Steroidal glycoalkaloids (SGAs) such as α-solanine found in solanaceous food plants— as, for example, potato— are antinutritional factors for humans. Comparative coexpression analysis between tomato ...and potato coupled with chemical profiling revealed an array of 10 genes that partake in SGA biosynthesis. We discovered that six of them exist as a cluster on chromosome 7, whereas an additional two are adjacent in a duplicated genomic region on chromosome 12. Following systematic functional analysis, we suggest a revised SGA biosynthetic pathway starting from cholesterol up to the tetrasaccharide moiety linked to the tomato SGA aglycone. Silencing GLYCOALKALOID METABOLISM 4 prevented accumulation of SGAs in potato tubers and tomato fruit. This may provide a means for removal of unsafe, antinutritional substances present in these widely used food crops.
The core genes associated with the biosynthesis of steroidal alkaloids in the Solanaceae are part of metabolic gene clusters. The significance of gene clusters to plants and the potential ...biotechnological application of the recent findings are discussed. Display omitted
•A complete pathway for Solanaceae steroidal alkaloids biosynthesis was proposed.•Steroidal alkaloids core pathway genes are mostly found clustered in the genome.•Clusters might enable transcriptional, post-transcriptional and epigenetic control.•Levels of anti-nutritional glycoalkaloids can now be modified in potato tubers.
Steroidal alkaloids (SAs) and their glycosylated forms (SGAs) are toxic compounds largely produced by members of the Solanaceae and Liliaceae plant families. This class of specialized metabolites serves as a chemical barrier against a broad range of pest and pathogens. In humans and animals, SAs are considered anti-nutritional factors because they affect the digestion and absorption of nutrients from food and might even cause poisoning. In spite of the first report on SAs nearly 200years ago, much of the molecular basis of their biosynthesis and regulation remains unknown. Aspects concerning chemical structures and biological activities of SAs have been reviewed extensively elsewhere; therefore, in this review the latest insights to the elucidation of the SAs biosynthetic pathway are highlighted. Recently, co-expression analysis combined with metabolic profiling revealed metabolic gene clusters in tomato and potato that contain core genes required for production of the prominent SGAs in these two species. Elaborating the knowledge regarding the SAs biosynthetic pathway, the subcellular transport of these molecules, as well as the identification of regulatory and signaling factors associated with SA metabolism will likely advance understanding of chemical defense mechanisms in Solanaceae and Liliaceae plants. It will also provide the means to develop, through classical breeding or genetic engineering, crops with modified levels of anti-nutritional SAs.
Carrier (exciton) multiplication in colloidal InAs/CdSe/ZnSe core−shell quantum dots (QDs) is investigated using terahertz time-domain spectroscopy, time-resolved transient absorption, and ...quasi-continuous wave excitation spectroscopy. For excitation by high-energy photons (∼2.7 times the band gap energy), highly efficient carrier multiplication (CM) results in the appearance of multi-excitons, amounting to ∼1.6 excitons per absorbed photon. Multi-exciton recombination occurs within tens of picoseconds via Auger-type processes. Photodoping (i.e., photoinjection of an exciton) of the QDs prior to excitation results in a reduction of the CM efficiency to ∼1.3. This exciton-induced reduction of CM efficiency can be explained by the twofold degeneracy of the lowest conduction band energy level. We discuss the implications of our findings for the potential application of InAs QDs as light absorbers in solar cells.
Large‐scale, single pass sequencing and parallel gene expression analysis using DNA microarrays were employed for the comprehensive investigation of ripening in strawberry fruit. A total of 1701 cDNA ...clones (comprising 1100 strawberry ESTs and 601 unsequenced cDNAs) obtained from a strawberry (Fragaria×ananassa) ripe fruit cDNA library were displayed on microarrays, and used for monitoring concurrent gene expression in receptacle and achene tissues. Analysis of expression ratios identified 66 out of the 259 (25%) achene‐related clones and 80 out of 182 (44%) receptacle‐related clones with more than a 4‐fold difference in expression between the two tissue types. Half of the achene‐associated genes putatively encode proteins with unknown function, and a large number of the remainder were proteins predicted to form part of the signal and regulation cascades related to achene maturation and acquisition of stress and desiccation tolerance. These included phosphatases, protein kinases, 14‐3‐3 proteins, transcription factors, and others. In the receptacle, key processes and novel genes that could be associated with ripening were identified. Genes putatively encoding proteins related to stress, the cell wall, DNA/RNA/protein, and primary metabolism were highly represented. Apart from providing a global observation on gene expression programmes and metabolic pathways in the developing strawberry, this study has made available a large database and unique information for gene discovery, promoter selection and markers for molecular breeding approaches.
The role glucosinolates play in defending plants against phloem feeders such as aphids and whiteflies is currently not clear as these herbivores may avoid bringing glucosinolates from the phloem sap ...into contact with myrosinase enzymes. Here, we investigated the effects of high levels of aliphatic and indolic glucosinolates on life history traits and detoxification gene expression in two sibling species, B and Q, of the whitefly Bemisia tabaci. High levels of aliphatic glucosinolates decreased the average oviposition rate of both species and reduced the survival and developmental rate of Q nymphs. High levels of indolic glucosinolates decreased the oviposition rate and survival of nymphal stages of the B species and the developmental rate of both species. Molecular analyses revealed two major asymmetries between the B and Q species. First, specific GST genes (BtGST1 and BtGST2) were significantly induced during exposure to indolic glucosinolates only in Q. This may reflect the genes putative involvement in indolic glucosinolates detoxification and explain the species’ good performance on plants accumulating indolic glucosinolates. Second, the constitutive expression of eight of the 10 detoxification genes analysed was higher in the Q species than in the B species. Interestingly, four of these genes were induced in B in response to high levels of glucosinolates. It seems, therefore, that the B and Q species differ in their ‘optimal defence strategy’. B utilizes inducible defences that are profitable if the probability of experiencing the stress is small and its severity is low, while Q invests significant resources in being always ‘ready’ for a challenge.
AbstractA large-scale comprehensive survey of indicator bacteria, pathogen viruses, coliphages, microbial source tracking (MST) indicators, and antibiotic resistance genes was carried out in the ...Shafdan soil aquifer treatment (SAT) of the Tel Aviv, Israel area. The study reveals complete elimination of pathogen viruses—enterovirus, adenovirus, norovirus, parechovirus, and coliphage—and of the bacterial indicators total and fecal coliforms, fecal streptococcus, and microbial source tracking (MST) Bacteroides already in the vadose zone below the percolation basins. Trace levels of antibiotic resistance genes (ARGs) were detected in the recovery wells, but these were also detected in wells not impacted by effluent, suggesting that these genes are associated with native aquifer bacterial communities. This is the first comprehensive survey describing four types of microbial indicators—bacteria, pathogenic viruses, coliphages, and MST—for SAT research, and the first to address the occurrence of antibiotic resistance genes in SAT systems. The results should provide guidance to regulatory agencies regarding the attainable efficiency of optimally designed and operated SAT systems and the monitoring point locations. Most of the pathogen removal occurs in the vadose zone underneath the basins, which can be monitored more rapidly than the water quality in the recovery wells.
Summary
The present study was conducted to review factors affecting the prevalence and concentration of Giardia in raw wastewater. The removal and inactivation efficiency of Giardia by wastewater ...treatment technologies was also reviewed. Data published for the prevalence of Giardia in wastewater and the removal by wastewater treatment plants was reviewed. Giardia cysts are highly prevalent in wastewater in various parts of the world, which may reflect the infection rate in the population. In 23 of 30 (76·6%) studies, all of the tested raw wastewater samples were positive for Giardia cysts at concentrations ranging from 0·23 to 100 000 cysts l−1. The concentration of Giardia in raw wastewater was not affected by the geographical region or the socio‐economic status of the community. Discharge of raw wastewater or the application of raw wastewater for irrigation may result in Giardia transmission. Activated sludge treatment resulted in a one to two orders of magnitude reduction in Giardia, whereas a stabilization pond with a high retention time removed up to 100% of the cysts from wastewater. High‐rate sand filtration, ultrafiltration and UV disinfection were reported as the most efficient wastewater treatment methods for removal and disinfection of Giardia cysts. Wastewater treatment may not totally prevent the environmental transmission of Giardia cysts. The reviewed data show that a combination of wastewater treatment methods may results in efficient removal of Giardia cysts and prevent their environmental transmission.
Significant inter‐ and intraspecific genetic variation exists in duckweed, thus the potential for genome plasticity and manipulation is high. Polyploidy is recognised as a major mechanism of ...adaptation and speciation in plants. We produced several genome‐duplicated lines of Landoltia punctata (Spirodela oligorrhiza) from both whole plants and regenerating explants using a colchicine‐based cocktail. These lines stably maintained an enlarged frond and root morphology. DNA ploidy levels determined by florescence‐activated cell sorting indicated genome duplication. Line A4 was analysed after 75 biomass doublings. Frond area, fresh and dry weights, rhizoid number and length were significantly increased versus wild type, while the growth rate was unchanged. This resulted in accumulation of biomass 17–20% faster in the A4 plants. We sought to determine if specific differences in gene products are found in the genome duplicated lines. Non‐targeted ultra performance LC‐quadrupole time of flight mass spectrometry was employed to compare some of the lines and the wild type to seek identification of up‐regulated metabolites. We putatively identified differential metabolites in Line A65 as caffeoyl hexoses. The combination of directed genome duplication and metabolic profiling might offer a path for producing stable gene expression, leading to altered production of secondary metabolites.
In the framework of the international project “Integrated Concepts for Water Reuse” (Aquarec), an independent task-force composed by water and wastewater utilities professionals, consultants and ...researchers was assigned the task and produced a manual of management practices for water reuse schemes. This paper aims to give an overview of water reuse activities around the world and to outline the specific characteristics of every sectoral use. The paper shows that consolidated experience exists with technology and management practices and that effective and practicable management practices should include a combination of structural, non-structural and managerial techniques. Finally, some critical factors that influence to a large extent the project’s potential sustainability are delineated.
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