Wall-bound Phenolics Research Articles

Different patterns of the photosynthetic apparatus recovery during early rehydration following drought stress in two types of intergeneric hybrid of triticale

The study aimed to reveal the activity of the photosynthetic apparatus during early rehydration in double haploid (DH) lines of triticale with different types of flag leaf rolling in response to soil drought. Two DH lines, showing full (Type O) and limited (Type V) flag leaf rolling, were investigated. The measurements of chlorophyll fluorescence, analysis of red/far-red fluorescence excitation spectra, as well as detection of selected PSII proteins (PsbA/D1, PsbS) and transmembrane cytochrome complex b6f (PetC/Rieske protein) were performed. The measurements were carried out on the last day of drought and after 1 h, 3 h, and 5 h of rehydration. The physiological condition of flag leaves was studied based on measurements of water relations, the progress of leaf senescence, histochemical detection of reactive oxygen species, and the content of sugars and phenolic compounds. In Type O, as compared with Type V, a further decline in the activity of the photosynthetic apparatus was observed during the post-drought rehydration period. This was accompanied by the accumulation of reactive oxygen species and more advanced senescence of flag leaves. Fluorescence excitation spectra revealed disorders in photosynthetic light conversion in Type O flag leaves during drought and rehydration over the entire range of excitation wavelengths corresponding to UVC, UVB, and UVA radiation. Type V flag leaves developed an effective UV protection mechanism in the form of increased accumulation of cell wall-bound phenolics, which efficiently absorbed UV radiation. Both types differed in the level of accumulation of PsbA, PsbS, and PetC proteins during drought and early rehydration. Soil drought caused a similar reduction in grain yield in both types. However, in Type O, the largest share in the grain yield was ascribed to the ears of lateral stems, while in Type V to the ears of the main stems. Our research has shown that the limited rolling of flag leaves under drought stress corresponds to the effective photoprotection of the photosynthetic apparatus in the first hours of rehydration.

Toward resilient agriculture and environmental protection: The role of cell wall-bound phenolics

Due to their unpredicted scope, duration, and effects, soil droughts pose a serious threat to agriculture. Gradual steppe formation and desertification of farming and horticultural lands are the consequences of climate change. Irrigation systems for field crops do not offer the most viable solution, as they depend heavily on freshwater resources, which are currently scarce. For these reasons, it is necessary to obtain crop cultivars that are not only more tolerant to soil drought, but also capable of effective use of water during and after drought. In this article, we highlight the importance of cell wall-bound phenolics in the efficient adaptation of crops to arid environments and protection of soil water resources.

Tolerance to Zn toxicity in the halophyte Lepidium latifolium L. and the effect of salt on Zn tolerance and accumulation

Halophytes exhibit a high cross-tolerance to multiple stresses that enable them to survive under harsh environmental conditions. We hypothesized that salt treatment in halophytes improves their tolerance against other stressors. To investigate the salt-mediated heavy metal tolerance in halophytes, Lepidium latifolium (Brassicaceae) was cultivated in the absence or presence of salt (100 mM NaCl) and excess Zn (200 μM ZnSO4), alone or in combination, for four weeks in the hydroponic medium. Salt treatment ameliorated the reduction of photosynthetic pigments in Zn-stressed plants and decreased Zn accumulation in the young leaves. The activity of peroxidase increased by both Zn toxicity and salt treatments; its maximum activity was achieved under the combination of both treatments associated with a significant reduction in malondialdehyde concentration. The activity of polyphenol oxidase increased by Zn stress alone or in combination with salt, accompanied by accumulation of free and cell wall-bound phenolics and enhanced lignin deposition in the leaves. Our results showed a mitigating effect of salt treatment in Zn-stressed plants through the activation of antioxidant defense and accumulation of phenolic compounds including flavonoids. Our results suggest L. latifolium as suitable species for revegetation and rehabilitation of saline soils contaminated with heavy metals.

Diverse responses of halophyte and glycophyte Lepidium species to the salt-mediated amelioration of nickel toxicity and accumulation.

