Haemolysis has been used as an initial selection criterion for the primary isolation of surfactant-producing bacteria. Only 37 of 492 strains of different origins had haemolytic activity. These 37 strains, together with 49 non-haemolytic ones chosen at random, were studied for surface activity. Only five strains, all of them haemolytic, tested positive. Haemolysis and biosurfactant-production are thus probably associated.

Ultraviolet-B radiation (UV-B, 280–315 nm) is an important environmental signal that regulates growth and development in plants. Two dose-dependent UV-B response pathways were described in plants: a specific one, mediated by UVR8 (the specific UV-B receptor) and an unspecific one, activated by the oxidative damage produced by radiation. The constitutively expressed receptor appears inactive as a dimer, with the two monomers dissociating upon UV-B irradiation. The monomer then interacts with COP1, an ubiquitin ligase, hindering its ability to poly-ubiquitinate transcriptional factor HY5, thus averting its degradation and activating the photomorphogenic response. HY5 induces the synthesis of proteins RUP1 and RUP2, which interact with UVR8, releasing COP1, and inducing the re-dimerization of UVR8. This mechanism has been thoroughly characterized in Arabidopsis, where studies have demonstrated that the UVR8 receptor is key in UV-B response. Although Arabidopsis importance as a model plant many mechanisms described in this specie differ in other plants. In this paper, we review the latest information regarding UV-B response mediated by UVR8 in different species, focusing on the differences reported compared to Arabidopsis. For instance, UVR8 is not only induced by UV-B but also by other agents that are expressed differentially in diverse tissues. Also, in some of the species analyzed, proteins with low homology to RUP1 and RUP2 were detected. We also discuss how UVR8 is involved in other developmental and stress processes unrelated to UV-B. We conclude that the receptor is highly versatile, showing differences among species.

Polyploidy, defined as the coexistence of three or more complete sets of chromosomes in an organism’s cells, is considered as a pivotal moving force in the evolutionary history of vascular plants and has played a major role in the domestication of several crops. In the last decades, improved cultivars of economically important species have been developed artificially by inducing autopolyploidy with chemical agents. Studies on diverse species have shown that the anatomical and physiological changes generated by either natural or artificial polyploidization can increase tolerance to abiotic and biotic stresses as well as disease resistance, which may positively impact on plant growth and net production. The aim of this work is to review the current literature regarding the link between plant ploidy level and tolerance to abiotic and biotic stressors, with an emphasis on the physiological and molecular mechanisms responsible for these effects, as well as their impact on the growth and development of both natural and artificially generated polyploids, during exposure to adverse environmental conditions. We focused on the analysis of those types of stressors in which more progress has been made in the knowledge of the putative morpho-physiological and/or molecular mechanisms involved, revealing both the factors in common, as well as those that need to be addressed in future research.

No abstract

No abstract

No abstract

No abstract

Berberis buxifolia Lam., known as "Calafate", is a plant native to Argentina that exhibits antimicrobial activity. This biological activity is attributed to the isoquinoline alkaloid berberine. The aim of this research was to test the antimicrobial properties of different extracts of this species, taking berberine as the reference molecule, and to examine if the expression of bacterial multidrug resistance (MDR) efflux pumps could be responsible for possible resistance mechanisms. To this end, a wild-type and a mutant strain of Staphylococcus aureus with a defective MDR efflux pump were used and the minimum inhibitory concentrations of the extracts were determined. The studies were carried out with infusions of in vivo shoots and "Calafate" commercial tea, as well as with the media derived from shoot cultures incubated with different plant growth regulators (thidiazuron, picloram, and jasmonic acid). As far as antimicrobial activity is concerned, all the extracts tested were significantly more effective than berberine standard. "Calafate" commercial tea and shoot tea had inhibitory concentrations similar to the one observed for ampicillin standard. The media from the shoot cultures, however, were significantly more effective than all the others, particularly the one derived from jasmonic acid, suggesting the presence of compounds that could be acting synergistically with berberine. There were no differences in antimicrobial activity against the wild-type and the mutant S. aureus; no definite conclusions could be drawn concerning the relationship between MDR pumps and possible pathogen resistance to extracts of B. buxifolia.