Plant Vascular Architecture Determines the Pattern of Herbivore-Induced Systemic Responses in Arabidopsis thaliana

The induction of systemic responses in plants is associated with the connectivity between damaged and undamaged leaves, as determined by vascular architecture. Despite the widespread appreciation for studying variation in induced plant defense, few studies have characterized spatial variability of induction in the model species, Arabidopsis thaliana. Here we show that plant architecture generates fine scale spatial variation in the systemic induction of invertase and phenolic compounds. We examined whether the arrangement of leaves along the stem (phyllotaxy) produces predictable spatial patterns of cell-wall bound and soluble invertase activities, and downstream phenolic accumulation following feeding by the dietary specialist herbivore, Pieris rapae and the generalist, Spodoptera exigua. Responses were measured in leaves within and outside of the damaged orthostichy (leaves sharing direct vascular connections), and compared to those from plants where source-sink transport was disrupted by source leaf removal and by an insertional mutation in a sucrose transporter gene (suc2-1). Following herbivore damage to a single, middle-aged leaf, induction of cell-wall and soluble invertase was most pronounced in young and old leaves within the damaged orthostichy. The pattern of accumulation of phenolics was also predicted by these vascular connections and was, in part, dependent on the presence of source leaves and intact sucrose transporter function. Induction also occurred in leaves outside of the damaged orthostichy, suggesting that mechanisms may exist to overcome vascular constraints in this system. Our results demonstrate that systemic responses vary widely according to orthostichy, are often herbivore-specific, and partially rely on transport between source and sink leaves. We also provide evidence that patterns of induction are more integrated in A. thaliana than previously described. This work highlights the importance of plant vascular architecture in determining patterns of systemic induction, which is likely to be ecologically important to insect herbivores and plant pathogens.     

Effect of cadmium on the phenolic compounds formation in the callus cultures derived from various organs of the tea plant

The effects of cadmium (6.3 × 10^?5 M or 10.6 × 10^?5 M) on the growth of tea plant (Camellia sinensis L.) callus cultures derived from leaves, stems, and roots and on the formation, in these cultures, of phenolic compounds, including flavans and lignin, which are characteristic of the tea plant, were investigated. In the calli derived from leaves and stems, cadmium treatment decreased the biomass increment, while in the calli derived from roots, growth characteristics remained at the control level. Under the effect of cadmium, the content of phenolic compounds, including flavans, in the leaf calli decreased, while in the stem and root calli, it either increased (at the cadmium concentration of 6.3 × 10^?5 M), or was close to a control one (at the cadmium concentration of 10.6 × 10^?5 M). The lignin content in the root and stem calli increased, but it did not change in the leaf calli. All this data demonstrate that the cadmium-induced changes in phenolic metabolism of the tea plant callus culture depended both on the cadmium concentration in the medium and on the origin of calli.     

Metabolomic Analysis and Phenylpropanoid Biosynthesis in Hairy Root Culture of Tartary Buckwheat Cultivars

Buckwheat, Fagopyrum tataricum Gaertn., is an important medicinal plant, which contains several phenolic compounds, including one of the highest content of rutin, a phenolic compound with anti-inflammatory properties. An experiment was conducted to investigate the level of expression of various genes in the phenylpropanoid biosynthetic pathway to analyze in vitro production of anthocyanin and phenolic compounds from hairy root cultures derived from 2 cultivars of tartary buckwheat (Hokkai T8 and T10). A total of 47 metabolites were identified by gas chromatography–time-of-flight mass spectrometry (GC-TOFMS) and subjected to principal component analysis (PCA) in order to fully distinguish between Hokkai T8 and T10 hairy roots. The expression levels of phenylpropanoid biosynthetic pathway genes, through qRT-PCR, showed higher expression for almost all the genes in T10 than T8 hairy root except for FtF3’H-2 and FtFLS-2. Rutin, quercetin, gallic acid, caffeic acid, ferulic acid, 4-hydroxybenzoic acid, and 2 anthocyanin compounds were identified in Hokkai T8 and T10 hairy roots. The concentration of rutin and anthocyanin in Hokkai T10 hairy roots of tartary buckwheat was several-fold higher compared with that obtained from Hokkai T8 hairy root. This study provides useful information on the molecular and physiological dynamic processes that are correlated with phenylpropanoid biosynthetic gene expression and phenolic compound content in F. tataricum species.     

