Biochemical evidence of a translocation between 6 RL/7 RL chromosome arms in rye (Secale cereale L.). A genetic map of 6R chromosome

Summary The segregation of different isozymic loci was investigated in backcrosses and F₂s in rye. The leucin aminopeptidase-1 (Lap-1), Aconitase-1 (Aco-1), Esterase-6 (Est-6), Esterase-8 (Est-8), and Endopeptidase-1 (Ep-1) loci were linked. The Aco-1, Est-6, and Est-8 loci have been previously located on the 6RL chromosome arm. The Lap-1 locus has been located on the 6RS chromosome arm. The results favor the gene order: Lap-1... (centromere)... Aco-1... Est-8... Est-6... Ep-1. The isoelectric focusing separations of aqueous extracts from mature embryo tissue of wheat-rye addition and substitution lines involving the chromosomes of cereal rye Secale cereale L. confirmed the gene location of locus Ep-1 on the 6RL chromosome arm. Screening of wheat-rye addition lines involving the chromosomes of Secale montanum revealed that Ep-1 locus is not located on chromosome 6R of S. montanum. These results are the first biochemical evidence of the translocation between chromosome arms 6RL/7RL in the evolution of S. cereale from S. montanum.     

Degradation of benzene, toluene, and xylene isomers by a bacterial consortium obtained from rhizosphere soil of Cyperus sp. grown in a petroleum-contaminated area

Increasing contamination of soil and groundwater with benzene, toluene, and xylene (BTX) due to activities of the chemical and oil refinery industry has caused serious environmental damage. Efficient methods are required to isolate and degrade them. Microorganisms associated with rhizosphere soil are considered efficient agents to remediate hydrocarbon contamination. In this study, we obtained a stabilized bacterial consortium from the rhizosphere soil of Cyperus sp. grown in a petroleum-contaminated field in Southern Mexico. This consortium was able to completely degrade BTX in 14 days. Bacteria isolated from the consortium were identified by 16S rRNA gene sequence analysis as Ralstonia insidiosa, Cellulomonas hominis, Burkholderia kururiensis, and Serratia marcescens. The BTX-degradation capacity of the bacterial consortium was confirmed by the detection of genes pheA, todC1, and xylM, which encoded phenol hydroxylase, toluene 1,2-dioxygenase, and xylene monooxygenase, respectively. Our results demonstrate feasibility of BTX biodegradation by indigenous bacteria that might be used for soil remediation in Southern Mexico.     

Fractionation of Heavy Metals in Mine Tailings Amended with Composted Manure

This study evaluated the effect of composted cow manure (CCM) on the chemical fractionation and retention degree of heavy metals (HMs) in mine tailings from Zimapán, México. In a greenhouse experiment, mine tailings from three deposits were incubated for 3 months; experimental units were placed in a PVC container, where increasing doses of CCM were applied. HM pseudo-total concentrations, HM extractions with ethylenediaminetetraacetic acid (EDTA, 0.05 M), and a sequential chemical extraction (SCE) were carried out. The HM concentrations were determined by atomic absorption spectrophotometry. The pseudo-total concentrations of Pb, Cu, Cd, and Ni found were up to 1506, 206, 27, and 23 mg kg^?1, respectively; extractable Pb was up to 42%; 21% for Cu; 51% for Cd; and 16% of Ni of the pseudo-total concentrations of each metal. Treatment with 12% of CCM in mine tailing decreased EDTA-extractable HM concentrations, while the SCE revealed a decrease in exchangeable fraction and an increase in the organic fraction of HM. A positive correlation between CCM application and organic fractions of HMs was found, although the highest increasements were recorded in the organic fraction.     

Characterization of the atypical Ppz/Hal3 phosphatase system from the pathogenic fungus Cryptococcus neoformans

