[Lcefiec] SEMINARIOS QB-IQUIBICEN- Miér. 18 dic- Invitados Especiales

[Cybele García]

--------------------------------------------------------------------------

Estimados Colegas,

Con motivo de la visita de Investigadores Argentinos radicados en el
exterior, el próximo Miércoles 18 de diciembre los invitamos a participar
de 2 seminarios especiales:


11:30 hs- Carla Saleh,Ph.D- Pasteur institute of Paris, France.

"RNAi and reverse transcription control RNA virus persistence in the insect
model Drosophila".



15:00 hs- Pablo I. Nikel- Systems and Synthetic Biology Program, Centro
Nacional de Biotecnología (CNB-CSIC)- Madrid 28045, Spain

"Defining the metabolic itinerary of hexoses in environmental bacteria:
the Entner-Doudoroff pathway empowers Pseudomonas putida with high
resistance to oxidative stress"


----------------------------------------------------------------------------


11:30 hs

 "RNAi and reverse transcription control RNA virus persistence in the insect
model Drosophila".

 Carla Saleh,Ph.D- Pasteur institute of Paris, France.

How persistent viral infections are established and maintained is widely
debated and remains largely misunderstood. We show here that RNA virus
persistence in Drosophila is achieved through the combined action of
endogenous cellular reverse transcriptase activities and of the RNA
interference pathway. Fragments of diverse RNA viruses are reverse
transcribed early during infection, resulting in DNA forms embedded within
retrotransposon sequences. These viral-retrotransposon DNA chimeras produce
transcripts that are processed by the RNAi machinery, which in turn inhibits
viral replication. Conversely, inhibition of reverse transcription hinders
the appearance of chimeric DNAs and prevents persistence. Our results reveal
a cooperative function for retrotransposons and antiviral RNAi in the
control of lethal acute infection in order to reach viral persistence.

Invitan: Daniel Compagno y Diego Laderach

----------------------------------------------------------------------------
15:00 hs

"Defining the metabolic itinerary of hexoses in environmental bacteria:
the Entner-Doudoroff pathway empowers Pseudomonas putida with high
resistance to oxidative stress"

Pablo I. Nikel- Systems and Synthetic Biology Program, Centro Nacional de
Biotecnología (CNB-CSIC)- Madrid 28045, Spain
E-mail: pablo.nikel at cnb.csic.es


Glucose catabolism in the soil bacterium Pseudomonas putida is carried out
exclusively through the Entner-Doudoroff (ED) pathway due to the absence
of any 6-phosphofructokinase able to establish a complete
Embden-Meyerhof-Parnas (EMP) glycolytic route. In an effort to activate
the EMP pathway
in this bacterium, we transferred the pfkA gene from E. coli to a P.
putida wild-type strain as well as to an eda mutant, i.e., lacking
2-keto-3-deoxy-6-phosphogluconate aldolase, an essential component of the
ED pathway. PfkAE. coli was successfully expressed in P. putida KT2440 but
it failed to redirect the carbon flow from the ED route towards the EMP
pathway, suggesting that ED is essential for sugar catabolism in this
bacterium. Furthermore, the presence of PfkAE. coli was detrimental for
growth on
both glycolytic and gluconeogenic C sources. To understand this fact, we
analyzed the energy status and the redox ratios of cells growing on
different substrates (glucose, fructose, and succinate) and
conditionally expressing pfkAE. coli. The results showed that the ATP
levels and the pools of reduced nicotinamide adenine dinucleotides,
especially the NADPH/NADP+ ratio, were decreased by the action of the
heterologous enzyme. Furthermore, P. putida cells carrying PfkAE. coli
became highly sensitive
to the oxidative stressors diamide and hydrogen peroxide, the response to
which is very demanding of NADPH. The inhibitory effect of PfkAE. coli
could in part be relieved by supplying methionine, the synthesis of which
consumes a significant portion of intracellular NADPH. Addition of
substrates of the
pentose phosphate pathway had no influence on the deleterious outcome of
PfkAE. coli, indicating that these effects are not due to a shortage of
building blocks. Taken together, these results expose the role of the ED
pathway for generating the redox currency (NADPH) that is required for
counteracting oxidative stress. It is thus likely that environmental
bacteria that favor the ED pathway over the EMP pathway do so in order to
gear their aerobic metabolism to endure oxidative-related insults.

Invita: Beatriz Mendez

----------------------------------------------------------------------------

Los esperamos!
Adriana De Siervi
Javier Cotignola
Cybele García