Tolerance mechanisms employed by plants under environmental stresses can protect them against other co-occurring stresses. In this study, the effect of pre-exposure and simultaneous salt treatment on nickel (Ni) toxicity tolerance in one halophyte (L. sativum) and one glycophyte (L. latifolium) Lepidium species in hydroponics was investigated. In order to compare the species independent from their salt and Ni tolerance level, the glycophyte was subjected to lower salt and Ni concentrations and for a shorter period of time than the halophyte. Salt (NaCl) was applied at 50 and 100mM concentrations and Ni was provided at an equal free Ni2+ activity by adding 100 and 200µM Ni as single stresses, but 130 and 300µM Ni for the treatment of its combination with salt in the glycophyte and halophyte, respectively. Temporal analyses of signaling molecules revealed that the halophyte is characteristically different from the glycophyte in that it exhibits a higher constitutive level of nitric oxide and hydrogen peroxide, a longer duration of response to Ni, and its augmentation by salt. In addition to higher biomass and less Ni accumulation in salt-treated plants, the concentrations of free thiol groups, leaf pigments, proline, free and cell wall-bound phenolics contents, and the activity of phenolic metabolizing enzymes were higher in L. latifolium under the combined salt and Ni treatments than under the single Ni stress. In contrast, the biomass and most biochemical parameters of Ni-stressed L. sativum plants were not enhanced by salt treatment but rather decreased. Our findings shed light on cross-tolerance mechanisms in halophytes and uncovered halophyte survival strategies under multiple stresses.

Modulation of phenylpropanoid and lignin biosynthetic pathway is crucial for conferring resistance in pigeon pea against Fusarium wilt

To elucidate the role of the phenylpropanoid pathway in the expression of resistance during compatible and incompatible interactions between pigeon pea and wilt-causing vascular pathogen Fusarium udum, we estimated the total phenol content, lignin, phenolic acids and activity of enzymes involved in lignin polymerization of monolignols and examined the expression pattern of lignin biosynthesis genes. Our results demonstrated a higher accumulation of free and cell wall-bound phenolics and total lignin content in the highly resistant pigeon pea genotype ICP 14623 as compared to susceptible genotype ICP 14166. An increased activity of phenylpropanoid pathway-associated defense enzymes such as Phenylalanine ammonia-lyase, polyphenol oxidase, ascorbate and guaiacol- dependent peroxidases in resistant pigeon pea genotypes suggests their role in resistance. Moreover, analysis of lignin biosynthesis genes revealed their differential expression during resistant and susceptible interactions, revealed their crucial role in imparting resistance against wilt. Overall, our results indicated the role of physical and biochemical components of the phenylpropanoid pathway in the expression of resistance in pigeon pea against Fusarium wilt.

Non-rolling flag leaves use an effective mechanism to reduce water loss and light-induced damage under drought stress.

The study reports on four different types of flag leaf rolling under soil drought in relation to the level of cell wall-bound phenolics. The flag leaf colonization by aphids, as a possible bioindicator of the accumulation of cell wall-bound phenolics, was also estimated. The proteins of the photosynthetic apparatus that form its core and are crucial for maintaining its stability (D1/PsbA protein), limit destructive effects of light (PsbS, a protein binding carotenoids in the antennas) and participate in efficient electron transport between photosystems II (PSII) and PSI (Rieske iron-sulfur protein of the cytochrome b6f complex) were evaluated in two types of flag leaf rolling. Additionally, biochemical and physiological reactions to drought stress in rolling and non-rolling flag leaves were compared. The study identified four types of genome-related types of flag leaf rolling. The biochemical basis for these differences was a different number of phenolic molecules incorporated into polycarbohydrate structures of the cell wall. In an extreme case of non-rolling dehydrated flag leaves, they were found to accumulate high amounts of cell wall-bound phenolics that limited cell water loss and protected the photosynthetic apparatus against excessive light. PSII was also additionally protected against excess light by the accumulation of photosynthetic apparatus proteins that ensured stable and efficient transport of excitation energy beyond PSII and its dissipation as far-red fluorescence and heat. Our analysis revealed a new type of flag leaf rolling brought about by an interaction between wheat and rye genomes, and resulting in biochemical specialization of flexible, rolling and rigid, non-rolling parts of the flag leaf. The study confirmed limited aphid colonization of the flag leaves with enhanced content of cell wall-bound phenolics. Non-rolling leaves developed effective adaptation mechanisms to reduce both water loss and photoinhibitory damage to the photosynthetic apparatus under drought stress.

