Vessel-associated cells in angiosperm xylem: Highly specialized living cells at the symplast-apoplast boundary.

BACKGROUND: Vessel-associated cells (VACs) are highly specialized, living parenchyma cells that are in direct contact with water-conducting, dead vessels. The contact may be sparse or in large tight groups of parenchyma that completely surrounds vessels. VACs differ from vessel distant parenchyma in physiology, anatomy, and function and have half-bordered pits at the vessel-parenchyma juncture. The distinct anatomy of VACs is related to the exchange of substances to and from the water-transport system, with the cells long thought to be involved in water transport in woody angiosperms, but where direct experimental evidence is lacking. SCOPE: This review focuses on our current knowledge of VACs regarding anatomy and function, including hydraulic capacitance, storage of nonstructural carbohydrates, symplastic and apoplastic interactions, defense against pathogens and frost, osmoregulation, and the novel hypothesis of surfactant production. Based on microscopy, we visually represent how VACs vary in dimensions and general appearance between species, with special attention to the protoplast, amorphous layer, and the vessel-parenchyma pit membrane. CONCLUSIONS: An understanding of the relationship between VACs and vessels is crucial to tackling questions related to how water is transported over long distances in xylem, as well as defense against pathogens. New avenues of research show how parenchyma-vessel contact is related to vessel diameter and a new hypothesis may explain how surfactants arising from VAC can allow water to travel under negative pressure. We also reinforce the message of connectivity between VAC and other cells between xylem and phloem.

Prediction of auxin response elements based on data fusion in Arabidopsis thaliana.

The plant hormone "auxin" is a key regulator of plant development and environmental responses. Many genes in Arabidopsis thaliana are known to be up-regulated in response to auxin. Auxin response factors activate or repress the expression of genes by binding at their promoter regions within auxin response elements (AuxRE) that are key regulatory cis-acting motives. Therefore, the identification of auxin-response elements is among the most important issues to understand the auxin regulation mechanisms. Thus, searching the TGTCTC motif is an unreliable method to identify AuxRE because many AuxRE variants may also be functional. In the present study, we perform an In-silico prediction of AuxREs in promoters of primary auxin responsive genes. We exploit microarray data of auxin response in Arabidopsis thaliana seedlings, in order to provide biological annotation to AuxRE. We apply a data fusion method based on the combined use of evidence theory and fuzzy sets to scan upstream sequences of response genes.

Profile comparison and valorization of Tunisian Salvia aegyptiaca and S. verbenaca aerial part extracts via hyphenated high-performance thin-layer chromatography.

Aerial parts of the rare species Salvia aegyptiaca L. and S. verbenaca L. were collected from arid habitats in southern Tunisia. Their polar (ethanol-water) and mid-polar (ethyl acetate) extracts were analyzed non-targeted via a developed high-performance thin-layer chromatography profiling hyphenated with 12 effect-directed assays and 8 different physico-chemical detections. Bioactive compound zones were observed with inhibiting activities on α-glucosidase, ß-glucosidase, ß-glucuronidase, acetylcholinesterase, butyrylcholinesterase and tyrosinase, with radical scavenging (antioxidative) effects, and with activities against Gram-negative and Gram-positive bacteria. The effect-directed profile patterns showed common bioactive zones for different collection sites of the same species and distinct differences between species. Such characteristic profiles can be used to prove authenticity. Genotoxic, estrogen-like and androgen-like compounds were not detected even at higher amounts applied (for extracts from 1.6 mg sample). In the physico-chemical profiling, further organic substances were selectively detected, which highlighted the complexity of the multi-component mixture. The Tunisian sage profiles were further compared to the frequently used S. folium L. and S. officinalis L. leaves, and to reference mixtures containing phenolic acids and tanshinones. Selected bioactive zones in the S. verbenaca extracts were characterized by high-resolution mass spectrometry, and some mass signals were attributed to a caffeic acid derivative and to oleanolic and ursolic acids. Such effect-directed non-target profiling allows straightforward comparison not only of sage but of plant extracts in general.

An Evidence Theory and Fuzzy Logic Combined Approach for the Prediction of Potential ARF-Regulated Genes in Quinoa.

Quinoa constitutes among the tolerant plants to the challenging and harmful abiotic environmental factors. Quinoa was selected as among the model crops destined for bio-saline agriculture that could contribute to the staple food security for an ever-growing worldwide population under various climate change scenarios. The auxin response factors (ARFs) constitute the main contributors in the plant adaptation to severe environmental conditions. Thus, the determination of the ARF-binding sites represents the major step that could provide promising insights helping in plant breeding programs and improving agronomic traits. Hence, determining the ARF-binding sites is a challenging task, particularly in species with large genome sizes. In this report, we present a data fusion approach based on Dempster-Shafer evidence theory and fuzzy set theory to predict the ARF-binding sites. We then performed an "In-silico" identification of the ARF-binding sites in Chenopodium quinoa. The characterization of some known pathways implicated in the auxin signaling in other higher plants confirms our prediction reliability. Furthermore, several pathways with no or little available information about their functions were identified to play important roles in the adaptation of quinoa to environmental conditions. The predictive auxin response genes associated with the detected ARF-binding sites may certainly help to explore the biological roles of some unknown genes newly identified in quinoa.