一氧化氮参与盐胁迫下长春花酚类代谢的调控研究

为研究外源一氧化氮(NO)调控盐胁迫下长春花中酚类化合物的响应,采用液相色谱—质谱联用(LCMS)技术靶向分析梯度浓度硝普纳(SNP)处理对盐胁迫下长春花幼苗根、茎、花、叶4个部位中酚类化合物组分及含量水平的变化。结果共鉴定出L-苯丙氨酸和18种酚类物质,C6C1类5种、C6C3类5种、C6C3C6类8种,其中原儿茶酸、绿原酸、槲皮素在长春花根、茎、花、叶4个部位中均存在;不同浓度SNP处理后长春花不同部位酚类化合物响应积累明显不同,其中C6C1和C6C3小分子酚酸类化合物主要积累在根和茎中,C3C6C3类主要富集在花和叶中;L-苯丙氨酸在茎、叶中相对含量较高,盐胁迫下茎中含量显著升高,且随外源NO浓度增大呈下降趋势。外源NO影响盐胁迫下植物器官中酚类化合物的积累和变化,其中根和茎响应敏感,从种类和相对含量的角度,茎和叶更适合检测酚类化合物。     

A survey of mangiferin and hydroxycinnamic acid ester accumulation in coffee (Coffea) leaves: biological implications and uses

Background and Aims

The phenolic composition of Coffea leaves has barely been studied, and therefore this study conducts the first detailed survey, focusing on mangiferin and hydroxycinnamic acid esters (HCEs).

Methods

Using HPLC, including a new technique allowing quantification of feruloylquinic acid together with mangiferin, and histochemical methods, mangiferin content and tissue localization were compared in leaves and fruits of C. pseudozanguebariae, C. arabica and C. canephora. The HCE and mangiferin content of leaves was evaluated for 23 species native to Africa or Madagascar. Using various statistical methods, data were assessed in relation to distribution, ecology, phylogeny and use.

Key Results

Seven of the 23 species accumulated mangiferin in their leaves. Mangiferin leaf-accumulating species also contain mangiferin in the fruits, but only in the outer (sporophytic) parts. In both leaves and fruit, mangiferin accumulation decreases with ageing. A relationship between mangiferin accumulation and UV levels is posited, owing to localization with photosynthetic tissues, and systematic distribution in high altitude clades and species with high altitude representatives. Analyses of mangiferin and HCE content showed that there are significant differences between species, and that samples can be grouped into species, with few exceptions. These data also provide independent support for various Coffea lineages, as proposed by molecular phylogenetic analyses. Sampling of the hybrids C. arabica and C. heterocalyx cf. indicates that mangiferin and HCE accumulation may be under independent parental influence.

Conclusions

This survey of the phenolic composition in Coffea leaves shows that mangiferin and HCE accumulation corresponds to lineage recognition and species delimitation, respectively. Knowledge of the spectrum of phenolic accumulation within species and populations could be of considerable significance for adaptation to specific environments. The potential health benefits of coffee-leaf tea, and beverages and masticatory products made from the fleshy parts of Coffea fruits, are supported by our phenolic quantification.Key words: Arabica coffee, C. arabica, C. canephora, chlorogenic acids, Crop Wild Relatives (CWRs), coffee-leaf tea, hybridization, hydroxycinnamic acids, mangiferin, phenolic compounds, phylogeny, robusta coffee     

Effects of Kaolin (M-99-099) Application on Antioxidant and Phenolic Compounds in Tea Leaves (<Emphasis Type="Italic">Camellia sinensis</Emphasis> L.O. Kuntze)

In this study, the effects of kaolin (M-99-099) applications on the total phenolic and antioxidant contents of tea leaves (Camellia sinensis (L.) O. Kuntze) harvested in three different periods were investigated. For this purpose, four different strategies including standard fertilizer application (T), 3% kaolin+standard fertilizer application (Ka₁), 6% kaolin+standard fertilizer application (Ka₂), and control (C) (nothing applied) were used to compare the effects of these strategies on total phenolic content, FRAP values, and DPPH radical scavenging capacities of tea leaves. It has been proven that the kaolin applications, Ka₁ and Ka₂, increase the phenolic content and antioxidant contents of tea samples. While the kaolin applications have higher values at 1st harvest than those of T and C, they have the lowest values at 3rd harvest.     