A robust method of extraction and GC-MS analysis of Monophenols exhibited UV-B mediated accumulation in Arabidopsis.

The online version contains supplementary material available at 10.1007/s12298-022-01150-2.

Activity of the photosynthetic apparatus in dehydrated leaves of a perennial shrub Rosa rubiginosa L. with different levels of drought memory

The aim of the study was to analyze the activity of the photosynthetic apparatus during induced dehydration of leaves harvested from perennial shrubs of Rosa rubiginosa growing at wet and dry sites and differing in the level of drought memory. The markers of drought memory included accumulation of D1 (PsbA) protein, chaperone Cpn60, Rubisco activase (RA), and Rubisco larger subunit (RbcL). The study investigated the levels of soluble carbohydrates and phenolic compounds, of cell wall-bound phenolics, non-enzymatic antioxidants, and assimilation pigments.During induced dehydration, leaves from the dry site exhibited slower water loss and greater activity of the photosynthetic apparatus, particularly in terms of effectiveness of electron transport between PSII and PSI. They also effectively dissipated excessive excitation energy in the form of heat and far-red fluorescence. Higher level of D1 protein in the leaves collected from the dry site was accompanied by lower accumulation of Cpn60, RA and RbcL proteins and considerably higher content of soluble carbohydrates and carotenoids.Drought memory in R. rubiginosa may be associated with a low level of proteins responsible for photosynthetic fixation of CO2 and reduced content of chlorophyll a and b, and also with enhanced accumulation of D1 protein and soluble carbohydrates and carotenoids.

Interactions between zinc and Phomopsis longicolla infection in roots of Glycine max.

Phomopsis. longicolla is a hemibiotrophic fungus causing significant soybean yield loss worldwide. To reveal the role of zinc in plant-pathogen interactions, soybean seedlings were grown hydroponically with a range of Zn concentrations, 0.06 µM (deficient, Zn0), 0.4 µM (optimal growth), 1.5 µM, 4 µM, 12 µM, and toxic 38 μM, and were subsequently inoculated with P. longicolla via the roots. In vivo analysis of metal distribution in tissues by micro-X-ray fluorescence showed local Zn mobilization in the root maturation zone in all treatments. Decreased root and pod biomass, and photosynthetic performance in infected plants treated with 0.4 µM Zn were accompanied with accumulation of Zn, jasmonoyl-L-isoleucine (JA-Ile), jasmonic acid, and cell wall-bound syringic acid (cwSyA) in roots. Zn concentration in roots of infected plants treated with 1.5 µM Zn was seven-fold higher than in the 0.4 µM Zn treatment, which together with accumulation of JA-Ile, cwSyA, cell wall-bound vanilic acid and leaf jasmonates contributed to maintaining photosynthesis and pod biomass. Host-pathogen nutrient competition and phenolics accumulation limited the infection in Zn-deficient plants. The low infection rate in Zn 4 µM-treated roots correlated with salicylic and 4-hydroxybenzoic acid, and cell wall-bound p-coumaric acid accumulation. Zn toxicity promoted pathogen invasion and depleted cell wall-bound phenolics. The results show that manipulation of Zn availability improves soybean resistance to P. longicolla by stimulating phenolics biosynthesis and stress-inducible phytohormones.

