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51.
52.
HANS RYBERG LENNART AXELSSON KARL-OLOF WIDELL HEMMING I. VIRGIN 《Physiologia plantarum》1980,49(4):431-436
Abstract When dark grown leaves of wheat (Triticum aesivum L.) were given a brief irradiation, there was an immediate onset of chlorophyll (Chl) b synthesis in the dark. This synthesis led to a rather slow accumulation of Chl b, which ceased when the Chl b/Chl a ratio had reached a value of about 0.1. The Chl b synthesis occurred also when the seedlings were treated with the herbicide SAN 9789. Leaves grown under different intensities of red light accumulated Chl b and Chl a, resulting in a ratio Chl b/Chl a which depended on the light intensity. If the light intensity was low, Chl a accumulated to a level about ten times the level of PChlide of the dark grown leaves. This occurred without any increase in the Chl b/Chl a ratio. There was no difference between SAN 9789-treated seedlings and water controls in this respect. Above a certain threshold of irradiance, the Chl b/Chl a ratio in the control leaves increased rapidly with the irradiation intensity. The increase in Chl b/Chl a ratio coincided with formation of grana in the plastids. This increase was not found and grana formation was completely absent in the seedlings treated with SAN 9789. The possibility of two different stages in the Chl b synthesis is discussed. 相似文献
53.
Tinoush Moulaei Olga Stuchlik Matthew Reed Weirong Yuan Jan Pohl Wuyuan Lu Lauren Haugh-Krumpe Barry R O'Keefe Alexander Wlodawer 《Protein science : a publication of the Protein Society》2010,19(9):1649-1661
The antiviral lectin scytovirin (SVN) contains a total of five disulfide bonds in two structurally similar domains. Previous reports provided contradictory results on the disulfide pairing in each individual domain, and we have now re‐examined the disulfide topology. N‐terminal sequencing and mass spectrometry were used to analyze proteolytic fragments of native SVN obtained at acidic pH, yielding the assignment as Cys7–Cys55, Cys20–Cys32, Cys26–Cys38, Cys68–Cys80, and Cys74–Cys86. We also analyzed the N‐terminal domain of SVN (SD1, residues 1–48) prepared by expression/oxidative folding of the recombinant protein and by chemical synthesis. The disulfide pairing in the chemically synthesized SD1 was forced into predetermined topologies: SD1A (Cys20–Cys26, Cys32–Cys38) or SD1B (Cys20–Cys32, Cys26–Cys38). The topology of native SVN was found to be in agreement with the SD1B and the one determined for the recombinant SD1 domain. Although the two synthetic forms of SD1 were distinct when subjected to chromatography, their antiviral properties were indistinguishable, having low nM activity against HIV. Tryptic fragments, the “cystine clusters” [Cys20–Cys32/Cys26–Cys38; SD1] and [Cys68–Cys80/Cys74–C‐86; SD2], were found to undergo rapid disulfide interchange at pH 8. This interchange resulted in accumulation of artifactual fragments in alkaline pH digests that are structurally unrelated to the original topology, providing a rational explanation for the differences between the topology reported herein and the one reported earlier (Bokesh et al., Biochemistry 2003;42:2578–2584). Our observations emphasize the fact that proteins such as SVN, with disulfide bonds in close proximity, require considerable precautions when being fragmented for the purpose of disulfide assignment. 相似文献
54.