Effects of catechins on Agrobacterium-mediated genetic transformation of Camellia sinensis

In this study, recalcitrance of tea plant ( Camellia sinensis) to Agrobacterium-mediated genetic transformation was investigated with an emphasis on specialized compounds in tea. Chemical constituents in tea leaves and calli were extracted into liquid Luria–Bertani (LB) medium to determine their biological activities on Agrobacterium growth, virulence, and plant transformation efficiency. Compared to the control Agrobacterium grown in LB medium, tea leaf extract containing 6.5 mg mL^?1 catechins resulted in an 84.6 % reduction of Agrobacterium growth, a 73–36 % suppression of expression for the six virulence (vir) genes, browning of infected tobacco explant wounds, and an absence of transient or stable transformation events. Tea callus extract, containing 0.22 mg mL^?1 catechins, did not significantly affect Agrobacterium growth or tobacco transgenic hairy root generation, whereas it enhanced the expression of some vir genes. Treatment with authentic catechin mixtures (other than caffeine) dissolved in LB resulted in suppression of Agrobacterium growth, vir gene expression, and tobacco transformation efficiency. Our data suggest that catechins are the key active constituents in tea leaves. Transient transformation efficiencies of tea leaves were much lower than those of tobacco leaves as indicated by the GUS (β-glucuronidase) assay, probably a result of inhibition by the catechins present in tea leaves. Lower transformation efficiencies of tea calli suggested that additional plant factor(s) might also exert inhibitory effects on tea plant transformation. Agrobacterium rhizogenes ATCC 15834 induced transgenic roots from the tea explants with 15–20 % efficiency. Our data suggested catechins inhibition of tea gene transformation could be overcome by using optimized strains of Agrobacterium.     

Bioconversion of tea polyphenols to bioactive theabrownins by Aspergillus fumigatus

Theabrownins (TB) are water-soluble phenolic compounds associated with the various health benefits of Pu-erh tea, a post-fermented Chinese dark tea. This work reports on the production of theabrownins from infusions of sun-dried green tea leaves using a pure culture of Aspergillus fumigatus isolated from a solid-state Pu-erh tea fermentation. A theabrownins yield of 158 g kg^?1 sun-dried green tea leaves was obtained in 6 days at 45 °C in an aerobic fermentation. In a 2 l fermenter, the yield of theabrownins was 151 g kg^?1 sun-dried green tea leaves in 48 h of aerobic culture (45 °C, 1 vvm aeration rate, 250 rpm agitation speed). Extracellular polyphenol oxidase and peroxidase of A. fumigatus contributed to this bioconversion. Repeated batch fermentation process was used for producing theabrownins but was less productive than the batch process.     

DNA repair in higher plants; photoreactivation is the major DNA repair pathway in non-proliferating cells while excision repair (nucleotide excision repair and base excision repair) is active in proliferating cells

We investigated expression patterns of DNA repair genes such as the CPD photolyase, UV-DDB1, CSB, PCNA, RPA32 and FEN-1 genes by northern hybridization analysis and in situ hybridization using a higher plant, rice (Oryza sativa L. cv. Nipponbare). We found that all the genes tested were expressed in tissues rich in proliferating cells, but only CPD photolyase was expressed in non-proliferating tissue such as the mature leaves and elongation zone of root. The removal of DNA damage, cyclobutane pyrimidine dimers and (6–4) photoproducts, in both mature leaves and the root apical meristem (RAM) was observed after UV irradiation under light. In the dark, DNA damage in mature leaves was not repaired efficiently, but that in the RAM was removed rapidly. Using a rice 22K custom oligo DNA microarray, we compared global gene expression patterns in the shoot apical meristem (SAM) and mature leaves. Most of the excision repair genes were more strongly expressed in SAM. These results suggested that photoreactivation is the major DNA repair pathway for the major UV-induced damage in non-proliferating cells, while both photoreactivation and excision repair are active in proliferating cells.     

