QTL analysis for grain protein content using SSR markers and validation studies using NILs in bread wheat

QTL interval mapping for grain protein content (GPC) in bread wheat was conducted for the first time, using a framework map based on a mapping population, which was available in the form of 100 recombinant inbred lines (RILs). The data on GPC for QTL mapping was recorded by growing the RILs in five different environments representing three wheat growing locations from Northern India; one of these locations was repeated for 3 years. Distribution of GPC values followed normal distributions in all the environments, which could be explained by significant g x e interactions observed through analyses of variances, which also gave significant effects due to genotypes and environments. Thirteen (13) QTLs were identified in individual environments following three methods (single-marker analysis or SMA, simple interval mapping or SIM and composite interval mapping or CIM) and using LOD scores that ranged from 2.5 to 6.5. Threshold LOD scores (ranging from 3.05 to 3.57), worked out and used in each case, however, detected only seven of the above 13 QTLs. Only four (QGpc.ccsu-2B.1; QGpc.ccsu-2D.1; QGpc.ccsu-3D.1 and QGpc.ccsu-7A.1) of these QTLs were identified either in more than one location or following one more method other than CIM; another QTL (QGpc.ccsu-3D.2), which was identified using means for all the environments, was also considered to be important. These five QTLs have been recommended for marker-assisted selection (MAS). The QTLs identified as above were also validated using ten NILs derived from three crosses. Five of the ten NILs possessed 38 introgressed segments from 16 chromosomes and carried 42 of the 173 markers that were mapped. All the seven QTLs were associated with one or more of the markers carried by the above introgressed segments, thus validating the corresponding markers. More markers associated with many more QTLs to be identified should become available in the future by effective MAS for GPC improvement.     

The evolution of population stability as a by-product of life-history evolution

Proposed mechanisms for the evolution of population stability include group selection through longterm persistence, individual selection acting directly on stability determining the demographic parameters, and the evolution of stability as a by-product of life-history evolution. None of these hypotheses currently has clear empirical support. Using two sets of Drosophila melanogaster populations, we provide experimental evidence of stability evolving as a correlated response to selection on traits not directly related to demography. Four populations (FEJs) were selected for faster development and early reproduction for 125 generations, and the other four (JBs) were ancestral controls. All FEJ and JB populations have been maintained on discrete generations at moderate density, thus eliminating differential selection on stability determining demographic parameters. We derived eight small populations from each FEJ and JB population, and subjected four small populations each to either stabilizing or destabilizing food regimes. Census data on these 64 small populations over 20 generations clearly showed that the FEJ populations have significantly less temporal fluctuations in their numbers in both food regimes compared to their controls. This greater stability of the FEJ populations is probably a by-product of the evolution of reduced fecundity and pre-adult survivorship, as a correlated response to selection for rapid development.     

Targeted cybridization in citrus: transfer of Satsuma cytoplasm to seedy cultivars for potential seedlessness

CMS (cytoplasmic male sterility) can be controlled by the mitochondrion genome in higher plants, including Satsuma mandarin. Somatic fusion experiments in citrus combining embryogenic callus protoplasts of one parent with leaf protoplasts of a second parent often produce cybrid plants of the leaf parent, a phenomenon occurring most often with interspecific fusion combinations. In an attempt to practically exploit this cybridization phenomenon, we conducted somatic fusion experiments combining embryogenic suspension-derived protoplasts of Satsuma mandarin, Citrus unshiu Marc. cv. Guoqing No. 1 (G1), a male-sterile cultivar, with leaf protoplasts of other seedy types—Hirado Buntan Pink pummelo (HBP) [Citrus grandis (L.) Osbeck], Sunburst mandarin (C. reticulata Blanco), Orie Lee hybrid (C. reticulata cv. Clementine × Murcott tangor), and Murcott tangor [C. reticulata × C. sinensis (L.) Osbeck], respectively—in an attempt to generate seedless cybrids by the targeted transfer of CMS. The genetic identities of regenerated plants from all four parental combinations were determined by flow cytometry, SSR, CAPS (or PCR-RFLP), RFLP, and chloroplast-SSR analyses. Regenerated plants from the first three parental combinations were diploids, and the cybrid nature of G1 + HBP with the mitochondrion genome from G1 and the chloroplast genome from HBP was confirmed, whereas the cybrid nature of the remaining two combinations was difficult to confirm because of the close phylogenetic relatedness of both fusion parents, as expected. Plants from G1 + Murcott were confirmed as tetraploid somatic hybrids. This is the first report of targeted citrus cybrid production by symmetric fusion with male-sterile Satsuma as the callus parent and other seedy cultivars as the leaf parents.Abbreviations CAPS: Cleaved amplified polymorphic sequence - CMS: Cytoplasmic male sterility - cp-SSR: Chloroplast simple sequence repeat - PEG: Polyethylene glycol - SSR: Simple sequence repeat - RFLP: Restriction fragment length polymorphism Communicated by G.C. Phillips     

In vitro and in vivo prevention of HIV protease inhibitor-induced insulin resistance by a novel small molecule insulin receptor activator

