Fatty Acid Diversity is Not Associated with Neutral Genetic Diversity in Native Populations of the Biodiesel Plant Jatropha curcas L.

Jatropha curcas L. (Euphorbiaceae) is a shrub native to Mexico and Central America, which produces seeds with a high oil content that can be converted to biodiesel. The genetic diversity of this plant has been widely studied, but it is not known whether the diversity of the seed oil chemical composition correlates with neutral genetic diversity. The total seed oil content, the diversity of profiles of fatty acids and phorbol esters were quantified, also, the genetic diversity obtained from simple sequence repeats was analyzed in native populations of J. curcas in Mexico. Using the fatty acids profiles, a discriminant analysis recognized three groups of individuals according to geographical origin. Bayesian assignment analysis revealed two genetic groups, while the genetic structure of the populations could not be explained by isolation‐by‐distance. Genetic and fatty acid profile data were not correlated based on Mantel test. Also, phorbol ester content and genetic diversity were not associated. Multiple linear regression analysis showed that total oil content was associated with altitude and seasonality of temperature. The content of unsaturated fatty acids was associated with altitude. Therefore, the cultivation planning of J. curcas should take into account chemical variation related to environmental factors.     

Identification of a large cluster of coiled coil-nucleotide binding site–leucine rich repeat-type genes from the Rps1 region containing Phytophthora resistance genes in soybean

Fifteen Rps genes confer resistance against the oomycete pathogen Phytophthora sojae, which causes root and stem rot disease in soybean. We have isolated a disease resistance gene-like sequence from the genomic region containing Rps1-k. Four classes of cDNA of the sequence were isolated from etiolated hypocotyl tissues that express the Rps1-k-encoded Phytophthora resistance. Sequence analyses of a cDNA clone showed that the sequence is a member of the coiled coil-nucleotide binding site–leucine rich repeat (CC-NBS–LRR)-type of disease resistance genes. It showed 36% identity to the recently cloned soybean resistance gene Rpg1-b, which confers resistance against Pseudomonas syringae pv. glycinea, and 56% and 38% sequence identity to putative resistance gene sequences from lotus and Medicago truncatula, respectively. The soybean genome contains about 38 copies of the sequence. Most of these copies are clustered in approximately 600 kb of contiguous DNA of the Rps1-k region. We have identified a recombinant that carries both rps1-k- and Rps1-k-haplotype-specific allelomorphs of two Rps1-k-linked molecular markers. An unequal crossover event presumably led to duplication of alleles for these two physically linked molecular markers. We hypothesize that the unequal crossing over was one of the mechanisms involved in tandem duplication of CC-NBS–LRR sequences in the Rps1-k region.N.N. Narayanan, H. Gao, D.K. Santra, and S.S. Salimath contributed equally to this work.     

Synaptic transfer by human gamma delta T cells stimulated with soluble or cellular antigens

B, alpha beta T, and NK lymphocytes establish immunological synapses (IS) with their targets to enable recognition. Transfer of target cell-derived Ags together with proximal molecules onto the effector cell appears also to occur through synapses. Little is known about the molecular basis of this transfer, but it is assumed to result from Ag receptor internalization. Because human gamma delta T cells recognize soluble nonpeptidic phosphoantigens as well as tumor cells such as Daudi, it is unknown whether they establish IS with, and extract molecules from, target cells. Using flow cytometry and confocal microscopy, we show in this work that Ag-stimulated human V gamma 9/V delta 2 T cells conjugate to, and perform molecular transfer from, various tumor cell targets. The molecular transfer appears to be linked to IS establishment, evolves in a dose-dependent manner in the presence of either soluble or cellular Ag, and requires gamma delta TCR ligation, Src family kinase signaling, and participation of the actin cytoskeleton. Although CD45 exclusion characterized the IS performed by gamma delta T cells, no obvious capping of the gamma delta TCR was detected. The synaptic transfer mediated by gamma delta T cells involved target molecules unrelated to the cognate Ag and occurred independently of MHC class I expression by target cells. From these observations, we conclude that despite the particular features of gamma delta T cell activation, both synapse formation and molecular transfer of determinants belonging to target cell characterize gamma delta T cell recognition of Ags.     

Prion protein interaction with glycosaminoglycan occurs with the formation of oligomeric complexes stabilized by Cu(II) bridges

Several lines of evidence have shown glycosaminoglycans (GAGs) to be physiological ligands of the prion protein (PrP), but the molecular and regulatory aspects of the interaction remain unknown. Using full-length recombinant prion protein and low molecular mass heparin and heparan sulfate as glycosaminoglycans, we have found that the interaction occurs with the formation of oligomeric complexes. Within the protein-glycosaminoglycan complexes, PrP exhibited an enhanced fluorescence emission and a reduced solvent exposure. The pH and ionic strength-dependence of the interaction reveals His residues as the main binding sites at acid pH. A synthetic peptide consisting of four octarepeats is able to reproduce the His-dependent binding of the protein, thus demonstrating the role of the octarepeats in the GAG interaction. Alternatively, PrP can bind GAGs through His-bound Cu(II). These Cu(II) bridges promote a tighter interaction, as shown by the increased resistance to ionic strength, to protease action, and to pH-induced cation release. Inspection of other cations shows that Zn(II) but not Ni(II) shares the interaction trend. Taken together, our data suggest that the octarepeat region constitutes a novel GAG-binding sequence and that His-bound Cu(II) may act as a cofactor for intermolecular recognition reactions, allowing the formation of PrP-Cu(II)-glycosaminoglycan assemblies that may be crucial entities in the PrP metabolism.     

Mexican native trouts: a review of their history and current systematic and conservation status

While biologists have been aware of theexistence of native Mexican trouts for over acentury, they have received little study. Thefew early studies that did much more thanmention their existence began in the 1930s andcontinued into the early 1960s, focusingprimarily on distributional surveys andtaxonomic analyses. Starting in the 1980s theBaja California rainbow trout became thesubject of more detailed studies, but verylittle remains known of mainland trouts of theSierra Madre Occidental. We review earlierstudies and report on our own collections andobservations made between 1975 and 2000. Wepresent newly discovered historical evidencethat leads us to conclude that a lostcutthroat trout, a lineage not previously knownfrom Mexico, was collected more than a centuryago from headwaters of the Río Conchos (amajor tributary of the Rio Grande (= RíoBravo)), a basin not previously considered toharbor a native trout. We review the lastcentury of regional natural resource managementand discuss our own observations of trouthabitats. Impacts of logging, road building andovergrazing are widespread and expanding. Manystreams suffer from heavy erosion, siltationand contamination, and though long-termhydrologic data are generally not available,there is evidence of decreased discharge inmany streams. These problems appear related toregion-wide land management practices as wellas recent regional drought. Trout cultureoperations using exotic rainbow trout haverapidly proliferated throughout the region,threatening genetic introgression and/orcompetition with native forms and predation onthem. Knowledge of distribution, abundance,relationships and taxonomy, not to mentionecology and population biology, of nativetrouts of the Sierra Madre Occidental remainsinadequate. Vast areas of most mainlanddrainages are still unexplored by fishcollectors, and even rudimentary informationregarding basic biology, ecology and populationstructure of stocks remains lacking.Concentrated exploration, research andmanagement of this long overlooked andundervalued resource are all urgently needed.The history of natural resources exploitationthat placed so many native trouts of thewestern United States on threatened andendangered species lists is repeating itself inthe Sierra Madre Occidental. Without concertedaction and development of region-widesocio-economic solutions for current, largelynon-sustainable resource management practices,native Mexican trout gene pools will soon be ingrave danger of extinction.