Will the climate of plant origins influence the chemical profiles of cuticular waxes on leaves of Leymus chinensis in a common garden experiment?

Cuticular wax covering the leaf surface plays important roles in protecting plants from biotic and abiotic stresses. Understanding the way in which plant leaf cuticles reflect their growing environment could give an insight into plant resilience to future climate change. Here, we analyzed the variations of cuticular waxes among 59 populations of Leymus chinensis in a common garden experiment, aiming to verify how environmental conditions influence the chemical profiles of cuticular waxes. In total, eight cuticular wax classes were identified, including fatty acids, aldehydes, primary alcohols, alkanes, secondary alcohols, ketones, β‐diketones, and alkylresorcinols, with β‐diketones the predominant compounds in all populations (averaged 67.36% across all populations). Great intraspecific trait variations (ITV) were observed for total wax coverage, wax compositions, and the relative abundance of homologues within each wax class. Cluster analysis based on wax characteristics could separate 59 populations into different clades. However, the populations could not be separated according to their original longitudes, latitudes, annual temperature, or annual precipitation. Redundancy analysis showed that latitude, arid index, and the precipitation from June to August were the most important parameters contributing to the variations of the amount of total wax coverage and wax composition and the relative abundance of wax classes. Pearson's correlation analysis further indicated that the relative abundance of wax classes, homologues in each wax class, and even isomers of certain compound differed in their responses to environmental factors. These results suggested that wax deposition patterns of L. chinensis populations formed during adaptations to their long‐term growing environments could inherit in their progenies and exhibit such inheritance even these progenies were exported to new environments.     

Developmental Changes in Composition and Morphology of Cuticular Waxes on Leaves and Spikes of Glossy and Glaucous Wheat (Triticum aestivum L.)

The glossy varieties (A14 and Jing 2001) and glaucous varieties (Fanmai 5 and Shanken 99) of wheat (Triticum aestivum L.) were selected for evaluation of developmental changes in the composition and morphology of cuticular waxes on leaves and spikes. The results provide us with two different wax development patterns between leaf and spike. The general accumulation trend of the total wax load on leaf and spike surfaces is first to increase and then decrease during the development growth period, but these changes were caused by different compound classes between leaf and spike. Developmental changes of leaf waxes were mainly the result of variations in composition of alcohols and alkanes. In addition, diketones were the third important contributor to the leaf wax changes in the glaucous varieties. Alkanes and diketones were the two major compound classes that caused the developmental changes of spike waxes. For leaf waxes, β- and OH-β-diketones were first detected in flag leaves from 200-day-old plants, and the amounts of β- and OH-β-diketones were significantly higher in glaucous varieties compared with glossy varieties. In spike waxes, β-diketone existed in all varieties, but OH-β-diketone was detectable only in the glaucous varieties. Unexpectedly, the glaucous variety Fanmai 5 yielded large amounts of OH-β-diketone. There was a significant shift in the chain length distribution of alkanes between early stage leaf and flag leaf. Unlike C₂₈ alcohol being the dominant chain length in leaf waxes, the dominant alcohol chain length of spikes was C₂₄ or C₂₆ depending on varieties. Epicuticular wax crystals on wheat leaf and glume were comprised of platelets and tubules, and the crystal morphology changed constantly throughout plant growth, especially the abaxial leaf crystals. Moreover, our results suggested that platelets and tubules on glume surfaces could be formed rapidly within a few days.     

小麦品系CP98(11)不同器官表皮蜡质组分和蜡质晶体结构的差异分析

为明确小麦不同器官表皮蜡质晶体结构和蜡质组分的差异,该研究以小麦品系CP98(11)为材料,在小麦扬花期分别取小麦的旗叶、叶鞘、穗下茎、花药和颖壳,利用气相色谱技术对各器官表皮蜡质组分进行鉴定,并通过扫描电镜观察其蜡质晶体结构。结果表明:(1)小麦不同器官的蜡质成分共鉴定出30种,主要为初级醇、二酮、烷烃、脂肪醛、脂肪酸、酯。(2)叶鞘、穗下茎、颖壳的蜡质中二酮含量最高,分别占蜡质总量的78.96%、67.03%和68.6%;花药的蜡质中烷烃含量最高(75.82%);旗叶的蜡质中初级醇含量最高(45.91%),其次为烷烃33.19%。(3)扫描电镜观察显示,旗叶正面的蜡质晶体呈片状结构,旗叶反面和颖壳的蜡质晶体结构呈片状与柱状混合的结构,花药的蜡质呈明显的波浪状结构,穗下茎和叶鞘的蜡质晶体呈柱状结构。     