Ppz Ser/Thr protein phosphatases (PPases) are found only in fungi and have been proposed as potential antifungal targets. In Saccharomyces cerevisiae Ppz1 (ScPpz1) is involved in regulation of monovalent cation homeostasis. ScPpz1 is inhibited by two regulatory proteins, Hal3 and Vhs3, which have moonlighting properties, contributing to the formation of an unusual heterotrimeric PPC decarboxylase (PPCDC) complex crucial for CoA biosynthesis. Here we report the functional characterization of CnPpz1 (CNAG_03673) and two possible Hal3‐like proteins, CnHal3a (CNAG_00909) and CnHal3b (CNAG_07348) from the pathogenic fungus Cryptococcus neoformans. Deletion of CnPpz1 or CnHal3b led to phenotypes unrelated to those observed in the equivalent S. cerevisiae mutants, and the CnHal3b‐deficient strain was less virulent. CnPpz1 is a functional PPase and partially replaced endogenous ScPpz1. Both CnHal3a and CnHal3b interact with ScPpz1 and CnPpz1 in vitro but do not inhibit their phosphatase activity. Consistently, when expressed in S. cerevisiae, they poorly reproduced the Ppz1‐regulatory properties of ScHal3. In contrast, both proteins were functional monogenic PPCDCs. The CnHal3b isoform was crystallized and, for the first time, the 3D‐structure of a fungal PPCDC elucidated. Therefore, our work provides the foundations for understanding the regulation and functional role of the Ppz1‐Hal3 system in this important pathogenic fungus.     

Radial mass density, charge, and epitope distribution in the Cryptococcus neoformans capsule

Exposure of Cryptococcus neoformans cells to gamma radiation results in a gradual release of capsular polysaccharide, in a dose-dependent manner. This method allows the systematic exploration of different capsular regions. Using this methodology, capsule density was determined to change according to the radial distribution of glucuronoxylomannan and total polysaccharide, becoming denser at the inner regions of the capsule. Scanning electron microscopy of cells following gamma radiation treatment confirmed this finding. The zeta potential of the capsule also increased as the capsule size decreased. However, neither charge nor density differences were correlated with any change in sugar composition (xylose, mannose, and glucuronic acid) in the different capsular regions, since the proportions of these sugars remained constant throughout the capsule. Analysis of the capsular antigenic properties by monoclonal antibody binding and Scatchard analysis revealed fluctuations in the binding affinity within the capsule but not in the number of antibody binding sites, suggesting that the spatial organization of high- and low-affinity epitopes within the capsule changed according to radial position. Finally, evidence is presented that the structure of the capsule changes with capsule age, since the capsule of older cells became more resistant to gamma radiation-induced ablation. In summary, the capsule of C. neoformans is heterogeneous in its spatial distribution and changes with age. Furthermore, our results suggest several mechanisms by which the capsule may protect the fungal cell against exogenous environmental factors.     

Solar radiation and functional traits explain the decline of forest primary productivity along a tropical elevation gradient

One of the major challenges in ecology is to understand how ecosystems respond to changes in environmental conditions, and how taxonomic and functional diversity mediate these changes. In this study, we use a trait‐spectra and individual‐based model, to analyse variation in forest primary productivity along a 3.3 km elevation gradient in the Amazon‐Andes. The model accurately predicted the magnitude and trends in forest productivity with elevation, with solar radiation and plant functional traits (leaf dry mass per area, leaf nitrogen and phosphorus concentration, and wood density) collectively accounting for productivity variation. Remarkably, explicit representation of temperature variation with elevation was not required to achieve accurate predictions of forest productivity, as trait variation driven by species turnover appears to capture the effect of temperature. Our semi‐mechanistic model suggests that spatial variation in traits can potentially be used to estimate spatial variation in productivity at the landscape scale.     

Blood biochemical polymorphisms as markers for genetic characteristics of wild Spanish and domestic rabbits

Seventeen blood proteins were studied in a sample of 412 Spanish wild rabbits and in 598 domestic rabbits belonging to various breeds. The wild rabbit populations showed a high level of genetic polymorphism. Six loci were monomorphic, while the remaining ten loci were segregating for at least two alleles. Two of the loci that were polymorphic in the wild rabbits were monomorphic in the domestic ones. Wright's inbreeding coefficient in the total Spanish wild rabbit population was F=5.66, indicating subdivision of the total population. Inbreeding coefficients, estimated by Kidd et al.'s method (Anim. Blood Grps, Biochem. Genet. 11: 21–38), differed significantly from zero, being 15.62%, in wild rabbits and 6–12% in domestic breeds, indicating consanguinity.Genetic distances between wild rabbit populations showed that factors other than geographic distance (e.g., bottlenecks, barriers such as rivers, mountains, etc.) may explain the result that a northern population forms a cluster with two central populations whereas the northeastern populations form a different cluster with another central population. Populations of the first cluster are more closely related to the captive populations than others.There are three population clusters of domestic rabbits, namely (1) New Zealand White and a hybrid combination; (2) Spanish Common, Butterfly, Burgundy, and Californian; and (3) Spanish Giant.