Targeted profiling reveals metabolic perturbations in cryptogein-cotransformed hairy root cultures of Nicotiana tabacum

Although β-cryptogein gene expression was known to induce growth and phenolic metabolites accumulation in tobacco, however, the consequence on specialized metabolites other than phenolic has been scantly studied, and no report on the changes in primary metabolites is available. Tobacco (Nicotiana tabacum) hairy root cultures expressing β-cryptogein under CaMV 35S promoter were described here. GC–MS and HPLC–DAD based analyses of volatile and non-volatile metabolites including phenolic were carried out to study the variations in the levels of metabolites (both primary and specialized) in transgenic lines as compared to controls. Wall-bound phenolics and three forms of soluble phenolics (free, glycosyl-bound and ester-bound soluble phenolics) as well as chlorogenic acid contents were compared between cryptogein-cotransformed and control lines. In support of metabolite changes, semiquantitative expression analyses of selected genes of phenylpropanoid and terpenoid pathways viz. phenylalanine ammonia lyase (PAL), 4-coumaryl CoA ligase (4CL), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and 1-deoxy-d-xylulose-5-phosphate synthase (DXS), were performed. Furthermore, activities of important enzymes (PAL and 4CL) involved in phenylpropanoid pathway were analyzed. Increase of phenolic compounds, fatty acid-derivatives, alkaloids (nicotine and nornicotine), benzenoids, sugars (sucrose, fructose, galactose and lactose) and a few metabolites originated from glycolysis pathway intermediates were noticed in Ri-crypt-transformed hairy roots (RCTHR) with decline in the contents of terpenoids and many amino acids (except proline). Increased gene expressions of PAL and 4CL along with enhanced activities of respective enzymes in RCTHR were supported the phenolics accumulation. Reduced expressions of HMGR and DXS genes were observed which supported the reduced amount of terpenoid metabolites. This study suggests a possible channelling of carbon pool towards phenylpropanoid/benzenoid pathway as well as lipoxygenase pathway and nicotine biosynthesis in tobacco hairy roots expressing a β-cryptogein gene.

Cell wall composition and thickness affect mesophyll conductance to CO2 diffusion in Helianthus annuus under water deprivation.

Water deprivation affects photosynthesis, leaf anatomy, and cell wall composition. Although the former effects have been widely studied, little is known regarding those changes in cell wall major (cellulose, hemicelluloses, pectin, and lignin) and minor (cell wall-bound phenolics) compounds in plants acclimated to short- and long-term water deprivation and during recovery. In particular, how these cell wall changes impact anatomy and/or photosynthesis, specifically mesophyll conductance to CO2 diffusion (gm), has been scarcely studied. To induce changes in photosynthesis, cell wall composition and anatomy, Helianthus annuus plants were studied under five conditions: (i) control (i.e. without stress) (CL); (ii) long-term water deficit stress (LT); (iii) long-term water deficit stress with recovery (LT-Rec); (iv) short-term water deficit stress (ST); and (v) short-term water deficit stress with recovery (ST-Rec), resulting in a wide photosynthetic range (from 3.80 ± 1.05 μmol CO2 m-2 s-1 to 24.53 ± 0.42 μmol CO2 m-2 s-1). Short- and long-term water deprivation and recovery induced distinctive responses of the examined traits, evidencing a cell wall dynamic turnover during plants acclimation to each condition. In particular, we demonstrated for the first time how gm correlated negatively with lignin and cell wall-bound phenolics and how the (cellulose+hemicelloses)/pectin ratio was linked to cell wall thickness (Tcw) variations.

OPDA and ABA accumulation in Pb-stressed Zygophyllum fabago can be primed by salicylic acid and coincides with organ-specific differences in accumulation of phenolics