Geographically Related Variation in Epicuticular Wax Traits of Pinus nigra Populations from Southern Carpathians and Central Balkans – Taxonomic Considerations

The chemical composition of epicuticular waxes of nine populations from three Pinus nigra J. F. Arnold subspecies (namely subsp. nigra, subsp. banatica (Borbás ) Novák , and subsp. pallasiana (Lamb .) Holmboe ) from Southern Carpathians and central Balkan Peninsula were analyzed using GC/MS and GC/FID chromatography, and multivariate statistical techniques with respect to biogeography and taxonomy. In the needle waxes, four primary alcohols and 14 n‐alkanes ranging from C₂₁ to C₃₃ were identified, and the most abundant compounds were the four odd‐numbered n‐alkanes C₂₇, C₂₅, C₂₃, and C_29. Multivariate statistical analyses (CDA and CA) have shown existence of three P. nigra groups and suggested clinal differentiation as a mechanism of genetic variation across a geographic area: the first group consisted of the southernmost populations of subsp. pallasiana from Macedonia, the second consisted of the northernmost subsp. banatica populations from Romania, while all populations in Serbia described as three different subspecies (nigra, banatica, and pallasiana) formed the third group together with subsp. nigra population from Bosnia and Herzegovina. According to simple linear regression, geographic latitude and four bioclimatic parameters were moderately correlated with the contents of epicuticular wax compounds that are important in population discrimination, while stepwise multiple regression showed that latitude participated in most of the regression models for predicting the composition of the epicuticular waxes. These results agree with CDA and CA analysis, and confirmed the possibility of recognition of fine geographic differentiation of the analyzed P. nigra populations.     

Identification of In-Chain-Functionalized Compounds and Methyl-Branched Alkanes in Cuticular Waxes of Triticum aestivum cv. Bethlehem

In this work, cuticular waxes from flag leaf blades and peduncles of Triticum aestivum cv. Bethlehem were investigated in search for novel wax compounds. Seven wax compound classes were detected that had previously not been reported, and their structures were elucidated using gas chromatography-mass spectrometry of various derivatives. Six of the classes were identified as series of homologs differing by two methylene units, while the seventh was a homologous series with homologs with single methylene unit differences. In the waxes of flag leaf blades, secondary alcohols (predominantly C₂₇ and C₃₃), primary/secondary diols (predominantly C₂₈) and esters of primary/secondary diols (predominantly C₅₀, combining C₂₈ diol with C₂₂ acid) were found, all sharing similar secondary hydroxyl group positions at and around C-12 or ω-12. 7- and 8-hydroxy-2-alkanol esters (predominantly C₃₅), 7- and 8-oxo-2-alkanol esters (predominantly C₃₅), and 4-alkylbutan-4-olides (predominantly C₂₈) were found both in flag leaf and peduncle wax mixtures. Finally, a series of even- and odd-numbered alkane homologs was identified in both leaf and peduncle waxes, with an internal methyl branch preferentially on C-11 and C-13 of homologs with even total carbon number and on C-12 of odd-numbered homologs. Biosynthetic pathways are suggested for all compounds, based on common structural features and matching chain length profiles with other wheat wax compound classes.     

Cuticle lipids on heteromorphic leaves of Populus euphratica Oliv. growing in riparian habitats differing in available soil moisture

Populus euphratica is an important native tree found in arid regions from North Africa and South Europe to China, and is known to tolerate many forms of environmental stress, including drought. We describe cuticle waxes, cutin and cuticle permeability for the heteromorphic leaves of P. euphratica growing in two riparian habitats that differ in available soil moisture. Scanning electron microscopy revealed variation in epicuticular wax crystallization associated with leaf type and site. P. euphratica leaves are dominated by cuticular wax alkanes, primary‐alcohols and fatty acids. The major cutin monomers were 10,16‐diOH C_16:0 acids. Broad‐ovate leaves (associated with adult phase growth) produced 1.3‐ and 1.6‐fold more waxes, and 2.1‐ and 0.9‐fold more cutin monomers, than lanceolate leaves (associated with juvenile phase growth) at the wetter site and drier site, respectively. The alkane‐synthesis‐associated ECERIFERUM1 (CER1), as well as ABC transporter‐ and elongase‐associated genes, were expressed at much higher levels at the drier than wetter sites, indicating their potential function in elevating leaf cuticle lipids in the dry site conditions. Higher cuticle lipid amounts were closely associated with lower cuticle permeability (both chlorophyll efflux and water loss). Our results implicate cuticle lipids as among the xeromorphic traits associated with P. euphratica adult‐phase broad‐ovate leaves. Results here provide useful information for protecting natural populations of P. euphratica and their associated ecosystems, and shed new light on the functional interaction of cuticle and leaf heterophylly in adaptation to more arid, limited‐moisture environments.     