Protease inhibitor (PI) therapy for the treatment of patients infected with human immunodeficiency virus is frequently associated with insulin resistance and diabetic complications. These adverse effects of PI treatment result to a large extent from their inhibition of insulin-stimulated glucose transport. Insulin receptor (IR) activators that enhance the insulin signaling pathway could be effective in treating this resistance. However, there are no agents reported that reverse inhibition of insulin action by PIs. Herein, we describe the effects of TLK19781. This compound is a non-peptide, small molecule, activator of the IR. We now report in cultured cells, made insulin resistant HIV by PI treatment, that TLK19781 both increased the content of insulin-stimulated GLUT4 at the plasma membrane, and enhanced insulin-stimulated glucose transport. In addition, oral administration of TLK19781 with the PI, indinavir improved glucose tolerance in rats made insulin resistant. These results suggest, therefore, that IR activators such as TLK19781 may be useful in treating the insulin resistance associated with PIs.     

Chemoprevention of prostate cancer with selenium: an update on current clinical trials and preclinical findings

Prostate cancer is the most common cancer diagnosed and the second leading cause of cancer-related deaths in men in the United States. The etiological factors that give rise to prostate cancer are not known. Therefore, it is not possible to develop primary intervention strategies to remove the causative agents from the environment. However, secondary intervention strategies with selenium (Se) compounds and other agents represent a viable option to reduce the morbidity and mortality of prostate cancer. In this review, we discuss ongoing clinical trials. In addition, we discuss preclinical mechanistic studies that provide insights into the biochemical and molecular basis for the anti-carcinogenic activity of both inorganic and organic forms of Se.     

DNA damage and cytotoxicity induced by minor groove binding methyl sulfonate esters

Minor groove specific DNA equilibrium binding peptides (lex) based on N-methylpyrrole-carboxamide and/or N-methylimidazolecarboxamide subunits have been modified with an O-methyl sulfonate ester functionality to target DNA methylation in the minor groove at Ade/Thy- and/or Gua/Cyt-rich sequences. HPLC and sequencing gel analyses show that the Me-lex compounds all selectively react with DNA to afford N3-alkyladenine as a major adduct. The formation of the N3-alkyladenine lesions is sequence-dependent based on the equilibrium binding preferences of the different lex peptides. In addition to the reaction at adenine, the molecules designed to target Gua/Cyt sequences also generate lesions at guanine; however, the methylation is not sequence dependent and takes places in the major groove at the N7-position. To determine if and how the level of the different DNA adducts and the sequence selectivity for their formation affects cytotoxicity, the Me-lex analogues were tested in wild type Escherichia coli and in mutant strains defective in base excision repair (tag and/or alkA or apn). The results demonstrate the importance of 3-methyladenine, and in some cases 3-methylguanine, lesions in cellular toxicity, and the dominant protective role of the DNA glycosylases. There is no evidence that the sequence specificity is related to toxicity.     

The Werner syndrome protein stimulates DNA polymerase beta strand displacement synthesis via its helicase activity

Werner syndrome is a hereditary premature aging disorder characterized by genomic instability. Genetic analysis and protein interaction studies indicate that the defective gene product (WRN) may play an important role in DNA replication, recombination, and repair. DNA polymerase beta (pol beta) is a central participant in both short and long-patch base excision repair (BER) pathways, which function to process most spontaneous, alkylated, and oxidative DNA damage. We report here a physical interaction between WRN and pol beta, and using purified proteins reconstitute of a portion of the long-patch BER pathway to examine a potential role for WRN in this repair response. We demonstrate that WRN stimulates pol beta strand displacement DNA synthesis and that this stimulation is dependent on the helicase activity of WRN. In addition, a truncated WRN protein, containing primarily the helicase domain, retains helicase activity and is sufficient to mediate the stimulation of pol beta. The WRN helicase also unwinds a BER substrate, providing evidence that WRN plays a role in unwinding DNA repair intermediates. Based on these findings, we propose a novel mechanism by which WRN may mediate pol beta-directed long-patch BER.     

Mechanism of biochemical action of substituted 4-methylbenzopyran-2-ones. Part 10: identification of inhibitors for the liver microsomal acetoxycoumarin: protein transacetylase

The quantitative structure-activity relationship (QSAR) studies conducted by us earlier revealed the cardinal role of the pyran ring carbonyl group in the acetoxy polyphenolic compounds for the acetoxy polyphenol:protein transacetylase (TAase) activity. Hence, an attempt was made to examine whether such substrate analogues of benzopyran acetates which lack in the pyran ring carbonyl group, such as 7-acetoxy-2,3-dihydro-2,2-dimethylbenzopyran (BPA), cetachin pentaacetate (CPA) and hematoxylin pentaacetate (HPA) could inhibit the 7,8-diacetoxy-4-methylcoumarin (DAMC):protein (glutathione-S-transferase) transacetylase activity. These compounds were indeed found to remarkably inhibit the TAase activity in a concentration dependent manner and exerted their inhibitory action very rapidly. Further BPA, CPA and HPA were found to abolish the TAase mediated activation of NADPH cytochrome C reductase as well as the inhibition of liver microsome catalyzed aflatoxin B(1) (AFB(1))-DNA binding by DAMC very effectively. These results strongly suggest that the acetoxybenzopyrans merit as potent inhibitors of TAase.