Molecular characterization of Lebanese olive germplasm

Lebanon, an East Mediterranean country, does not have a comprehensive reference national olive collection. A report published 30 years ago indicated the presence of four Lebanese varieties, but the confusion regarding these varieties was discussed then and is still prevalent today hindering prospects for conserving and exploring the national germplasm. This study assessed the existing in situ diversity of old Lebanese olive groves using simple sequence repeat (SSR) and amplified fragment length polymorphisms (AFLP). Trees (140) were collected from 14 groves located in the four traditional olive areas. Analysis was based on 22 polymorphic alleles produced from six SSR primers, and on 135 polymorphic AFLP fragments. SSR and AFLP did not yield consistent results in terms of level of polymorphism, with SSR detecting higher variation than AFLP. On the other hand, both clustered trees based on geographic provenance. AFLP coefficient of similarity between trees ranged between 0.70 and 0.99 indicating the possible presence of varieties since some values fall within reported intervarietal ranges of 0.65 to 0.84. SSR unveiled the presence of nine different genotypes: four corresponding each to a provenance and five consisting of single trees characterized by the presence of less frequent alleles with an average of 0.33. Results also revealed a high incidence of clones greater than 90% in three of the four provenances. The findings of this study point for the need to plan for a sampling strategy that takes into consideration geographic provenances.     

First archaeological evidence of banana cultivation in central Africa during the third millennium before present

Phytoliths recovered from refuse pits excavated in central Cameroon and dated to ca 2500 B.P. have been positively identified for the first time in Africa as derived from Musa the cultivated banana, after a comparative study of Musa and Ensete phytoliths. This discovery provides archaeologists with unequivocal proof of early agriculture in central Africa. Furthermore, the presence of banana in Cameroon much earlier than previously assumed could explain how agriculture spread through the rain forest. Lastly, as Musa is of Asian origin, this study provides the first concrete evidence of contacts across the Indian Ocean a millennium earlier than currently accepted. Received July 12, 1999 / Accepted May 4, 2000     

Coexistence of Flexibility and Stability of Proteins: An Equation of State

We consider a recently suggested “equation of state” for natively folded proteins, and verify its validity for a set of about 5800 proteins. The equation is based on a fractal viewpoint of proteins, on a generalization of the Landau-Peierls instability, and on a marginal stability criterion. The latter allows for coexistence of stability and flexibility of proteins, which is required for their proper function. The equation of state relates the protein fractal dimension , its spectral dimension , and the number of amino acids N. Using structural data from the protein data bank (PDB) and the Gaussian network model (GNM), we compute and for the entire set and demonstrate that the equation of state is well obeyed. Addressing the fractal properties and making use of the equation of state may help to engineer biologically inspired catalysts.     

Gq protein-induced apoptosis is mediated by AKT kinase inhibition that leads to protein kinase C-induced c-Jun N-terminal kinase activation

G(q) protein-coupled receptors (G(q)PCRs) regulate various cellular processes, including mainly proliferation and differentiation. In a previous study we found that in prostate cancer cells, the G(q)PCR of gonadotropin-releasing hormone (GnRH) induces apoptosis by reducing the PKC-dependent AKT activity and elevating JNK phosphorylation. Because it was thought that G(q)PCRs mainly induce activation of AKT, we first undertook to examine how general this phenomenon is. In a screen of 21 cell lines we found that PKC activation results in the reduction of AKT activity, which correlates nicely with JNK activation and in some cases with apoptosis. To understand further the signaling pathways involved in this stimulation, we studied in detail SVOG-4O and αT3-1 cells. We found that prostaglandin F2α and GnRH agonist (GnRH-a) indeed induce significant Gα(q)- and PKC-dependent apoptosis in these cells. This is mediated by two signaling branches downstream of PKC, which converge at the level of MLK3 upstream of JNK. One branch consists of c-Src activation of the JNK cascade, and the second involves reduction of AKT activity that alleviates its inhibitory effect on MLK3 to allow the flow of the c-Src signal to JNK. At the MAPKK level, we found that the signal is transmitted by MKK7 and not MKK4. Our results present a general mechanism that mediates a G(q)PCR-induced, death receptor-independent, apoptosis in physiological, as well as cancer-related systems.     

Pleiotropic signaling pathways orchestrate yeast development

Developmental phenotypes in Saccharomyces cerevisiae and related yeasts include responses such as filamentous growth, sporulation, and the formation of biofilms and complex colonies. These developmental phenotypes are regulated by evolutionarily conserved, nutrient-responsive signaling networks. The signaling mechanisms that control development in yeast are highly pleiotropic--all the known pathways contribute to the regulation of multiple developmental outcomes. This degree of pleiotropy implies that perturbations of these signaling pathways, whether genetic, biochemical, or environmentally induced, can manifest in multiple (and sometimes unexpected) ways. We summarize the current state of knowledge of developmental pleiotropy in yeast and discuss its implications for understanding functional relationships.