Phytosynthesis of Zinc Oxide Nanoparticles Using Ceratonia siliqua L. and Evidence of Antimicrobial Activity.

Carob (Ceratonia siliqua L.) is a tree crop cultivated extensively in the eastern Mediterranean regions but that has become naturalized in other regions as well. The present study focused on the green synthesis of zinc oxide nanoparticles (ZnONPs) from Carob and their evaluation for antimicrobial activity in bacteria and fungi. The synthesized ZnONPs showed strong antibacterial activity against Staphylococcus aureus ATCC 25 923 (92%). The NPs inhibited the growth of pathogenic yeast strains, including Candida albicans ATCC90028, Candida krusei ATCC6258, and Candida neoformans ATCC14116, by 90%, 91%, and 82%, respectively, compared to the control. Fungal inhibition zones with the ZnONPs were 88.67% and 90%, respectively, larger for Aspergillus flavus 15UA005 and Aspergillus fumigatus ATCC204305, compared to control fungal growth. This study provides novel information relevant for plant-based development of new and potentially antimicrobial ZnONPs based on extracts. In particular, the development and application of phytogenic nanoparticles enhances the biocompatibility of nano-scale materials, thereby allowing to tune effects to prevent adverse outcomes in non-target biological systems.

Growth, root colonization and nutrient status of Helianthemum sessiliflorum Desf. inoculated with a desert truffle Terfezia boudieri Chatin.

This study aims to investigate the effects of inoculation using Terfezia boudieri Chatin ascospores (ectomycorrhizal fungus) on growth, root colonization and nutrient status of Helianthemum sessiliflorum Desf. seedlings grown in pots on two-soil types (gypseous and sandy loam). Mycorrhizal seedlings had significantly increased their height and leaf number compared to non-mycorrhizal ones. Regardless of mycorrhizal inoculation treatments, the plants growing on gypseous soil showed higher growth as compared to sandy loam one. It appears that inoculation with T. boudieri changed root morphology, increasing branching of first-order lateral roots of H. sessiliflorum seedlings. The highest root mycorrhizal colonization was recorded in inoculated seedlings on sandy loam soil (89%) when compared to gypseous one (52%). N, P and K concentrations in mycorrhizal seedlings were significantly improved by fungal inoculation. It can be concluded that inoculation of H. sessiliflorum with T. boudieri increased growth attributes and improved plant nutritional status.

Factors influencing seed germination of medicinal plant Salvia aegyptiaca L. (Lamiaceae).

Salvia aegyptiaca is a xerophytic perennial herb belongs to the Lamiaceae family commonly used for medicinal purposes. Laboratory experiments were carried out to assess the effects of temperature and salinity on seed germination and recovery responses after transferring to distilled water. Temperatures between 10 and 40 °C seem to be favourable for the germination of this species. Germination was inhibited by either an increase or decrease in temperature from the optimum (30 °C). The highest germination percentages were obtained at 0 mM NaCl; however, the increase of solution osmolalities progressively inhibited seed germination. The germination rate decreased with an increase in salinity for most of tested temperatures, but comparatively higher rates were obtained at 30 °C. Salt stress decreased both the percentage and the rate of germination. An interaction between salinity and temperature yielded no germination at 300 mM NaCl. By experimental transfer to distilled water, S. aegyptiaca seeds that were exposed to moderately saline conditions recovered and keep their ability to germinate mostly at low temperatures. At 300 mM NaCl, germination recovery decreased with increasing temperature and it was completely inhibited at 40 °C.

The effect of sodium chloride salinity on the growth, water status and ion content of Phragmites communis trin.

The present study deal with the physiological behavior of Phragmites communis under salt stress. The effects of salinity on growth, dry weight partitioning, water status and ion content were studied on seedlings of P. communis fed with nutrient solutions containing 0 to 600 mM NaCl. The plants grew best when irrigated with distilled water; biomass production and Relative Growth Rate (RGR) decreased with increasing salinity. Nevertheless, plants were able to produce and allocate dried matter to all their organs even at the highest salt level (600 mM NaCl). The leaves showed the lowest growth activity. Increasing salinity was accompanied by a decrease in seedling water content; aerial parts were more dehydrated than roots. Examination of the K+/Na+ selectivity revealed that salt tolerance of reed plants may be due to its capacity to limit Na+ transport and to enhance K+ transport into aerial parts resulting in a high K/Na ratio. Our results suggest an exclusive behavior towards Na+ as shown by the decreasing Na+ gradients from leaves to roots. It is concluded that Na+ exclusion mechanism appeared to be operative and contributes to salt tolerance of Phragmites.