Monoclonal antibodies of predetermined specificity were prepared by immunization with a free (i.e., without coupling to any protein carrier) synthetic peptide representing region 145–151 of sperm whale myoglobin (SpMb) and their cross-reactions with eight Mb variants were determined. Five Mbs—bottle-nose dolphin myoglobin (BdMb), pacific common dolphin myoglobin (PdMb), horse myoglobin (HsMb), dog myoglobin (DgMb), and badger myoglobin (BgMb)—have an identical sequence in that region. Nevertheless, these Mbs exhibited very different cross-reactivities. BdMb and PdMb exhibited cross-activities which were comparable to that of the reference antigen, SpMb; while the reactivity of HsMb was remarkedly decreased, DgMb and BgMb showed almost no cross-reactions with these mAbs. Since the region 145–151 has an identical sequence in all the five Mbs, it is concluded that the differences in their antigenic reactivities with anti-region 145–151 mAbs are due to the effects of amino acid substitutions outside the region 145–151. Another pair of myoglobins, echidna myoglobin (EdMb) and chicken myoglobin (ChMb), have the same sequence in that region, but reacted very differently with anti-region 145–151 mAbs. The reactivity and affinity of EdMb were substantially decreased while those of ChMb were almost completely absent, relative to SpMb. It is concluded, contrary to popular assumptions, that when an amino acid substitution influences the binding of a protein variant to a mAb, it is not necessary for that substitution to be an actual contact residue (i.e., a residue within the antigenic site where the mAb binds). Such effects, which are often very drastic, could be due to indirect influences of the substitution on the chemical and binding properties of the site residues. Furthermore, residues which had been postulated, on the basis of these assumptions, to constitute discontinuous antigenic sites in SpMb, were found [from the present studies and those recently reported with mAbs against the other four antigenic site of Mb (regions 15–22, 56–62, 94–100, and 113–120 of SpMb)] to merely be exerting indirect effects on the known five antigenic sites of Mb. The effects of substitutions, which can happen even in the absence of conformational changes, are determined by many factors, such as the chemical nature of the substitution, its environment, its distance from the site, and the nature of the site residue(s) being affected. 相似文献
55.
M. Lorenzo M. L. Pinedo M. A. Equiza P. V. Fernndez M. Ciancia D. G. Ganem J. A. Tognetti 《Plant biology (Stuttgart, Germany)》2019,21(Z1):84-94
- Temperate grasses, such as wheat, become compact plants with small thick leaves after exposure to low temperature. These responses are associated with cold hardiness, but their underlying mechanisms remain largely unknown. Here we analyse the effects of low temperature on leaf morpho‐anatomical structure, cell wall composition and activity of extracellular peroxidases, which play key roles in cell elongation and cell wall thickening, in two wheat cultivars with contrasting cold‐hardening ability.
- A combined microscopy and biochemical approach was applied to study actively growing leaves of winter (ProINTA‐Pincén) and spring (Buck‐Patacón) wheat developed under constant warm (25 °C) or cool (5 °C) temperature.
- Cold‐grown plants had shorter leaves but longer inter‐stomatal epidermal cells than warm‐grown plants. They had thicker walls in metaxylem vessels and mestome sheath cells, paralleled with accumulation of wall components, predominantly hemicellulose. These effects were more pronounced in the winter cultivar (Pincén). Cold also induced a sharp decrease in apoplastic peroxidase activity within the leaf elongating zone of Pincén, and a three‐fold increase in the distal mature zone of the leaf. This was consistent with the enhanced cell length and thicker cell walls in this cultivar at 5 °C.
- The different response to low temperature of apoplastic peroxidase activity and hemicellulose between leaf zones and cultivar types suggests they might play a central role in the development of cold‐induced compact morphology and cold hardening. New insights are presented on the potential temperature‐driven role of peroxidases and hemicellulose in cell wall dynamics of grasses.
56.
57.
Jiacheng Hu Shaoya Li Zhaolei Li Huiyuan Li Weibin Song Haiming Zhao Jinsheng Lai Lanqin Xia Dawei Li Yongliang Zhang 《Molecular Plant Pathology》2019,20(10):1463-1474
Plant RNA virus-based guide RNA (gRNA) delivery has substantial advantages compared to that of the conventional constitutive promoter-driven expression due to the rapid and robust amplification of gRNAs during virus replication and movement. To date, virus-induced genome editing tools have not been developed for wheat and maize. In this study, we engineered a barley stripe mosaic virus (BSMV)-based gRNA delivery system for clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-mediated targeted mutagenesis in wheat and maize. BSMV-based delivery of single gRNAs for targeted mutagenesis was first validated in Nicotiana benthamiana. To extend this work, we transformed wheat and maize with the Cas9 nuclease gene and selected the wheat TaGASR7 and maize ZmTMS5 genes as targets to assess the feasibility and efficiency of BSMV-mediated mutagenesis. Positive targeted mutagenesis of the TaGASR7 and ZmTMS5 genes was achieved for wheat and maize with efficiencies of up to 78% and 48%. Our results provide a useful tool for fast and efficient delivery of gRNAs into economically important crops. 相似文献
58.
