Plant senescence and proteolysis: two processes with one destiny

Abstract Senescence-associated proteolysis in plants is a complex and controlled process, essential for mobilization of nutrients from old or stressed tissues, mainly leaves, to growing or sink organs. Protein breakdown in senescing leaves involves many plastidial and nuclear proteases, regulators, different subcellular locations and dynamic protein traffic to ensure the complete transformation of proteins of high molecular weight into transportable and useful hydrolysed products. Protease activities are strictly regulated by specific inhibitors and through the activation of zymogens to develop their proteolytic activity at the right place and at the proper time. All these events associated with senescence have deep effects on the relocation of nutrients and as a consequence, on grain quality and crop yield. Thus, it can be considered that nutrient recycling is the common destiny of two processes, plant senescence and, proteolysis. This review article covers the most recent findings about leaf senescence features mediated by abiotic and biotic stresses as well as the participants and steps required in this physiological process, paying special attention to C1A cysteine proteases, their specific inhibitors, known as cystatins, and their potential targets, particularly the chloroplastic proteins as source for nitrogen recycling

1,500-year cycle in the Arctic Oscillation identified in Holocene Arctic sea-ice drift

Weather and climate in the Northern Hemisphere is profoundly affected by the Arctic Oscillation, a quasi-periodic fluctuation in atmospheric pressure that occurs on interannual to interdecadal timescales. Reconstructions of the Arctic Oscillation over longer timescales have suggested additional centennial- to millennial-scale variations in the phase of the oscillation, but often with conflicting results. Here we assess patterns of sea-ice drift in the Arctic Ocean over the past 8,000 years by geochemically determining the source of ice-rafted iron grains in a sediment core off the coast of Alaska. We identify pulses of sediment carried by sea ice from the Kara Sea, which can reach the coast of Alaska only during a strongly positive Arctic Oscillation. On the basis of these observations, we construct a record of the Arctic Oscillation phase, and identify a 1,500-year periodicity similar to that found in Holocene records of ice-rafted debrisin the North Atlantic, distinct from a 1,000-year cycle that has been found in total solar irradiance. We conclude that the 1,500-year cycle in the Arctic Oscillation arises from either internal variability of the climate system or as an indirect response to low-latitude solar forcing.</p

Antiproliferative and Cytotoxic Activities

Cancer is a genetic disease, affecting many people worldwide.Chemotherapy is routinely used for cancer treatment. However, this therapeuticapproach is not always effective due to the development of cell resistance and toxiceffects. Plants are a reservoir of natural chemicals with chemoprotective potentialagainst cancer and with low adverse effects. While some drugs from natural originare currently used for cancer treatment, others are being studied. Among the compoundsisolated from plants, sesquiterpene lactones are very promising anticanceragents, which are widely being studied in different models of cancer in vitro andin vivo, and some clinical trials are being performed. Sesquiterpene lactones arevery attractive compounds to be used as antitumoral therapy due to the diversemechanisms of action through which they exert their effects. Among suchmechanismsare their capacity to interfere with the generation of reactive oxygenspecies, the epigenetic modulation of gene expression, the targeting of the sarco-/endoplasmic reticulum calcium ATPase pump, and the activation of the NF-kB andthe p53 signaling pathways. The latter mechanisms could be important to reduce thedevelopment of drug resistance by tumor cells. Sesquiterpene lactones can alsoinhibit angiogenesis and metastasis.Fil: Anesini, Claudia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Alonso, Maria del Rosario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Martino, Renzo Fabricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentin