11 research outputs found
The Medicago truncatula sucrose transporter family
In plants, long distance transport of sugars from photosynthetic source leaves to sink organs comprises
different crucial steps depending on the species and organ types. Sucrose, the main carbohydrate for long
distance transport is synthesized in the mesophyll and then loaded into the phloem. After long distance
transport through the phloem vessels, sucrose is finally unloaded towards sink organs. Alternatively, sugar
can also be transferred to non-plant sinks and plant colonization by heterotrophic organisms increases the
sink strength and creates an additional sugar demand for the host plant. These sugar fluxes are coordinated
by transport systems. Main sugar transporters in plants comprise sucrose (SUTs) and monosaccharide
(MSTs) transporters which constitute key components for carbon partitioning at the whole plant level and
in interactions with fungi. Although complete SUTs and MSTs gene families have been identified from the
reference Dicot Arabidopsis thaliana and Monocot rice (Oriza sativa), sugar transporter families of the
leguminous plant Medicago truncatula, which represents a widely used model for studying plant-fungal
interactions in arbuscular mycorrhiza (AM), have not yet been investigated.
With the recent completion of the M. truncatula genome sequencing as well as the release of
transcriptomic databases, monosaccharide and sucrose transporter families of M. truncatula were identified
and now comprise 62 MtMSTs and 6 MtSUTs. I focused on the study of the newly identified MtSUTs at a
full family scale; phylogenetic analyses showed that the 6 members of the MtSUT family distributed in all
three Dicotyledonous SUT clades; they were named upon phylogenetic grouping into particular clades:
MtSUT1-1, MtSUT1-2, MtSUT1-3, MtSUT2, MtSUT4-1 and MtSUT4-2. Functional analyses by yeast
complementation and expression profiles obtained by quantitative RT-PCR revealed that MtSUT1-1 and
MtSUT4-1 are H+/sucrose symporters and represent key members of the MtSUT family. Conservation of
transport capacity between orthologous leguminous proteins, expression profiles and subcellular
localization compared to previously characterized plant SUTs indicate that MtSUT1-1 is the main protein
involved in phloem loading in source leaves whilst MtSUT4-1 mediates vacuolar sucrose export for
remobilization of intracellular reserve.
The AM symbiosis between plants and fungi from the phylum Glomeromycota is characterized by trophic
exchanges between the two partners. The fungus supplies the autotrophic host with nutrients and thereby
promotes plant growth. In return, the host plant provides photosynthate (sugars) to the heterotrophic
symbiont. Here, sugar fluxes from plant source leaves towards colonized sink roots in the association
between the model leguminous plant M. truncatula and the arbuscular mycorrhizal fungus (AMF) Glomus
intraradices were investigated. Sugar transporter candidates from both the plant and fungal partners
presenting differential expression profiles using available transcriptomic tools were pinpointed. Gene
expression profiles of MtSUTs and sugar quantification analyses upon high and low phosphorus nutrient
supply and inoculation by the AMF suggest a mycorrhiza-driven stronger sink in AM roots with a finetuning
regulation of MtSUT gene expression. Conserved regulation patterns were observed for orthologous
SUTs in response to colonization by glomeromycotan fungi.
In parallel, a non-targeted strategy consisting in the development of a M. truncatula - G. intraradices
expression library suitable for yeast functional complementation and screening of symbiotic marker genes,
similar to the approach that led to the identification of the first glomeromycotan hexose transporter
(GpMST1), has been developed in this study.
Taken together, with the identification, functional characterization and gene expression pattern of sugar
transporter families, a more complete picture of sugar fluxes in the AM symbiosis has begun to emerge.
This study opens new perspectives by identifying interesting candidate genes involved in sugar partitioning
at both the plant and fungal levels and at the symbiotic interface in the widely used AM symbiosis model
between M. truncatula and G. intraradices
Synthesis of new pyrazolium based tunable aryl alkyl ionic liquids and their use in removal of methylene blue from aqueous solution
In this study, two new pyrazolium based tunable aryl alkyl ionic liquids, 2-ethyl-1-(4-methylphenyl)-3,5- dimethylpyrazolium tetrafluoroborate (3a) and 1-(4-methylphenyl)-2-pentyl-3,5-dimethylpyrazolium tetrafluoroborate (3b), were synthesized via three-step reaction and characterized. The removal of methylene blue (MB) from aqueous solution has been investigated using the synthesized salts as an extractant and methylene chloride as a solvent. The obtained results show that MB was extracted from aqueous solution with high extraction efficiency up to 87 % at room temperature at the natural pH of MB solution. The influence of the alkyl chain length on the properties of the salts and their extraction efficiency of MB was investigated
Time Localization of Abrupt Changes in Cutting Process using Hilbert Huang Transform
Cutting process is extremely dynamical process influenced by different phenomena such as chip formation, dynamical responses and condition of machining system elements. Different phenomena in cutting zone have signatures in different frequency bands in signal acquired during process monitoring. The time localization of signal’s frequency content is very important.
An emerging technique for simultaneous analysis of the signal in time and frequency domain that can be used for time localization of frequency is Hilbert Huang Transform (HHT). It is based on empirical mode decomposition (EMD) of the signal into intrinsic mode functions (IMFs) as simple oscillatory modes. IMFs obtained using EMD can be processed using Hilbert Transform and instantaneous frequency of the signal can be computed.
This paper gives a methodology for time localization of cutting process stop during intermittent turning. Cutting process stop leads to abrupt changes in acquired signal correlated to certain frequency band. The frequency band related to abrupt changes is localized in time using HHT. The potentials and limitations of HHT application in machining process monitoring are shown
Infections
• Infections with viruses, bacteria, and macroparasites have been identified as strong risk factors for specific cancers. • Overall, about 2 million (16%) of the total of 12.7 million new cancer cases in 2008 are attributable to infections. This fraction varies 10-fold by region; it is lowest in North America, Australia, and New Zealand (≤ 4%) and highest in sub-Saharan Africa (33%). • Helicobacter pylori, hepatitis B and C viruses, and human papillomaviruses are responsible for 1.9 million cancer cases globally, including mainly gastric, liver, and cervical cancer, respectively. • Infection with HIV substantially increases the risk of virusassociated cancers, through immunosuppression. • Application of existing methods for infection prevention, such as vaccination, safe injection practices, and safe sexual behaviour, or antimicrobial and antiparasite treatments could have a major impact on the future burden of cancer worldwide