Nuclear DNA content in allopolyploid species and synthetic hybrids in the grass genus Paspalum

DNA content was estimated by flow cytometry in seventeen taxa from the Dilatata, Quadrifaria and Paniculata groups of Paspalum and five synthetic hybrids. Results were compared to known genome constitutions and phylogenetic relationships. DNA 2C-values ranged from 1.24 pg in diploid P. juergensii to 3.79 pg in a hexaploid biotype of P. dilatatum. The I genome of three Quadrifaria diploids is 1.2 to 1.5-fold larger than the J genome of P. juergensii (Paniculata). The 2C-values of the IIJJ tetraploids of the Dilatata group are lower than expected based on putative genome donors. Reduction of genome sizes could have occurred after the formation of the allopolyploids of the Dilatata group. The DNA content of all synthetic hybrids is in accordance with the sum of parental C-values. The interactions driving genome downsizing may operate differently during the transition from diploidy to polyploidy than on subsequent increases in ploidy level.     

Identification and characterisation of a novel acylpeptide hydrolase from Sulfolobus solfataricus: structural and functional insights

A novel acylpeptide hydrolase, named APEH-3(Ss), was isolated from the hypertermophilic archaeon Sulfolobus solfataricus. APEH is a member of the prolyl oligopeptidase family which catalyzes the removal of acetylated amino acid residues from the N terminus of oligopeptides. The purified enzyme shows a homotrimeric structure, unique among the associate partners of the APEH cluster and, in contrast to the archaeal APEHs which show both exo/endo peptidase activities, it appears to be a "true" aminopeptidase as exemplified by its mammalian counterparts, with which it shares a similar substrate specificity. Furthermore, a comparative study on the regulation of apeh gene expression, revealed a significant but divergent alteration in the expression pattern of apeh-3(Ss) and apeh(Ss) (the gene encoding the previously identified APEH(Ss) from S. solfataricus), which is induced in response to various stressful growth conditions. Hence, both APEH enzymes can be defined as stress-regulated proteins which play a complementary role in enabling the survival of S. solfataricus cells under different conditions. These results provide new structural and functional insights into S. solfataricus APEH, offering a possible explanation for the multiplicity of this enzyme in Archaea.     

cry1 and GPA1 signaling genetically interact in hook opening and anthocyanin synthesis in Arabidopsis

While studying blue light-independent effects of cryptochrome 1 (cry1) photoreceptor, we observed premature opening of the hook in cry1 mutants grown in complete darkness, a phenotype that resembles the one described for the heterotrimeric G-protein α subunit (GPA1) null mutant gpa1. Both cry1 and gpa1 also showed reduced accumulation of anthocyanin under blue light. These convergent gpa1 and cry1 phenotypes required the presence of sucrose in the growth media and were not additive in the cry1 gpa1 double mutant, suggesting context-dependent signaling convergence between cry1 and GPA1 signaling pathways. Both, gpa1 and cry1 mutants showed reduced GTP-binding activity. The cry1 mutant showed wild-type levels of GPA1 mRNA or GPA1 protein. However, an anti-transducin antibody (AS/7) typically used for plant Gα proteins, recognized a 54?kDa band in the wild type but not in gpa1 and cry1 mutants. We propose a model where cry1-mediated post-translational modification of GPA1 alters its GTP-binding activity.     

Cytogenetics as a tool for triatomine species distinction (Hemiptera-Reduviidae).

Several cytogenetic traits were tested as species diagnostic characters on five triatomine species: Rhodnius pictipes, R. nasutus, R. robustus, Triatoma matogrossensis and T. pseudomaculata. Four of them are described for the first time. The detailed analysis of the meiotic process and the application of C-banding allowed us to identify seven cytogenetic characters which result useful to characterize and differentiate triatomine species.     