Salicylhydroxamic acid (SHAM) negatively mediates tea herbivore-induced direct and indirect defense against the tea geometrid Ectropis obliqua

We investigated the effect of the SHAM treatment of tea plants on their induced defense on a tea geometrid (TG), Ectropis obliqua Prout. Treatment of tea leaves with SHAM reduced the performance of TG and TG-elicited level of the lipoxygenase gene CsiLOX1 and the putative allene oxide synthase gene CsiAOS1. The release of wound-induced green leaf volatiles (GLVs) and the expression of the hydroperoxide lyase (HPL) gene CsiHPL1 were also reduced by SHAM treatment. The negative effect of SHAM dramatically reduced the total hebivore-induced plant volatiles (HIPVs) and the attractiveness to the parasitoid wasp Apanteles sp. These results indicated that SHAM may negatively mediate tea defense response against TG by modulating the wound-induced emission of GLVs, the expression of genes involved in oxylipin pathway, and the emission of other HIPV compounds that mediate direct and indirect defenses.     

Root Exudation of Phytochemicals in Arabidopsis Follows Specific Patterns That Are Developmentally Programmed and Correlate with Soil Microbial Functions

Plant roots constantly secrete compounds into the soil to interact with neighboring organisms presumably to gain certain functional advantages at different stages of development. Accordingly, it has been hypothesized that the phytochemical composition present in the root exudates changes over the course of the lifespan of a plant. Here, root exudates of in vitro grown Arabidopsis plants were collected at different developmental stages and analyzed using GC-MS. Principle component analysis revealed that the composition of root exudates varied at each developmental stage. Cumulative secretion levels of sugars and sugar alcohols were higher in early time points and decreased through development. In contrast, the cumulative secretion levels of amino acids and phenolics increased over time. The expression in roots of genes involved in biosynthesis and transportation of compounds represented in the root exudates were consistent with patterns of root exudation. Correlation analyses were performed of the in vitro root exudation patterns with the functional capacity of the rhizosphere microbiome to metabolize these compounds at different developmental stages of Arabidopsis grown in natural soils. Pyrosequencing of rhizosphere mRNA revealed strong correlations (p<0.05) between microbial functional genes involved in the metabolism of carbohydrates, amino acids and secondary metabolites with the corresponding compounds released by the roots at particular stages of plant development. In summary, our results suggest that the root exudation process of phytochemicals follows a developmental pattern that is genetically programmed.     

Concomitant Induction of Systemic Resistance to Pseudomonas syringae pv. lachrymans in Cucumber by Trichoderma asperellum (T-203) and Accumulation of Phytoalexins

Most studies on the reduction of disease incidence in soil treated with Trichoderma asperellum have focused on microbial interactions rather than on plant responses. This study presents conclusive evidence for the induction of a systemic response against angular leaf spot of cucumber (Pseudomonas syringae pv. lachrymans) following application of T. asperellum to the root system. To ascertain that T. asperellum was the only microorganism present in the root milieu, plants were grown in an aseptic hydroponic growth system. Disease symptoms were reduced by as much as 80%, corresponding to a reduction of 2 orders of magnitude in bacterial cell densities in leaves of plants pretreated with T. asperellum. As revealed by electron microscopy, bacterial cell proliferation in these plants was halted. The protection afforded by the biocontrol agent was associated with the accumulation of mRNA of two defense genes: the phenylpropanoid pathway gene encoding phenylalanine ammonia lyase (PAL) and the lipoxygenase pathway gene encoding hydroxyperoxide lyase (HPL). This was further supported by the accumulation of secondary metabolites of a phenolic nature that showed an increase of up to sixfold in inhibition capacity of bacterial growth in vitro. The bulk of the antimicrobial activity was found in the acid-hydrolyzed extract containing the phenolics in their aglycone form. High-performance liquid chromatography analysis of phenolic compounds showed a marked change in their profile in the challenged, preelicited plants relative to that in challenged controls. The results suggest that similar to beneficial rhizobacteria, T. asperellum may activate separate metabolic pathways in cucumber that are involved in plant signaling and biosynthesis, eventually leading to the systemic accumulation of phytoalexins.