Genetic and physiological relationships in N,P and K mobilisation in some sorghum mutants and parents

Summary The mutation breeding program of alteration in plant type in two local Sorghum varieties resulted in several productive mutants of which 16 are far superior to the parents CRP, CBA and recommended hybrids. An earlier analysis of leaf area and photosynthetic efficiency revealed a diversity of mechanisms between mutants of the same yield group. Differences in the transfer of nutrients from leaf to the panicle were also indicated. Further analysis of the partition of nutrients in the panicle, flag leaf and rachis for N, P and K revealed that most of the mutants are at least equal to the parent in grain N but are superior in N content of flag leaf and rachis. Similarly, three mutants had a higher P content in grain than CRP and all other mutants were equal to CRP. Two mutants had more P in the flag leaf but this was not reflected in the grain. However, no differences were observed for the K content in the flag leaf, grain and rachis. The interrelations of the nutrients in different plant parts suggest that each mutant has a different pattern of nutrient accumulation and transfer. It could be concluded that selection for flag leaf N and P can improve grain N and P. There was no negative association between N and P accumulation in different plant parts. No adverse association was observed for other combinations. A study on the grain digestability of the mutants confirmed that the quality of the protein was not adversely affected in this material. This study indicated that simultaneous improvement of grain yield and grain N, P and K can be obtained even among the few mutants generated in this breeding program contrary to the belief of some cereal breeders that grain yield and its N content have a major negative association limiting the improvement of yield and protein content simultaneously.This study was part of a project supplied by IAEA, Vienna     

Evidence for ATP binding and double-stranded DNA binding by Escherichia coli RecF protein.

RecF protein is one of the important proteins involved in DNA recombination and repair. RecF protein has been shown to bind single-stranded DNA (ssDNA) in the absence of ATP (T. J. Griffin IV and R. D. Kolodner, J. Bacteriol. 172:6291-6299, 1990; M. V. V. S. Madiraju and A. J. Clark, Nucleic Acids Res. 19:6295-6300, 1991). In the present study, using 8-azido-ATP, a photo-affinity analog of ATP, we show that RecF protein binds ATP and that the binding is specific in the presence of DNA. 8-Azido-ATP photo-cross-linking is stimulated in the presence of DNA (both ssDNA and double-stranded DNA [dsDNA]), suggesting that DNA enhances the affinity of RecF protein for ATP. These data suggest that RecF protein possesses independent ATP- and DNA-binding sites. Further, we find that stable RecF protein-dsDNA complexes are obtained in the presence of ATP or ATP-gamma-S [adenosine-5'-O-(3-thio-triphosphate)]. No other nucleoside triphosphates served as necessary cofactors for dsDNA binding, indicating that RecF is an ATP-dependent dsDNA-binding protein. Since a mutation in a putative phosphate-binding motif of RecF protein results in a recF mutant phenotype (S. J. Sandler, B. Chackerian, J. T. Li, and A. J. Clark, Nucleic Acids Res. 20:839-845, 1992), we suggest on the basis of our data that the interactions of RecF protein with ATP, with dsDNA, or with both are physiologically important for understanding RecF protein function in vivo.     

Characterization of mercapturic acid and glutathionyl conjugates of benzo[a]pyrene-7,8-dione by two-dimensional NMR.

Non-K-region polycyclic aromatic hydrocarbon (PAH) o-quinones represent alternative metabolites of PAH trans-dihydro diol proximate carcinogens. These PAH o-quinones react readily with glutathione and N-acetyl-L-cysteine, and these adducts may be responsible for their detoxication. Reactions between benzo[a]pyrene-7,8-dione and either N-acetyl-L-cysteine or glutathione gave three predominant products which were purified by semipreparative reverse-phase high-pressure liquid chromatography and characterized by homonuclear two-dimensional correlation spectroscopy (COSY). The first product corresponded to a Michael type, 1,4-addition product isolated at the level of quinone oxidation. The second product converted to the first and is a presumptive 1,4-addition product isolated at the level of hydroquinone oxidation. The third product was 7,8-dihydroxybenzo[a]pyrene (a hydroquinone) and was formed as a result of the reductive potential of the thiol. Additional proof for the catechol structure was obtained by its conversion to its diacetate and its identity with authentic 7,8-diacetoxybenzo[a]pyrene. The structures of these adducts and intermediates confirm that thiol addition involves formation of the ketol and rearrangement to give a catechol followed by oxidation to yield the quinone adduct. No evidence was obtained for the formation of either bisphenol or bisglutathionyl adducts. The COSY spectra provide the first complete structure of a benzo[a]pyrenyl-peptide conjugate.     

