triloba L. This determined interspecific diversity between the two Salvia species.

Less hairy leaf 1,an RNaseH-like protein,regulates trichome formation in rice through auxin

The trichomes of rice leaves are formed by the differentiation and development of epidermal cells.Plant trichomes play an important role in stress resistance and protection against direct ultraviolet irradiation.However,the development of rice trichomes remains poorly understood.In this study,we conducted ethylmethane sulfonate(EMS)-mediated mutagenesis on the wild-type(WT)indica rice‘Xida 1B’.Phenotypic analysis led to the screening of a mutant that is defective in trichome development,designated lhl1(less hairy leaf 1).We performed map-based cloning and localized the mutated gene to the 70-kb interval between the molecular markers V-9 and V-10 on chromosome 2.The locus LOC_Os02g25230 was identified as the candidate gene by sequencing.We constructed RNA interference(LHL1-RNAi)and overexpression lines(LHL1-OE)to verity the candidate gene.The leaves of the LHL1-RNAi lines showed the same trichome developmental defects as the lhl1 mutant,whereas the trichome morphology on the leaf surface of the LHL1-OE lines was similar to that of the WT,although the number of trichomes was significantly higher.Quantitative real-time PCR(RT-qPCR)analysis revealed that the expression levels of auxin-related genes and positive regulators of trichome development in the lhl1 mutant were down-regulated compared with the WT.Hormone response analysis revealed that LHL1 expression was affected by auxin.The results indicate that the influence of LHL1 on trichome development in rice leaves may be associated with an auxin pathway.

宽叶山蒿叶和艾叶的微形态鉴别

[目的]对宽叶山蒿叶和艾叶进行研究,为其鉴别提供微形态资料。[方法]利用数码相机、光学显微镜和扫描电子显微镜对其叶脉、叶表面和粉末特征进行研究。[结果](1)强光背景下,只有宽叶山蒿叶各级叶脉能清晰观察到。(2)腺毛只分布于宽叶山蒿叶的下表面,而艾叶上、下表面均有大量腺毛。(3)和艾叶相似,宽叶山蒿叶下表面也密被T形非腺毛,顶细胞有2种:一种顶细胞呈长梭形而弯曲,平均长度约1450μm(Ⅰ型);另一种顶细胞细长,扁平且扭曲,平均长度约2800μm(Ⅱ型)。(4)宽叶山蒿叶肉组织中草酸钙簇晶较少,且最大只有10μm。[结论]宽叶山蒿和艾的叶脉微形态特点及其叶上表面腺毛的有无特征可用于两者叶的快速鉴别。

植物腺毛分泌物研究进展

植物腺毛(Plant glandular trichomes,GTs)是具有分泌能力的植物表皮毛,分布在茎、叶、花器官甚至果实的表面,可产生具有抗生物胁迫和非生物胁迫能力的腺毛分泌物(Glandular trichomes secretions),被誉为“生物合成工厂”。植物腺毛分泌物属于次生代谢产物,在医疗保健、植物源农药及食品工业等行业具有重要的应用价值。本文主要综述了植物腺毛结构、腺毛分泌物种类、提取分离及其功能活性等方面的研究进展,并对存在的问题和应用前景进行了分析与展望,以期为植物腺毛分泌物在医药、农业及食品领域的开发与利用提供参考。

NtMYB17过表达对烟草腺毛发育的影响

作为植物预防生物和非生物胁迫的第一道防线,以及次生代谢物的分泌和合成场所,烟草腺毛的分子调控研究对烟草抵抗逆境胁迫和品质育种具有重要意义。为明确烟草MYB转录因子NtMYB17在调控腺毛发育过程中的生物学功能,在普通烟草中克隆了NtMYB17基因,并对其保守结构域和基因结构进行分析,利用qRT-PCR技术分析了NtMYB17的表达模式,进一步结合亚细胞定位试验和过表达试验验证了基因的功能。结果表明:NtMYB17基因全长939 bp,共编码312个氨基酸,具有典型的MYB结构域,亚细胞定位于细胞核中;qRT-PCR结果显示,NtMYB17在腺毛中的表达量是去腺毛叶片中表达量的8倍,且在花蕾和幼叶中的表达量较高,在根中的表达量最低;在过表达NtMYB17基因的烟草植株中分枝型腺毛数量增加。该研究表明NtMYB17基因对烟草腺毛的形态发育具有调控作用。