Salicylic acid (SA) is a well-known priming agent that is widely used to protect plants against stressing agents, including heavy metals as Pb. A better understanding of the mechanisms that enable plants to counteract Pb toxicity would help to select strategies for land reclamation programs. Here we used a metallicolous population of Zygophyllum fabago to assess the extent to which SA pretreatment modulates Pb-induced changes in phenol metabolism and stress-related phytohormone levels in roots and leaves. Our data revealed that accumulation of different phytohormones, lignin, soluble and wall-bound phenolics as well as peroxidase (PRX) activity in Pb-stressed plants differed after SA-pretreatment. Exposure to Pb led to the induction of soluble and cell wall-bound PRX activities, particularly those involved in the oxidation of coniferyl alcohol and ferulic acid, while pretreatment with SA reduced the Pb-induced stimulation of PRX activities in roots but increased them in leaves. SA-treatment by itself induced accumulation of ABA and the JA-precursor 12-oxo-phytodienoic acid (OPDA) in the roots. Pb in turn inhibited these SA-induced effects with the exception of OPDA accumulation that was primed by the pretreatment. The SA treatment also induced accumulation of OPDA in leaves but suppressed the accumulation of JA-Ile although with relatively small absolute changes. Notably, Pb-induced accumulation of ABA was primed in the leaves of SA-pretreated plants. Together our data suggest that priming of OPDA accumulation in the roots and of ABA in the leaves by SA-pretreatment may play important regulatory roles, possibly via regulating PRX activities, for Pb stress in plants.

UPLC-DAD-QToF/MS analysis of green tea phenolic metabolites in their free, esterified, glycosylated, and cell wall-bound forms by ultra-sonication, agitation, and conventional extraction techniques

In this study, phenolic metabolites in their free, soluble esterified, and soluble glycosylated forms in green tea infusions and cell wall-bound forms in solid residues obtained by ultrasound treatment, agitation treatment, and normal infusion preparation method were investigated. In total, thirty-three phenolic compounds were characterized including twenty-two flavonoids and eleven phenolic acids using UPLC-DAD-QToF/MS analysis. The flavonoids were sub-characterized as flavanols and flavonols, and phenolic acids were sub-characterized as hydroxybenzoic acid, hydroxybenzoylquinic acid, hydroxycinnamic acid, and hydroxycinnamoylquinic acid. As flavanols, EGCG was dominant in their free form and was significantly higher (p < 0.05) in ultrasound (4094 mg/100 g) and agitation (3906 mg/100 g) treatment than normal infusion (1657 mg/100 g). Kaempferol was predominant flavonols in their free form and was significantly higher (p < 0.05) in ultrasound (54.78 mg/100 g) and agitation (53.87 mg/100 g) treatment than normal infusion (30.67 mg/100 g). In contrary, cell wall-bound phenolics were dominated by gallic acid and were significantly higher (p < 0.05) in normal solid residues (2582 mg/100 g) than agitation (527 mg/100 g) and ultrasound (157 mg/100 g) treatment. This study provides a useful database of different forms of phenolic metabolite profiling of aqueous green tea infusions and solid residues.

Biochemical responses of soil-borne necrotroph Sclerotium rolfsii during the pathogenesis on chickpea

Southern blight caused by Sclerotium rolfsii is a fast spreading and destructive disease of chickpea yield. This disease cause severe damage to plant on almost all growth stage. In our study we have selected two genotype of chickpea i.e one is resistant genotype (GNG1958) and another susceptible genotype (L550) and two isolates of S. rolfsii i.e., highly aggressive (C4) and least aggressive (L9). Both isolates were inoculated on both genotypes and observation of enzymatic activity was done. Peroxidase activity was highest in case of susceptible genotype inoculated with least aggressive isolate. There was depletion in catalase and ascorbate peroxidase activity and enhancement in activity of peroxidase whether it was inoculated with highly or least aggressive isolate, but there was variation in superoxide dismutase activity. The enhanced biochemical activities during plant pathogen interaction triggers the defense related enzymes such as wall-bound phenolics, flavonoids and induction of hypersensitive reaction (HR) etc., which resulted in cell strengthening and enhances resistance to pathogen. The depletion of catalase and ascorbate peroxidase during host-parasite interaction might be due to induction of antioxidant enzyme in plant which leads to oxidative stress and multiplication of pathogen. In case of superoxide dismutase activity when resistant genotype inoculated with least aggressive isolate there was increase in activity but when susceptible genotype inoculated with least aggressive isolate there was decline in superoxide dismutase activity. Which shows superoxide dismutase activity could improve superoxide scavenging system of cells and favor accumulation of superoxide which mainly contributes in damaging the concentration and damage to cell membrane.

