Distinciones para el CEFOBI en el Congreso SAIB 2019

Nuestras becarias fueron distinguidas en el LV Congreso de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular, realizado del 5 al 8 de noviembre de 2019 en Salta:

 

Lic. Silvana Righini (Mejor Mostración, Sección Plantas)

ZMS5H, A NOVEL ENZYME INVOLVED IN SALICYLIC ACID HYDROXYLATION

Righini S, Serra P, Falcone Ferreyra ML, Casati P.

Centro de Estudios Fotosintéticos y Bioquímicos, Universidad Nacional de Rosario.

E-mail: righini@cefobi-conicet.gov.ar
 

Salicylic acid (SA) has been described as an important signaling molecule in plants, regulating growth, development, senescence and responses to biotic and abiotic stresses. Levels of salicylic acid are regulated not only by activation of its biosynthetic pathway, but also through its modification by metabolic modifications, such as glycosylation, methylation, amino acid conjugation, and hydroxylation. Hydroxylated SA is the major degradation product of SA. Recently, the A. thaliana enzyme catalyzing SA to 2,3-dihydroxybenzoic acid (2,3-DHBA; AtS3H) has been identified, and SA was found to accumulate in s3h mutants. In this study, we report the discovery and functional characterization of a novel maize salicylic acid 5-hydroxylase (ZmS5H), a 2-oxoglutarate dependent dioxygenase that catalyzes the formation of 2,5-DHBA by hydroxylating SA at the C5 position of its phenyl ring. Once identified, we carried out in vitro activity assays in order to kinetically characterize this enzyme. His-tagged ZmS5H was heterologously expressed in Escherichia coli and then purified. The reaction product 2,5-DHBA was identified by HPLC by comparison with authentic standards. Interestingly, according to sequence similarity analysis, ZmS5H and AtS3H are closely evolutionarily related, though we could not identify 2,3-DHBA as a product of the studied reaction. Kinetic parameters of the recombinant ZmS5H were also determined by HPLC. In addition, its activity in planta was demonstrated, as transgenic Arabidopsis plants expressing ZmS5H were more susceptible to P. syringae pv tomato DC3000 pathogen infection than WT plants, suggesting that these plants would have decreased SA levels due to higher hydroxylation of the hormone. In order to further confirm this, we investigated the expression level of three different genes modulated by SA in s3h, wild-type and transgenic Arabidopsis plants expressing ZmS5H that were treated with this hormone compared to plants treated with mock solution. PR1, EDS-1 and SAG13 showed a decreased expression level in plants overexpressing ZmS5H compared to s3h mutants and wild-type plants, suggesting that in fact ZmS5H hydroxylates SA in planta. We are now analyzing a possible crosstalk between SA hydroxylation and flavonoids synthesis, a model proposed in our lab based in previous results. So far, transgenic plants expressing two different maize flavone synthases recently characterized, (ZmFNSI and ZmFNSII), which accumulate flavones, in a mutant s3h background, show increased susceptibility towards infection with P. syringae compared to wild-type and mutant plants, suggesting that flavones regulate SA levels in vivo.

 
 

Lic. María Belén Velazquez (Mejor Póster, Sección Biología Vegetal)

THE SECRETOME OF THE GREEN ALGA SCENEDESMUS SP.

Velázquez MB, Barchiesi J, Gomez-Casati DG, Busi, MV

Centro de Estudios Fotosintéticos y Bioquímicas, CEFOBI – CONICET, UNR, Rosario, Argentina

E-mail: busi.conicet@gmail.com
 

The generation of food wastes includes from agricultural scale, passing by industrial factories and up to trade and domestic uses. The principal component of wasted forest is lignocellulose, the most abundant natural biopolymer and cheap renewable energy and carbon resources, which mainly is composed of cellulosic and lignin materials. The use of fermentable sugars produced from these materials by enzymatic treatments would add value to these wastes. Nevertheless, no practical process has still been reported for the enzymatic hydrolysis of cellulose. The main reason for this is the high cost of the required enzyme, because free cellulase presents low specific activity, is susceptible to inactivation and difficult to recycle. Cellulase is mostly studied from microbes, more commonly from fungal sources than bacterial. However, there are fewer reports of cellulase from algae. Obtaining these hydrolytic enzymes from algae would help to reduce CO2 emissions and represents economic advantages due to algae are the organisms with the higher photosynthetic yield, and can be grown in closed containers (photobioreactors) or tanks in fields not suitable for agriculture by using waste products such as derivatives of wastewater treatment and flue gas as nutrients. At the same time, the determination of the optimal conditions for its higher photosynthetic efficiency would help to increase the productivity in microalgae, which could be used to increase the food and/or biofuels production. The relationship between photoprotective thermal dissipation and productivity is the key for a biorefinery to manage to compete with petroleum products and materials. Recently, we have detected the presence of extracellular cellulase activity in photoheterotrophic microalgae of fresh water. This work is based on Scenedesmus quadricauda strain. It is a genus of green algae, freshwater, not mobile, which are usually grouped forming colonies of four cells. For the evaluation of the suitable conditions for cellulose secretion we grew the algae at different temperatures (range 4 to 30 °C) and acidity (pH range 3 to 7) in agar plates containing TAP, TAP-MINIMUM and B3N medium in presence and absence of carboxymethyl cellulose (CMC) and with or without light. After five days the plate was revealed with congo red. The results demonstrate that cellulolytic activity can be inducible by substrates, since activity is only observed in those media supplemented with CMC. The identification and molecular characterization of these cellulases is being carried out because they constitute biotechnological targets for the treatment of effluents, CO2 capture and production of biofuels.

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