Species interactions change when the external conditions change. How these changes affect microbial community properties is an open question. We address this question using a two‐species consortium in which species interactions change from exploitation to competition depending on the carbon source provided. We built a mathematical model and calibrated it using single‐species growth measurements. This model predicted that low frequencies of change between carbon sources lead to species loss, while intermediate and high frequencies of change maintained both species. We experimentally confirmed these predictions by growing co‐cultures in fluctuating environments. These findings complement more established concepts of a diversity peak at intermediate disturbance frequencies. They also provide a mechanistic understanding for how the dynamics at the community level emerges from single‐species behaviours and interspecific interactions. Our findings suggest that changes in species interactions can profoundly impact the ecological dynamics and properties of microbial systems. 相似文献
59.
Gemma Molero Ryan Joynson Francisco J. Pinera‐Chavez Laura‐Jayne Gardiner Carolina Rivera‐Amado Anthony Hall Matthew P. Reynolds 《Plant biotechnology journal》2019,17(7):1276-1288
One of the major challenges for plant scientists is increasing wheat (Triticum aestivum) yield potential (YP). A significant bottleneck for increasing YP is achieving increased biomass through optimization of radiation use efficiency (RUE) along the crop cycle. Exotic material such as landraces and synthetic wheat has been incorporated into breeding programmes in an attempt to alleviate this; however, their contribution to YP is still unclear. To understand the genetic basis of biomass accumulation and RUE, we applied genome‐wide association study (GWAS) to a panel of 150 elite spring wheat genotypes including many landrace and synthetically derived lines. The panel was evaluated for 31 traits over 2 years under optimal growing conditions and genotyped using the 35K wheat breeders array. Marker‐trait association identified 94 SNPs significantly associated with yield, agronomic and phenology‐related traits along with RUE and final biomass (BM_PM) at various growth stages that explained 7%–17% of phenotypic variation. Common SNP markers were identified for grain yield, BM_PM and RUE on chromosomes 5A and 7A. Additionally, landrace and synthetic derivative lines showed higher thousand grain weight (TGW), BM_PM and RUE but lower grain number (GM2) and harvest index (HI). Our work demonstrates the use of exotic material as a valuable resource to increase YP. It also provides markers for use in marker‐assisted breeding to systematically increase BM_PM, RUE and TGW and avoid the TGW/GM2 and BM_PM/HI trade‐off. Thus, achieving greater genetic gains in elite germplasm while also highlighting genomic regions and candidate genes for further study. 相似文献
60.
A large nested association mapping population for breeding and quantitative trait locus mapping in Ethiopian durum wheat 总被引:2,自引:0,他引:2
Yosef G. Kidane Cherinet A. Gesesse Bogale N. Hailemariam Ermias A. Desta Dejene K. Mengistu Carlo Fadda Mario Enrico P Matteo Dell'Acqua 《Plant biotechnology journal》2019,17(7):1380-1393
The Ethiopian plateau hosts thousands of durum wheat (Triticum turgidum subsp. durum) farmer varieties (FV) with high adaptability and breeding potential. To harness their unique allelic diversity, we produced a large nested association mapping (NAM) population intercrossing fifty Ethiopian FVs with an international elite durum wheat variety (Asassa). The Ethiopian NAM population (EtNAM) is composed of fifty interconnected bi‐parental families, totalling 6280 recombinant inbred lines (RILs) that represent both a powerful quantitative trait loci (QTL) mapping tool, and a large pre‐breeding panel. Here, we discuss the molecular and phenotypic diversity of the EtNAM founder lines, then we use an array featuring 13 000 single nucleotide polymorphisms (SNPs) to characterize a subset of 1200 EtNAM RILs from 12 families. Finally, we test the usefulness of the population by mapping phenology traits and plant height using a genome wide association (GWA) approach. EtNAM RILs showed high allelic variation and a genetic makeup combining genetic diversity from Ethiopian FVs with the international durum wheat allele pool. EtNAM SNP data were projected on the fully sequenced AB genome of wild emmer wheat, and were used to estimate pairwise linkage disequilibrium (LD) measures that reported an LD decay distance of 7.4 Mb on average, and balanced founder contributions across EtNAM families. GWA analyses identified 11 genomic loci individually affecting up to 3 days in flowering time and more than 1.6 cm in height. We argue that the EtNAM is a powerful tool to support the production of new durum wheat varieties targeting local and global agriculture. 相似文献