中国杨属叶表皮毛状体微形态特征

为讨论叶表皮毛状体特征的分类学价值和系统学意义,借助体视显微镜和扫描电镜对中国杨属(Populus)33个物种的叶表皮毛状体进行了观察和分析。结果表明:杨属物种叶片毛状体整体上是非腺状的、简单的、基底固定的;除胡杨(P.euphratica)叶表皮没有毛状体外,其余物种叶表皮均被有毛状体,但毛状体的分布、形态、长度等在物种间存在不同程度差异。毛状体外形(圆柱状至条带状)、弯曲程度(直立至曲卷)、相对于叶表皮表面的方向(伏贴或不伏贴)及毛状体长度具有一定的分类学意义。结合分子系统发育研究提供的进化框架,本研究认为杨属叶表皮毛状体特征在亚属水平难以区分,但胡杨亚属(subg.Turanga)和白杨亚属(subg.Populus)在种间水平可区分很多物种,尤其是白杨亚属内的物种毛状体差异大;脂杨亚属(subg.Tacamahaca)内叶片毛状体相似且稳定,但不同分支上的叶片毛状体在长度上有差异。毛状体特征整合后可划分为以下类型:无毛、毡毛、绢毛、短柔毛和长柔毛。

烟草NtJAZ15基因对腺毛发生的影响

为验证NtJAZ15对烟草腺毛发生的影响,探究NtJAZ15调控腺毛发生的分子机制,本研究从K326中克隆了NtJAZ15基因,并对其进行了生物信息学和组织表达模式分析,通过创制NtJAZ15敲除和过表达突变体,分析其对腺毛发生的调控作用。结果表明,NtJAZ15-1和NtJAZ15-2在不同烟草品种中高度保守,具有典型的TIFY和Jas结构域,属于JAZ家族。NtJAZ15在各组织中均表达,且各组织中NtJAZ15-2表达量均高于NtJAZ15-1。NtJAZ15基因敲除突变体烟叶长柄和短柄腺毛密度增加,过表达突变体则相反。qRT-PCR结果表明NtJAZ15可显著影响NtWo、NtCycB2、NtHD9、NtHD12的表达,但对NtMIXTA的表达影响不显著。因此,NtJAZ15负调控烟草长柄和短柄腺毛发生,NtWo、NtCycB2、NtHD9、NtHD12可能参与NtJAZ15调控烟草腺毛发生。

杂交种“豫烟11”赖百当二萜含量和腺毛密度的定向改良

【背景和目的】豫烟11是由8306与MSK326杂交而来的烤烟品种,因其父本8306腺毛分泌物中含有赖百当二萜而具有晾晒烟的香气特征。为彰显豫烟11的烤烟特色香气风格,对其腺毛分泌物的含量和组成进行定向改良。【方法】利用8306-1(NtCPS2敲除的8306)与MSK326杂交获得豫烟11-1,利用8306-2(NtCPS2、NtCycB2共同敲除的8306)与HK326(NtCycB2敲除的K326)杂交获得豫烟11-2,对其农艺性状、腺毛形态和腺毛分泌物进行测定,并对相关基因序列及表达水平进行分析。【结果】(1)分子检测表明,豫烟11-1、豫烟11-2中的NtCPS2均为突变型;豫烟11-1中的NtCycB2为野生型,而豫烟11-2中的则为突变型。(2)田间试验表明,豫烟11-1、豫烟11-2生长发育正常,农艺性状与豫烟11基本一致;豫烟11-1腺毛密度与豫烟11相比无显著差异,豫烟11-2腺毛密度比豫烟11提高了40.6%;豫烟11-1、豫烟11-2腺毛分泌物中均不含有赖百当二萜,豫烟11-1腺毛分泌物含量与豫烟11相比无显著变化,豫烟11-2腺毛分泌物含量比豫烟11提高了70.2%。(3)qRT-PCR分析表明,豫烟11-1中二萜合成相关基因NtCPS2、NtABS、NtCBTS、NtCYP71D16的表达量与豫烟11相比无显著差异,但在豫烟11-2中则显著提高,而二萜合成上游基因NtGPPS、NtGGPPS的表达量在3个株系间无显著变化。【结论】本研究利用NtCPS2和NtCycB2基因突变,实现了豫烟11腺毛密度、腺毛分泌物组分和含量的定向改良,为针对上述性状的分子育种提供了范例。

NtJAZ9基因参与调控烟草腺毛发生的功能研究

【目的】探究茉莉酮酸调控烟草腺毛发生的分子机制。【方法】对茉莉酮酸信号关键抑制子NtJAZ9进行同源克隆、生物信息学分析和基因功能研究。【结果】(1)NtJAZ9有两条同源序列NtJAZ9-1和NtJAZ9-2,编码区长度分别为1008 bp和996 bp。(2)亚细胞定位结果表明NtJAZ9蛋白定位在细胞核中。在各组织中NtJAZ9-1相对表达量均高于NtJAZ9-2,NtJAZ9-1在茎表皮中表达量最高,NtJAZ9-2在叶中表达量最高。(3)NtJAZ9过表达植株叶面腺毛密度降低,NtJAZ9基因敲除植株腺毛密度显著增加,保护毛密度差异不显著。茉莉酮酸甲酯(methyl jasmonate,MeJA)可显著促进长柄腺毛的发生,喷施后过表达株系长柄腺毛密度增加1.76倍,敲除株系长柄腺毛增加0.36倍。【结论】NtJAZ9基因参与调控烟草腺毛的发生,并在一定程度上影响了MeJA信号对烟草腺毛发生的调控作用。

