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981.
Grieder C Dhillon BS Schipprack W Melchinger AE 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2012,124(6):971-980
Biofuels have gained importance recently and the use of maize biomass as substrate in biogas plants for production of methane
has increased tremendously in Germany. The objectives of our research were to (1) estimate variance components and heritability
for different traits relevant to biogas production in testcrosses (TCs) of maize, (2) study correlations among traits, and
(3) discuss strategies to breed maize as a substrate for biogas fermenters. We evaluated 570 TCs of 285 diverse dent maize
lines crossed with two flint single-cross testers in six environments. Data were recorded on agronomic and quality traits,
including dry matter yield (DMY), methane fermentation yield (MFY), and methane yield (MY), the product of DMY and MFY, as
the main target trait. Estimates of variance components showed general combining ability (GCA) to be the major source of variation.
Estimates of heritability exceeded 0.67 for all traits and were even much greater in most instances. Methane yield was perfectly
correlated with DMY but not with MFY, indicating that variation in MY is primarily determined by DMY. Further, DMY had a larger
heritability and coefficient of genetic variation than MFY. Hence, for improving MY, selection should primarily focus on DMY
rather than MFY. Further, maize breeding for biogas production may diverge from that for forage production because in the
former case, quality traits seem to be of much lower importance. 相似文献
982.
Grieder C Dhillon BS Schipprack W Melchinger AE 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2012,124(6):981-988
Breeding maize for use as a biogas substrate (biogas maize) has recently gained considerable importance. To optimize hybrid
breeding programs, information about line per se performance (LP) of inbreds and its relation to their general combining ability
(GCA) is required. The objectives of our research were to (1) estimate variance components and heritability of LP for agronomic
and quality traits relevant to biogas production, (2) study correlations among traits as well as between LP and GCA, and (3)
discuss implications for breeding of biogas maize. We evaluated 285 diverse dent maize inbred lines in six environments. Data
were recorded on agronomic and quality traits, including dry matter yield (DMY), methane fermentation yield (MFY), and their
product, methane yield (MY), as the main target trait. In agreement with observations made for GCA in a companion study, variation
in MY was mainly determined by DMY. MFY, which showed moderate correlation with lignin but only weak correlation with starch,
revealed only low genotypic variation. Thus, our results favor selection of genotypes with high DMY and less focus on ear
proportion for biogas maize. Genotypic correlations between LP and GCA [r
g (LP, GCA)] were highest (≥0.94) for maturity traits (days to silking, dry matter concentration) and moderate (≥0.65) for
DMY and MY. Multistage selection is recommended. Selection for GCA of maturity traits, plant height, and to some extent also
quality traits and DMY on the level of LP looks promising. 相似文献
983.
Clostridium aminobutyricum ferments 4-aminobutyrate (γ-aminobutyrate, GABA) to ammonia, acetate and butyrate via 4-hydroxybutyrate that is activated
to the CoA-thioester catalyzed by 4-hydroxybutyrate CoA-transferase. Then, 4-hydroxybutyryl-CoA is dehydrated to crotonyl-CoA,
which disproportionates to butyryl-CoA and acetyl-CoA. Cocrystallization of the CoA-transferase with the alternate substrate
butyryl-CoA yielded crystals with non-covalently bound CoA and two water molecules at the active site. Most likely, butyryl-CoA
reacted with the active site Glu238 to CoA and the mixed anhydride, which slowly hydrolyzed during crystallization. The structure
of the CoA is similar but less stretched than that of the CoA-moiety of the covalent enzyme-CoA-thioester in 4-hydroxybutyrate
CoA-transferase from Shewanella oneidensis. In contrast to the structures of the apo-enzyme and enzyme-CoA-thioester, the structure described here has a closed conformation,
probably caused by a flip of the active site loop (residues 215–219). During turnover, the closed conformation may protect
the anhydride intermediate from hydrolysis and CoA from dissociation from the enzyme. Hence, one catalytic cycle changes conformation
of the enzyme four times: free enzyme—open conformation, CoA+ anhydride 1—closed, enzyme-CoA-thioester—open, CoA + anhydride-2—closed,
free enzyme—open. 相似文献
984.
985.
986.
Increased l-Arg (Arg) uptake to astrocytes and neurons is thought to contribute to enhanced nitric oxide (NO) synthesis and oxidative/nitrosative stress associated with hyperammonemia (HA). Recently we had shown that HA increases the expression in the brain of y(+)LAT2, an isoform of the y(+)L heteromeric transporter which promotes [(3)H]Arg efflux form brain cells in the presence of l-glutamine (Gln) (Zielińska et al., 2011). In this study, we demonstrate that a significant proportion of [(3)H]Arg uptake to cultured cortical astrocytes is likewise mediated by system y(+)L, in addition to the uptake showing characteristics of systems y(+), B(0+) and b(0+). However, stimulation of [(3)H]Arg uptake by treatment with 5mM ammonium chloride ("ammonia") for 48h could be solely ascribed to the y(+)L-mediated component of the uptake. Ammonia treatment increased the expression of the brain specific y(+)L isoform, y(+)LAT2, both at the mRNA and protein level, and silencing of the Slc7a6 gene coding for y(+)LAT2 protein specifically reduced the ammonia-induced [(3)H]Arg uptake. This study suggests an important role of y(+)LAT2 in the modulation of NO synthesis in the ammonia-exposed astrocytes. 相似文献
987.
988.
Correa SM Washburn LL Kahlon RS Musson MC Bouma GJ Eicher EM Albrecht KH 《PLoS genetics》2012,8(4):e1002569
Sex reversal can occur in XY humans with only a single functional WT1 or SF1 allele or a duplication of the chromosome region containing WNT4. In contrast, XY mice with only a single functional Wt1, Sf1, or Wnt4 allele, or mice that over-express Wnt4 from a transgene, reportedly are not sex-reversed. Because genetic background plays a critical role in testis differentiation, particularly in C57BL/6J (B6) mice, we tested the hypothesis that Wt1, Sf1, and Wnt4 are dosage sensitive in B6 XY mice. We found that reduced Wt1 or Sf1 dosage in B6 XY(B6) mice impaired testis differentiation, but no ovarian tissue developed. If, however, a Y(AKR) chromosome replaced the Y(B6) chromosome, these otherwise genetically identical B6 XY mice developed ovarian tissue. In contrast, reduced Wnt4 dosage increased the amount of testicular tissue present in Sf1+/- B6 XY(AKR), Wt1+/- B6 XY(AKR), B6 XY(POS), and B6 XY(AKR) fetuses. We propose that Wt1(B6) and Sf1(B6) are hypomorphic alleles of testis-determining pathway genes and that Wnt4(B6) is a hypermorphic allele of an ovary-determining pathway gene. The latter hypothesis is supported by the finding that expression of Wnt4 and four other genes in the ovary-determining pathway are elevated in normal B6 XX E12.5 ovaries. We propose that B6 mice are sensitive to XY sex reversal, at least in part, because they carry Wt1(B6) and/or Sf1(B6) alleles that compromise testis differentiation and a Wnt4(B6) allele that promotes ovary differentiation and thereby antagonizes testis differentiation. Addition of a "weak" Sry allele, such as the one on the Y(POS) chromosome, to the sensitized B6 background results in inappropriate development of ovarian tissue. We conclude that Wt1, Sf1, and Wnt4 are dosage-sensitive in mice, this dosage-sensitivity is genetic background-dependant, and the mouse strains described here are good models for the investigation of human dosage-sensitive XY sex reversal. 相似文献
989.
990.