A dual role for integrin‐linked kinase and β1‐integrin in modulating cardiac aging

Cardiac performance decreases with age, which is a major risk factor for cardiovascular disease and mortality in the aging human population, but the molecular mechanisms underlying cardiac aging are still poorly understood. Investigating the role of integrin‐linked kinase (ilk) and β1‐integrin (myospheroid, mys) in Drosophila, which colocalize near cardiomyocyte contacts and Z‐bands, we find that reduced ilk or mys function prevents the typical changes of cardiac aging seen in wildtype, such as arrhythmias. In particular, the characteristic increase in cardiac arrhythmias with age is prevented in ilk and mys heterozygous flies with nearly identical genetic background, and they live longer, in line with previous findings in Caenorhabditis elegans for ilk and in Drosophila for mys. Consistent with these findings, we observed elevated β1‐integrin protein levels in old compared with young wild‐type flies, and cardiac‐specific overexpression of mys in young flies causes aging‐like heart dysfunction. Moreover, moderate cardiac‐specific knockdown of integrin‐linked kinase (ILK)/integrin pathway‐associated genes also prevented the decline in cardiac performance with age. In contrast, strong cardiac knockdown of ilk or ILK‐associated genes can severely compromise cardiac integrity, including cardiomyocyte adhesion and overall heart function. These data suggest that ilk/mys function is necessary for establishing and maintaining normal heart structure and function, and appropriate fine‐tuning of this pathway can retard the age‐dependent decline in cardiac performance and extend lifespan. Thus, ILK/integrin‐associated signaling emerges as an important and conserved genetic mechanism in longevity, and as a new means to improve age‐dependent cardiac performance, in addition to its vital role in maintaining cardiac integrity.     

Chemotaxonomic Considerations of the n‐Alkane Composition in Pinus heldreichii,P. nigra,and P. peuce

The n‐alkane composition in the leaf cuticular waxes of natural populations of Bosnian pine (Pinus heldreichii), Austrian pine (P. nigra), and Macedonian pine (P. peuce) was compared for the first time. The range of n‐alkanes was wider in P. nigra (C₁₆ – C₃₃) than in P. heldreichii and P. peuce (C₁₈ – C₃₃). Species also diverged in abundance and range of dominant n‐alkanes (P. heldreichii: C₂₃, C₂₇, and C₂₅; P. nigra: C₂₅, C₂₇, C₂₉, and C₂₃; P. peuce: C₂₉, C₂₅, C₂₇, and C₂₃). Multivariate statistical analyses (PCA, DA, and CA) generally pointed out separation of populations of P. nigra from populations of P. heldreichii and P. peuce (which were, to a greater or lesser extent, separated too). However, position of these species on the basis of n‐alkane composition was in accordance neither with infrageneric classification nor with recent molecular and terpene investigations.     

植物角质层蜡质的化学组成研究综述

角质层是植物与外界的第一接触面,而角质层蜡质则是由位于角质层外的外层蜡质和深嵌在角质层中的内层蜡质两部分构成。植物角质层蜡质成分极其复杂,具有重要的生理功能。综述了有关植物角质层蜡质的化学组成信息,探讨了目前植物角质层蜡质化学成分研究中存在的一些问题,展望了角质层蜡质成分的研究前景。     

γ‐glutamyl transpeptidase 1 specifically suppresses green‐light avoidance via GABAA receptors in Drosophila

Drosophila larvae innately show light avoidance behavior. Compared with robust blue‐light avoidance, larvae exhibit relatively weaker green‐light responses. In our previous screening for genes involved in larval light avoidance, compared with control w¹¹¹⁸ larvae, larvae with γ‐glutamyl transpeptidase 1 (Ggt‐1) knockdown or Ggt‐1 mutation were found to exhibit higher percentage of green‐light avoidance which was mediated by Rhodopsin6 (Rh6) photoreceptors. However, their responses to blue light did not change significantly. By adjusting the expression level of Ggt‐1 in different tissues, we found that Ggt‐1 in malpighian tubules was both necessary and sufficient for green‐light avoidance. Our results showed that glutamate levels were lower in Ggt‐1 null mutants compared with controls. Feeding Ggt‐1 null mutants glutamate can normalize green‐light avoidance, indicating that high glutamate concentrations suppressed larval green‐light avoidance. However, rather than directly, glutamate affected green‐light avoidance indirectly through GABA, the level of which was also lower in Ggt‐1 mutants compared with controls. Mutants in glutamate decarboxylase 1, which encodes GABA synthase, and knockdown lines of the GABA_A receptor, both exhibit elevated levels of green‐light avoidance. Thus, our results elucidate the neurobiological mechanisms mediating green‐light avoidance, which was inhibited in wild‐type larvae.

