Elevated CO(2) and temperature alter net ecosystem C exchange in a young Douglas fir mesocosm experiment

We investigated the effects of elevated CO(2) (EC) [ambient CO(2) (AC) + 190 ppm] and elevated temperature (ET) [ambient temperature (AT) + 3.6 degrees C] on net ecosystem exchange (NEE) of seedling Douglas fir (Pseudotsuga menziesii) mesocosms. As the study utilized seedlings in reconstructed soil-litter-plant systems, we anticipated greater C losses through ecosystem respiration (R(e)) than gains through gross photosynthesis (GPP), i.e. negative NEE. We hypothesized that: (1) EC would increase GPP more than R(e), resulting in NEE being less negative; and (2) ET would increase R(e) more than GPP, resulting in NEE being more negative. We also evaluated effects of CO(2) and temperature on light inhibition of dark respiration. Consistent with our hypothesis, NEE was a smaller C source in EC, not because EC increased photosynthesis but rather because of decreased respiration resulting in less C loss. Consistent with our hypothesis, NEE was more negative in ET because R(e) increased more than GPP. The light level that inhibited respiration varied seasonally with little difference among CO(2) and temperature treatments. In contrast, the degree of light inhibition of respiration was greater in AC than EC. In our system, respiration was the primary control on NEE, as EC and ET caused greater changes in respiration than photosynthesis.     

DNA adduct formation in human hepatoma cells treated with 3-nitrobenzanthrone: analysis by the (32)P-postlabeling method

3-Nitrobenzanthrone (3-nitro-7H-benz[d,e]anthracen-7-one, 3-NBA) is a powerful mutagen and a suspected human carcinogen existing in diesel exhaust and airborne particulates. Recently, one of the major presumed metabolites of 3-NBA, 3-aminobenzanthrone (3-ABA), was detected in human urine samples. Here we analyzed DNA adducts formed in 3-NBA-exposed human hepatoma HepG2 cells by a (32)P-postlabeling/thin layer chromatography (TLC) method and a (32)P-postlabeling/polyacrylamide gel electrophoresis (PAGE) method. With HepG2 cells exposed to 3-NBA (0.36-36.4 microM) for 3h, we obtained three spots or bands corresponding to adducted nucleotides. Two were assigned as 2-(2'-deoxyadenosin-N(6)-yl)-3-aminobenzanthrone-3'-phosphate (dA3'p-N(6)-C2-ABA) and 2-(2'-deoxyguanosin-N(2)-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-N(2)-C2-ABA), with identical mobilities to those of synthetic standards on PAGE analysis. The chemical structure of the substance corresponding to the other spot or band could not be identified. Quantitative analyses revealed that the major adduct was dA3'p-N(6)-C2-ABA and its relative adduct labeling (RAL) value at 36.4 microM of 3-NBA was 200.8+/-86.1/10(8)nucleotide.     

Mapping QTLs contributing to <Emphasis Type="Italic">Ustilago maydis</Emphasis> resistance in specific plant tissues of maize

Quantitative trait loci (QTL) contributing to the frequency and severity of Ustilago maydis infection in the leaf, ear, stalk, and tassel of maize plants were mapped using an A188 × CMV3 and W23 × CMV3 recombinant inbred (RI) populations. QTLs mapped to genetic bins 2.04 and 9.04–9.05 of the maize genome contributed strongly (R ² = 18–28%) to variation in the frequency and severity of U. maydis infection over the entire plant in both populations and within the majority of environments. QTLs mapped to bins 3.05, 3.08, and 8.00 in the A188 × CMV3 population and bin 4.05 in both populations significantly contributed to the frequency or severity of infection in only the tassel tissue. QTLs mapped to bin 1.07 in the A188 × CMV3 population and bin 7.00 in the W23 × CMV3 population contributed to U. maydis resistance in only the ear tissue. Interestingly, the CMV3 allele of the QTL mapped to bin 1.10 in the A188 × CMV3 population significantly contributed to U. maydis susceptibility in the ear and stalk but significantly increased resistance in the tassel tissue. Digenic epistatic interactions between the QTL mapped to bin 5.08 and four distinct QTLs significantly contributed to the frequency and severity of infection over the entire plant and within the tassel tissue of the A188 × CMV3 population. Several QTLs detected in this study mapped to regions of the maize genome containing previously mapped U. maydis resistance QTLs and genes involved in plant disease resistance. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Adding value to cocoa (Theobroma cacao L.) germplasm information with domestication history and admixture mapping

A sound understanding of crop history can provide the basis for deriving novel genetic information through admixture mapping. We confirmed this, by using characterization data from an international collection of cocoa, collected 25 years ago, and from a contemporary plantation. We focus on the trees derived from three centuries of admixture between Meso-American Criollo and South American Forastero genomes. In both cacao sets of individuals, linkage disequilibrium extended over long genetic distances along chromosome regions, as expected in populations derived from recent admixture. Based on loose genome scans, genomic regions involved in useful traits were identified. Fifteen genomic regions involved in seed and fruit weight variation were highlighted. They correspond to ten previously identified QTLs and five novel ones. Admixture mapping can help to add value to genetic resources and thus, help to encourage investment in their conservation. Maria Marcano and Tatiana Pugh contributed equally to this work.     

The 'human revolution' in lowland tropical Southeast Asia: the antiquity and behavior of anatomically modern humans at Niah Cave (Sarawak, Borneo)

Recent research in Europe, Africa, and Southeast Asia suggests that we can no longer assume a direct and exclusive link between anatomically modern humans and behavioral modernity (the 'human revolution'), and assume that the presence of either one implies the presence of the other: discussions of the emergence of cultural complexity have to proceed with greater scrutiny of the evidence on a site-by-site basis to establish secure associations between the archaeology present there and the hominins who created it. This paper presents one such case study: Niah Cave in Sarawak on the island of Borneo, famous for the discovery in 1958 in the West Mouth of the Great Cave of a modern human skull, the 'Deep Skull,' controversially associated with radiocarbon dates of ca. 40,000 years before the present. A new chronostratigraphy has been developed through a re-investigation of the lithostratigraphy left by the earlier excavations, AMS-dating using three different comparative pre-treatments including ABOX of charcoal, and U-series using the Diffusion-Absorption model applied to fragments of bones from the Deep Skull itself. Stratigraphic reasons for earlier uncertainties about the antiquity of the skull are examined, and it is shown not to be an 'intrusive' artifact. It was probably excavated from fluvial-pond-desiccation deposits that accumulated episodically in a shallow basin immediately behind the cave entrance lip, in a climate that ranged from times of comparative aridity with complete desiccation, to episodes of greater surface wetness, changes attributed to regional climatic fluctuations. Vegetation outside the cave varied significantly over time, including wet lowland forest, montane forest, savannah, and grassland. The new dates and the lithostratigraphy relate the Deep Skull to evidence of episodes of human activity that range in date from ca. 46,000 to ca. 34,000 years ago. Initial investigations of sediment scorching, pollen, palynomorphs, phytoliths, plant macrofossils, and starch grains recovered from existing exposures, and of vertebrates from the current and the earlier excavations, suggest that human foraging during these times was marked by habitat-tailored hunting technologies, the collection and processing of toxic plants for consumption, and, perhaps, the use of fire at some forest-edges. The Niah evidence demonstrates the sophisticated nature of the subsistence behavior developed by modern humans to exploit the tropical environments that they encountered in Southeast Asia, including rainforest.