Hg concentrations in fish from coastal waters of California and Western North America.

The State of California conducted an extensive and systematic survey of mercury (Hg) in fish from the California coast in 2009 and 2010. The California survey sampled 3483 fish representing 46 species at 68 locations, and demonstrated that methylHg in fish presents a widespread exposure risk to fish consumers. Most of the locations sampled (37 of 68) had a species with an average concentration above 0.3µg/gwet weight (ww), and 10 locations an average above 1.0µg/gww. The recent and robust dataset from California provided a basis for a broader examination of spatial and temporal patterns in fish Hg in coastal waters of Western North America. There is a striking lack of data in publicly accessible databases on Hg and other contaminants in coastal fish. An assessment of the raw data from these databases suggested the presence of relatively high concentrations along the California coast and in Puget Sound, and relatively low concentrations along the coasts of Alaska and Oregon, and the outer coast of Washington. The dataset suggests that Hg concentrations of public health concern can be observed at any location on the coast of Western North America where long-lived predator species are sampled. Output from a linear mixed-effects model resembled the spatial pattern observed for the raw data and suggested, based on the limited dataset, a lack of trend in fish Hg over the nearly 30-year period covered by the dataset. Expanded and continued monitoring, accompanied by rigorous data management procedures, would be of great value in characterizing methylHg exposure, and tracking changes in contamination of coastal fish in response to possible increases in atmospheric Hg emissions in Asia, climate change, and terrestrial Hg control efforts in coastal watersheds.

Spatial trends and impairment assessment of mercury in sport fish in the Sacramento-San Joaquin Delta watershed.

A three-year study was conducted to examine mercury in sport fish from the Sacramento-San Joaquin Delta. More than 4000 fish from 31 species were collected and analyzed for total mercury in individual muscle filets. Largemouth bass and striped bass were the most contaminated, averaging 0.40 microg/g, while redear sunfish, bluegill and rainbow trout exhibited the lowest (<0.15 microg/g) concentrations. Spatial variation in mercury was evaluated with an analysis of covariance model, which accounted for variability due to fish size and regional hydrology. Significant regional differences in mercury were apparent in size-standardized largemouth bass, with concentrations on the Cosumnes and Mokelumne rivers significantly higher than the central and western Delta. Significant prey-predator mercury correlations were also apparent, which may explain a significant proportion of the spatial variation in the watershed.

Molecular and ultrastructural analysis of a nonchromosomal variegated mutant. Tomato mitochondrial mutants that cause abnormal leaf development.

Mutants were recovered in a population of cybrids formed following protoplast fusion between tomato (Lycopersicon esculentum Mill.) cv UC82 and Lycopersicon pennellii Corr. The cybrids were identified as individuals with recombinant cytoplasmic genomes but only tomato nuclear genomes. The mutants were identified based on two features, a variegated sectoring of light and dark green regions on their leaves, stems, and fruit, and reduced growth in the field. The mutants produced 50% of the shoot fresh weight and 20% of the fruit fresh weight of the parental type, UC82. The variegated sectoring was maternally inherited. The chloroplast genome in the mutants was indistinguishable from the chloroplast genome in UC82, when distribution of restriction endonuclease sites was used as an assay. The mitochondrial genome in the mutants, however, was recombinant, containing genes from UC82 and L. pennellii. Light microscopic analysis of the leaves of the mutants demonstrated an absence of the palisade layer in the variegated sectors. Electron microscopic analysis of these same regions demonstrated an absence of normal inner membranes in the mitochondria of these cells.

Non-random inheritance of organellar genomes in symmetric and asymmetric somatic hybrids between Lycopersicon esculentum and L. pennellii.