     

Effect of Conidiobolus coronatus on the Cuticular and Internal Lipid Composition of Tettigonia viridissima Males

Conidiobolus coronatus is an entomopathogenic fungus which has a potential as a biological control agent of insects. The cuticular and internal lipid composition of infected and noninfected Tettigonia viridissima males were analyzed by GC/MS. A total of 49 compounds were identified in the infected and noninfected males, including fatty acids, fatty acid methyl esters (FAMEs), n‐alkanes, alcohols, sterols, and other organic compounds. The most abundant components of the cuticular and internal lipids of the insects were fatty acids. After exposure to C. coronatus, the cuticular lipids of the T. viridissima males contained 17 free fatty acids from C(8) to C(22), while the cuticular lipids of the noninfected insects contained only 15 fatty acids from C(12) to C(24). The cuticular and internal lipids of both the infected and the noninfected males also contained five FAMEs from C(15) to C(19), seven n‐alkanes from C(25) to C(34), five alcohols from C(16) to C(25), five sterols, and the following six other organic compounds: azelaic acid, phenylacetic acid, glutaric acid, benzoic acid, sebacic acid, and glycerol. The compounds which were present only in the cuticular lipids of the infected males could be due to fungal infection.     

Ontogenetic variation in chemical and physical characteristics of adaxial apple leaf surfaces

The reaction of plants to environmental factors often varies with developmental stage. It was hypothesized, that also the cuticle, the outer surface layer of plants is modified during ontogenesis. Apple plantlets, cv. Golden Delicious, were grown under controlled conditions avoiding biotic and abiotic stress factors. The cuticular wax surface of adaxial apple leaves was analyzed for its chemical composition as well as for its micromorphology and hydrophobicity just after unfolding of leaves ending in the seventh leaf insertion. The outer surface of apple leaves was formed by a thin amorphous layer of epicuticular waxes. Epidermal cells of young leaves exhibited a distinctive curvature of the periclinal cell walls resulting in an undulated surface of the cuticle including pronounced lamellae, with the highest density at the centre of cells. As epidermal cells expanded during ontogenesis, the upper surface showed only minor surface sculpturing and a decrease in lamellae. With increasing leaf age the hydrophobicity of adaxial leaf side decreased significantly indicated by a decrease in contact angle. Extracted from plants, the amount of apolar cuticular wax per area unit ranged from only 0.9 microgcm(-2) for the oldest studied leaf to 1.5 microgcm(-2) for the youngest studied leaf. Differences in the total amount of cuticular waxes per leaf were not significant for older leaves. For young leaves, triterpenes (ursolic acid and oleanolic acid), esters and alcohols were the main wax components. During ontogenesis, the proportion of triterpenes in total mass of apolar waxes decreased from 32% (leaf 1) to 13% (leaf 7); absolute amounts decreased by more than 50%. The proportion of wax alcohols and esters, and alkanes to a lesser degree, increased with leaf age, whereas the proportion of acids decreased. The epicuticular wax layer also contained alpha-tocopherol described for the first time to be present also in the epicuticular wax. The modifications in the chemical composition of cuticular waxes are discussed in relation to the varying physical characteristics of the cuticle during ontogenesis of apple leaves.     

Leaf cuticular waxes are arranged in chemically and mechanically distinct layers: evidence from Prunus laurocerasus L.

The composition and spatial arrangement of cuticular waxes on the leaves of Prunus laurocerasus were investigated. In the wax mixture, the triterpenoids ursolic acid and oleanolic acid as well as alkanes, fatty acids, aldehydes, primary alcohols and alcohol acetates were identified. The surface extraction of upper and lower leaf surfaces yielded 280 mg m ^{? 2} and 830 mg m ^{? 2}, respectively. Protocols for the mechanical removal of waxes from the outermost layers of the cuticle were devised and evaluated. With the most selective of these methods, 130 mg m ^{? 2} of cuticular waxes could be removed from the adaxial surface before a sharp, physically resistant boundary was reached. Compounds thus obtained are interpreted as ‘epicuticular waxes’ with respect to their localization in a distinct layer on the surface of the cutin matrix. The epicuticular wax film can be transferred onto glass and visualized by scanning electron microscopy. Prunus laurocerasus epicuticular waxes consisted entirely of aliphatic compounds, whereas the remaining intracuticular waxes comprised 63% of triterpenoids. The ecological relevance of this layered structure for recognition by phytotrophic fungi and herbivorous insects that probe the surface composition for sign stimuli is discussed.