Profiles of the Headspace Volatile Organic and Essential Oil Compounds from the Tunisian Cardaria draba (L.) Desv. and Its Leaf and Stem Epidermal Micromorphology

In this work, we investigated aroma volatiles emanated by dry roots, stems, leaves, flowers, and fruits of Cardariadraba (L.) Desv. growing wild in Tunisia and its aerial part essential oils (EOs) composition. A total of 37 volatileorganic compounds (96.7%–98.9%) were identified;4 esters, 4 alcohols, 7 hydrocarbons, 12 aldehydes, 5 ketones,1 lactone, 1 organosulfur compound, 2 organonitrogen compounds, and 1 acid. The hydrocarbons form the maingroup, representing 49.5%–84.6% of the total detected volatiles. The main constituent was 2,2,4,6,6-pentamethylheptane(44.5%–76.2%) reaching the highest relative percentages. Forty-two compounds were determined in thetwo fractions of EOs, representing 98.8% and 97.2% of the total oil composition, respectively. The principal componentswere hexadecanoic acid (34.6%), 6-methyl-5-hepten-2-one (18.3%), decanal (15.0%), 6,10,14-trimethyl-2-pentadecanone (13.2%), and n-pentacosane (13%). Micromorphological details of the leaf and stem epidermisusing light microscopy revealed polygonal cells with sinuous walls in the adaxial and abaxial leaf surfaces andnearly rectangular and long ones with linear and thick walls for the stem epidermis. The stomata complexes wereanisocytic in the leaf epidermis and mainly anisocytic and rarely paracytic in the stem epidermis. Non-glandulartrichomes were unbranched and long with an acute apex or short with a convex apex. The glandular ones wereidentified for the first time in this species. They were short-stalked with a large secretory head. The highest stomatalindex (17.02%) was recorded in the abaxial leaf surface. The identification of headspace volatiles and essentialoil compounds can be used to characterize this species, and the various epidermis micromorphologicalfeatures are very useful for biosystematics taxonomic studies within Brassicaceae.

The Effects of Climate,Soil and Cultivar on the Content of Surface Trichome Exudates from Fresh Flue-cured Leaves

[Objective] The aim was to study the effect of climate and soil on the content of surface trichome exudates from fresh flue-cured leaves. [Method] The experiment was conducted in 2009 in Longgang, Weining and Tianzhu of Guizhou Province with flue-cured tobacco variety Yun 85. Mature tobacco leaves were taken from lower, middle and upper plant positions respectively and major cuticular com-ponents of the leaves were extracted with methylene chloride and their chemical compositions were analyzed with GC-MS. [Result] The result showed that there was large difference among trichome exudates of leaves grown under different climatic conditions. The leaf trichome exudates from Tianzhu were quite higher than those from Weining and Longgang, and trichome exudates difference between Tianzhu and Longgang was significant. Soil conditions had considerable effect on the content of tobacco leaf surface trichome exudates, leaf from Longgang soil had highest con-tent, fol owed by Tianzhu soil leaf, Weining soil leaf had lowest content. Under vari-ous climatic conditions, the contents of leaf trichome exudates of same soil were in-consistent, indicating the presence of certain climate and soil factor interaction; The contents of leaf trichome exudates from four cultivars in Longgang showed large difference, Nanjiang 3 was the lowest, fol owed by K326, Guiyan 201 was high, and Yunyan85 the highest. The content of leaf trichome exudates of Yunyan85 was more than two times of that of Nanjiang 3. [Conclusion] The Effect of climate factor on the content of leaf trichome exudates was greater than that of cultivar, which was then larger than soil condition.

荒漠植物表皮毛的凝结水形成及吸收机制研究进展

荒漠植物适应长期缺水条件形成了从空气吸水并在体表滞留及向体内运输的高度进化的结构特征,其叶片表面附属结构如表皮毛等在收集、储存及运输凝结水方面具有重要的生物学意义。本文基于目前相关研究进展,简要概述了凝结水对荒漠植物的生物学效应及生态效应,阐述了叶片表面润湿性与其集水能力相关理论,基于此重点阐述荒漠植物叶表特殊结构(表皮毛)在凝结水形成、运输、吸收过程中的重要作用,并总结了植物体表滞留及吸收凝结水的相关研究方法,为深入理解基于表皮毛结构特征驱动的荒漠植物收集凝结水的策略以及干旱荒漠植物的抗逆机制提供理论依据。