The organization of the mitochondrial genome and the genotype of the chloroplast genome was characterized using restriction fragment length polymorphisms in a population (82 individuals) of symmetric and asymmetric somatic hybrids of tomato. The protoplast fusion products were regenerated following the fusion of leaf mesophyll protoplasts of Lycopersicon esculentum (tomato cv 'UC82') with suspension cell protoplasts of L. pennellii that had been irradiated with 5, 10, 15, 25, 50, or 100 kRads from a gamma source. The chloroplast genome in the somatic hybrids showed a random pattern of inheritance, i.e., either parental genome was present in equal numbers of regenerants, while in asymmetric somatic hybrids, the chloroplast genotype reflected the predominant nuclear genotype, i.e., tomato. The mitochondrial genome in the symmetric somatic hybrids showed a non-random pattern of inheritance, i.e., predominantly from the L. pennellii parent; asymmetric somatic hybrids had more tomato-specific mitochondrial sequences than symmetric somatic hybrids. The non-random inheritance of the chloroplast and mitochondrial DNA in these tomato protoplast fusion products appears to be influenced by the nuclear background of the regenerant.

Molecular analysis of the nuclear organellar genotype of somatic hybrid plants between tomato (Lycopersicon esculentum) and Lycopersicon chilense.

Somatic hybrid plants were recovered following fusion of leaf mesophyll protoplasts isolated from tomato (Lycopersicon esculentum) cultivar UC82 with protoplasts isolated from suspension cultured cells of L. chilense, LA 1959. Iodoacetate was used to select against the growth of unfused tomato protoplasts. Two somatic hybrids were recovered in a population of 16 regenerants. No tomato regenerants were recovered; all of the non-hybrid regenerants were L. chilense. The L. chilense protoplast regenerants were tetraploid. The hybrid nature of the plants was verified using species-specific restriction fragment length polymorphisms for the nuclear, chloroplast and mitochondrial genomes. The somatic hybrids had inherited the chloroplast DNA of the tomato parent, and portions of the mitochondrial DNA of the L. chilense parent. The somatic hybrids formed flowers and developed seedless fruit.

Tomato cybrids with mitochondrial DNA from Lycopersicon pennelli.

Cybrids have been regenerated following protoplast fusion of iodoacetamide-treated leaf mesophyll cells of Lycopersion esculentum cv UC82 and gamma-irradiated cell suspensions of L. pennellii, LA716. The cybrids were recovered in the regenerant population at a frequency of 19%, no selection pressure was applied for the persistence of the donor cytoplasm. The nuclear genotype of ten cybrids was characterized extensively using isozyme markers, cDNA-based restriction fragment length polymorphisms (RFLPs), and the morphology of the plants. No nuclear genetic information from L. pennellii was detected in the cybrids. The organellar genotype of the cybrids was determined using cloned probes and species-specific RFLPs. All the cybrids had inherited the tomato chloroplast genome and had varying amounts of L. pennellii mitochondrial DNA. The cybrids all had a diploid chromosome number of 24, produced pollen, and set seed.

Comparison of the organization of the mitochondrial genome in tomato somatic hybrids and cybrids.

The organization of the mitochondrial genome in somatic hybrids and cybrids regenerated following fusion of protoplasts from cultivated tomato, Lycopersicon esculentum, and the wild species, L. Pennellii, was compared to assess the role of the nuclear genotype on the inheritance of organellar genomes. No organellar-encoded traits were required for the recorvery of either somatic hybrids or cybrids. The organization of the mitochondrial genome was characterized using Southern hybridization of restriction digestions of total DNA isolated from ten cybrids and ten somatic hybrids. A bank of cosmid clones carrying tomato mitochondrial DNA was used as probes, as well as a putative repeated sequence from L. pennellii mitchondrial DNA. The seven cosmids used to characterize the mitochondrial genomes are predicted to encompass at least 60% of the genome. The frequency of nonparental organizations of the mitochondrial genome was highest with a probe derived from a putative repeat element from the L. pennellii mitochondrial DNA. There was no difference in the average frequency of rearranged mitochondrial sequences in somatic hybrids (12%) versus cybrids (10%), although there were individual cybrids with a very high frequency of novel fragments (30%). The frequency of tomato-specific mtDNA sequences was higher in cybrids (25%) versus somatic hybrids (12%), suggesting a nuclear-cytoplasmic interaction on the inheritance of tomato mitochondrial sequences.