Lignin plays a key role in determining biomass recalcitrance in forage grasses

Lignocellulosic biomass is an abundant renewable feedstock, rich in polysaccharides that are covalently linked with lignin. In this study, biomass composition of nine forage grasses revealed the role of lignin in biomass recalcitrance. We determined the profiles of cell wall-bound phenolics, lignin, monosaccharides, enzymatic saccharification, and the chemical fingerprints using Fourier transform infrared (FTIR) and Raman spectroscopies. Coastcross and Tifton 85, both bermuda grass cultivars, showed lower lignin content and higher saccharification at 2 h and 72 h of enzymatic hydrolysis, supporting their use as valuable sources of carbohydrates for ethanol production. Principal component analysis (PCA) of thirteen different cell wall traits revealed that lignin was a hierarchical factor in reduced saccharification of forage grasses. As such, lignin content could be used as a marker for the selection of grass cultivars for genetic engineering programs for improved sustainable biofuel production.

Phellem Cell-Wall Components Are Discriminants of Cork Quality in Quercus suber.

Cork is a renewable, non-wood high valued forest product, with relevant ecological and economic impact in the Mediterranean-type ecosystems. Currently, cork is ranked according to its commercial quality. The most valuable planks are chosen for cork stoppers production. Cork planks with adequate thickness and porosity are classified as stoppable quality cork (SQC). The chemical composition of cork is known, but the regulation of metabolic pathways responsible of cork production and composition, hence of cork quality, is largely unknown. Here, we tested the hypothesis that post-genomic events may be responsible for the development of SQC and N-SQC (non-stoppable quality cork). Here, we show that combined proteomics and targeted metabolomics (namely soluble and cell wall bound phenolics) analyzed on recently formed phellem allows discriminate cork planks of different quality. Phellem cells of SQC and N-SQC displayed different reducing capacity, with consequential impact on both enzymatic pathways (e.g., glycolysis) and other cellular functions, including cell wall assembly and suberization. Glycolysis and respiration related proteins were abundant in both cork quality groups, whereas the level of several proteins associated to mitochondrial metabolism was higher in N-SQC. The soluble and cell wall-bound phenolics in recently formed phellem clearly discriminated SQC from N-SCQ. In our study, SQC was characterized by a high incorporation of aromatic components of the phenylpropanoid pathway in the cell wall, together with a lower content of hydrolysable tannins. Here, we propose that the level of hydrolysable tannins may represent a valuable diagnostic tool for screening recently formed phellem, and used as a proxy for the quality grade of cork plank produced by each tree.

Beyond the wall: High-throughput quantification of plant soluble and cell-wall bound phenolics by liquid chromatography tandem mass spectrometry

Plants accumulate several thousand of phenolic compounds, including lignins and flavonoids, which are mainly synthesized through the phenylpropanoid pathway, and play important roles in plant growth and adaptation. A novel high-throughput ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) method was established to quantify the levels of 19 flavonoids and 15 other phenolic compounds, including acids, aldehydes, and alcohols. The chromatographic separation was performed in 10 min, allowing for the resolution of isomers such as 3-, 4-, and 5-chlorogenic acids, 4-hydroxybenzoic and salicylic acids, isoorientin and orientin, and luteolin and kaempferol. The linearity range for each compound was found to be in the low fmol to the high pmol. Furthermore, this UHPLC-MS/MS approach was shown to be very sensitive with limits of detection between 1.5 amol to 300 fmol, and limits of quantification between 5 amol to 1000 fmol. Extracts from maize seedlings were used to assess the robustness of the method in terms of recovery efficiency, matrix effect, and accuracy. The biological matrix did not suppress the signal for 32 out of the 34 metabolites under investigation. Additionally, the majority of the analytes were recovered from the biological samples with an efficiency above 75%. All flavonoids and other phenolic compounds had an intra- and inter-day accuracy within a ±20% range, except for coniferyl alcohol and vanillic acid. Finally, the quantification of flavonoids, free and cell wall-bound phenolics in seedlings from two maize lines with contrasting phenolic content was successfully achieved using this methodology.

