Photoprotection enhanced by red cell wall pigments in three East Antarctic mosses

BACKGROUND: Antarctic bryophytes (mosses and liverworts) are resilient to physiologically extreme environmental conditions including elevated levels of ultraviolet (UV) radiation due to depletion of stratospheric ozone. Many Antarctic bryophytes synthesise UV-B-absorbing compounds (UVAC) that are localised in their cells and cell walls, a location that is rarely investigated for UVAC in plants. This study compares the concentrations and localisation of intracellular and cell wall UVAC in Antarctic Ceratodon purpureus, Bryum pseudotriquetrum and Schistidium antarctici from the Windmill Islands, East Antarctica. RESULTS: Multiple stresses, including desiccation and naturally high UV and visible light, seemed to enhance the incorporation of total UVAC including red pigments in the cell walls of all three Antarctic species analysed. The red growth form of C. purpureus had significantly higher levels of cell wall bound and lower intracellular UVAC concentrations than its nearby green form. Microscopic and spectroscopic analyses showed that the red colouration in this species was associated with the cell wall and that these red cell walls contained less pectin and phenolic esters than the green form. All three moss species showed a natural increase in cell wall UVAC content during the growing season and a decline in these compounds in new tissue grown under less stressful conditions in the laboratory. CONCLUSIONS: UVAC and red pigments are tightly bound to the cell wall and likely have a long-term protective role in Antarctic bryophytes. Although the identity of these red pigments remains unknown, our study demonstrates the importance of investigating cell wall UVAC in plants and contributes to our current understanding of UV-protective strategies employed by particular Antarctic bryophytes. Studies such as these provide clues to how these plants survive in such extreme habitats and are helpful in predicting future survival of the species studied.

Síndrome de Peutz-Jeghers: novos dados e bases moleculares sobre uma doença rara / The Peutz-Jeghers syndrome: new data and molecular bases on a rare disease

A síndrome de Peutz-Jeghers é uma associação de polipose no trato gastrointestinal do tipo familiar e pigmentação melânica mucocutânea, particularmente nos lábios, mucosa bucal e polpa digital. Há poucas décadas, algumas centenas de casos haviam sido descritos na literatura, o que torna a doença não tão rara. O objetivo deste trabalho foi relatar casos clínicos em que os pacientes eram portadores da síndrome. Em um dos casos, tia e sobrinha evidenciaram a implicação genética da doença. Dados clínicos, bases moleculares e resultados histopatológicos, com a utilização de anticorpos (Ac) monoclonais, mostram a relevância do trabalho. Portadores crônicos da síndrome após décadas, ainda não diagnosticados, procuram o cirurgião-dentista para tratamentos diversos, dando-lhe oportunidade e responsabilidade na detecção da doença, devido ao risco de desenvolvimento de tumores malignos no trato gastrointestinal.

The Peutz-Jeghers syndrome is a familiar association of polyposis in the gastrointestinal tract and melanic mucocutaneous pigmentation, particularly in the lips, oral mucosa and fi ngertips. A few decades few hundred cases had been described in the literature wich makes the disease not so rare. The objective of this study is to report clinical cases where patients were carriers of the syndrome. In one of the cases the aunt and nice showed the genetic implication of the disease. Clinical data, molecular basis and histopathological results with monoclonal antibodies (Ac), show the relevance of this work. Chronic carriers of the syndrome after decades, still undiagnosed, seek the dentist for various treatments giving him the opportunity and responsibility to detect the disease due to the risk of development of malignant tumors in the gastrointestinal tract.

Artificial UV-B induced changes in pigmentation of marine diatom Coscinodiscus gigas.

In vitro studies in marine diatom Coscinodiscus gigas revealed that artificial UV-B radiation (313 nm) at a dose level of 0.4W m(-2) for a continuous period of 3 hours in a UV treatment chamber caused disbursement of chromatophores from their normal loci and resulted in clumping / aggregation of chromatophores exhibiting a phenomenon called UV-B induced syntrophism. It is also understood that such clumping could cause only insignificant reduction in photosynthetic oxygen release.