Effects of pure n-alkanes and crude oil on bacterial phospholipid classes and molecular species determined by electrospray ionization mass spectrometry

Phospholipids are major components of bacterial membrane. Furthermore, the growth in vitro on xenobiotics such as n-alkanes, aromatic compounds or alkanols bring about to a bacterial membrane adaptive response. Concerning this work, we studied the membrane lipid composition of a hydrocarbon-degrading gram-positive bacterium (Corynebacterium sp.) on a soluble substrate and we detected four different phospholipid classes: phosphatidylglycerol, phosphatidylinositol, cardiolipin and acyl phosphatidylglycerol. In addition, a study of the lipid composition was performed after an in vitro culture on either pure n-alkane or crude oil. The growths on such hydrophobic substrates showed major qualitative and quantitative modifications. In the case of a growth on either heneicosane or crude oil, an increase of odd-numbered fatty acids was observed. Furthermore, the phospholipid polar head group composition was highly influenced by the crude oil addition. These modifications were, respectively, interpreted as the consequence of hydrocarbon assimilation and membrane fluidity adaptation. Finally, Corynebacterium sp. was taken back on the initial ammonium acetate substrate in order to determine its restoration abilities after a petroleum contamination.     

Ultraviolet B radiation enhances a phytochrome-B-mediated photomorphogenic response in Arabidopsis

Ultraviolet B radiation (UV-B, 290-315 nm) can cause damage and induce photomorphogenic responses in plants. The mechanisms that mediate the photomorphogenic effects of UV-B are unclear. In etiolated Arabidopsis seedlings, a daily exposure to 2.5 h of UV-B enhanced the cotyledon opening response induced by a subsequent red light (R) pulse. An R pulse alone, 2.5 h of UV-B terminated with a far-red pulse, or 2.5 h of continuous R caused very little cotyledon opening. The enhancing effect of UV-B increased with fluence rate up to approximately 7.58 micromol m(-2) s(-1); at higher fluence rates the response to UV-B was greatly reduced. The phyA, phyA cry1, and cry1 cry2 mutants behaved like the wild type when exposed to UV-B followed by an R pulse. In contrast, phyB, phyB cry1, and phyB phyA mutants failed to open the cotyledons. Thus, phytochrome B was required for the cotyledon opening response to UV-B --> R treatments, whereas phytochrome A and cryptochromes 1 and 2 were not necessary under the conditions of our experiments. The enhancing effect of low doses of UV-B on cotyledon opening in uvr1 uvr2 and uvr1 uvr3 mutants, deficient in DNA repair, was similar to that found in the wild type, suggesting that this effect of UV-B was not elicited by signals derived from UV-B-induced DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts). We conclude that low doses of UV-B, perceived by a receptor system different from phytochromes, cryptochromes, or DNA, enhance a de-etiolation response that is induced by active phytochrome B.     

Biological succession on silicone fouling‐release surfaces: Long‐term exposure tests in the harbour of ischia,Italy

A static test site was set up in the Harbour of Ischia (Gulf of Naples, Italy) to investigate the antifouling effectiveness of newly developed non‐polluting coatings. Two‐year exposure experiments were performed on sets of panels coated with silicone‐based coatings, and results were compared both to sets of panels coated with toxic agents, and non‐toxic epoxydic compounds. Abiotic factors, strength of adhesion of the temporal dynamics of succession of foulers were analyzed throughout the period of immersion. Brown algae constantly represented the “border point”; between the early community, dominated by sume, micro‐ and macroalgae, and the late community, mainly represented by bryozoans and molluscs, as well as polychaetes, sponges and tunicates. Brown algae, such as Ectocarpus siliculosus, tunicates (mainly Botryllus schlossen) and polychaetes (Hydroides elegans, Pileolaria pseudomilitaris) were demonstrated to be key species, triggering the community and influencing its development. Light was the main abiotic factor discriminating the community on the two sides of panels exposed to different irradiances. The best performing coatings (silicone easy release coatings without additives) substantially influenced community structure, shifting it to the earliest stages of colonization. Silicone coatings proved to be unsuitable for colonization by organisms typical of mature communities, due to their low energy surfaces. The results of the present paper demonstrate that silicone coatings technology represents an alternative to the use of biocidal antifouling paints.