Control of Fusarium wilt in wheat seedlings by grain priming with defensin-like protein

The exogenous application of natural plant resistance inducer is a new interesting way for disease management. From this point of view, this study investigated the effect of wheat grain priming with defensin on the resistance of the grown plants against the Fusarium wilt. The results showed that priming enhanced the antioxidant system represented in antioxidant enzymes (superoxide dismutase, polyphenol oxidase, soluble and cell wall-bound peroxidase) and non-enzymatic antioxidant compounds (proline, free soluble and cell wall-bound phenols) in the plants. This results in decreasing the H2O2 content and lipid peroxidation in these plants, which protects plants from the oxidative stress. Defensin priming not only improved the antioxidant system but also improved the hydrolysis processes. Under infection, the protease activity in the primed plants decreased compared to its highly significant increase in the non-primed group. Defensin priming also increased the activity of the phosphatases and amylase which increased the soluble phosphate and sugar. This served the high metabolic activity of the defensin-primed plants. The highly significant decrease in the shikimic acid content in the defensin-primed group ensured its high metabolic activity. All these changes are initiated by the regulation of defense signal molecules such as jasmonic and abscisic acids. This helped the plants grown from defensin-primed grains to overcome the Fusarium infection.

Silicon influences growth and mycorrhizal responsiveness in strawberry plants.

Effect of silicon (Si) on the response of strawberry (Fragaria × ananassa var. Parus) plants to arbuscular mycorrhizal fungus (AMF) was studied under growth chamber conditions. Plants were grown in perlite irrigated with nutrient solution without (- Si) or with (+ Si) 3mmolL-1 Si (~ 84mg L-1 Si as Na2SiO3) in the absence (- AMF) or presence (+ AMF) of fungus. Dry matter production, root colonization rate, photosynthesis rate and water relation parameters were all improved by both Si and AMF, and the highest amounts were achieved by + Si + AMF treatment. Mycorrhizal effectiveness increased by Si treatment associated with higher Si concentration in the + AMF plants. Leaf concentrations of total soluble and cell wall-bound phenolics were increased by Si accompanied by the enhanced activity of phenylalanine ammonia lyase, but not polyphenol oxidase. Profile of phenolics compound revealed that gallic acid, caffeic acid, epicatechin, chlorogenic acid, ellagic acid and kaempferol increased by both Si and AMF treatments, while p-coumaric acid decreased. In addition to vegetative growth, both treatments improved fruit yield and its quality parameters. Our results showed that Si and AMF acted in a synergistic manner and improved growth and biochemical parameters in strawberry plants. However, the mechanism for Si-mediated increase of mycorrhizal effectiveness is not known, thereby needing further elucidation.

Cloning and Functional Characterization of Two 4-Coumarate: CoA Ligase Genes from Selaginella moellendorffii.

Selaginella is an extant lycopodiophyte genus, which is representative of an ancient lineage of tracheophytes. The important evolutionary status makes it a valuable resource for the study of metabolic evolution in vascular plants. 4-coumarate: CoA ligase (4CL) is the pivotal enzyme that controls the flow of carbon through the phenylpropanoid metabolic pathway into the specific lignin, flavonoid, and wall-bound phenolics biosynthesis pathways. Although 4CLs have been extensively characterized in other vascular plants, little is known of their functions in Selaginella. Here, we isolated two 4CL genes (Sm4CL1 and Sm4CL2) from Selaginella moellendorffii. Based on the enzymatic activities of the recombinant proteins, both of these genes encoded bona fide 4CLs. The 4CL isoforms in S. moellendorffii have different activities: Sm4CL2 was more active than Sm4CL1. The enzymatic properties and gene expression patterns indicated that the 4CL genes have been conserved in the evolution of vascular plants.