AB0 blood group incompatibility and inbreeding effects: Evidence for an interaction

Summary It is known that consanguinity reduces the chances of maternal-foetal incompatibility but it is not known whether inbreeding influences the expression of the effects of such incompatibility. This paper investigates and finds evidence for an interaction between inbreeding and AB0 blood group incompatibility on the expression of neonatal mortality, sibship precocious mortality, neonatal jaundice, asphyxia, and sex ratio, through screening of 3923 consecutive newborns. Inbreeding and incompatibility individually showed variable effects on the above parameters, but their interaction was such that, in the presence of inbreeding, incompatibility reduced the incidence/relative risk of all the above factors. Such a uniform negative interaction was presumed to be due to homozygosity of some pleiotropic genes caused by inbreeding.     

Preferential binding of Escherichia coli RecF protein to gapped DNA in the presence of adenosine (gamma-thio) triphosphate.

Escherichia coli RecF protein binds, but does not hydrolyze, ATP. To determine the role that ATP binding to RecF plays in RecF protein-mediated DNA binding, we have determined the interaction between RecF protein and single-stranded (ss)DNA, double-stranded (ds)DNA, and dsDNA containing ssDNA regions (gapped [g]DNA) either alone or in various combinations both in the presence and in the absence of adenosine (gamma-thio) triphosphate, gamma-S-ATP, a nonhydrolyzable ATP analog. Protein-DNA complexes were analyzed by electrophoresis on agarose gels and visualized by autoradiography. The type of protein-DNA complexes formed in the presence of gamma-S-ATP was different with each of the DNA substrates and from those formed in the absence of gamma-S-ATP. Competition experiments with various combinations of DNA substrates indicated that RecF protein preferentially bound gDNA in the presence of gamma-S-ATP, and the order of preference of binding was gDNA > dsDNA > ssDNA. Since gDNA has both ds- and ssDNA components, we suggest that the role for ATP in RecF protein-DNA interactions in vivo is to confer specificity of binding to dsDNA-ssDNA junctions, which is necessary for catalyzing DNA repair and recombination.     

Heterosis and components of genetic variation for protein and lysine content in some grain sorghums

Summary Twelve varieties representing six geographical regions and nine taxonomic groups from a World Collection ofSorghum were used in a diallel and line X tester analysis of the nature of genetic variation for protein and lysine content. In a majority of crosses, heterosis was negative for protein, and positive for lysine.Analysis of combining ability indicated that both additive and non-additive variation were important for protein, while the non-additive component was predominant for lysine. Heterosis inlow Xlow andmedium Xlow crosses also indicated the presence of substantial non-allelic gene interactions for both the characters.Associations between protein, lysine and yield in parents were significantly different from those in the hybrids indicating considerable scope for genetic manipulation. Negative correlations between protein and lysine (% protein) and between protein and grain yield were very low. The results indicated that a high level of protein and moderately high lysine may be incorporated in high yielding varieties of sorghum, by using Caudatum kaura, Roxburghii shallu and durra from Nigeria and Sudan in the hybridisation programme.     

Factor analysis in relation to breeding system

The forces of divergence in the cultivated populations of crops belonging to different breeding systems,Sorghum, Pennisetum, Brassica, linseed and wheat, have been examined utilising the centroid method of factor analysis. The populations consisted of mostly elite material of high productivity.Three factors were found to be adequate to account for most of the total communality although upto fourteen variables have been included. The results confirmed that the use of genetic correlation matrices in populations under intensive human selection would change the factor loadings to a considerable degree as compared to environmental correlation matrices.The factor loadings inSorghum indicated the important role of the reproductive factor and the growth factor in the evolution of this genus. In the case ofPennisetum, ear girth, ear length and height were important in the first factor, while early vigour and flowering time were predominant for the second foctor. InBrassica, the data have also indicated that disruptive selection for flowering time had substantially modified factor loadings in ease of the genotypic correlation matrix and had, therefore, substantially modified the course of evolution. In the case of linseed, the inclusion of F₁ hybrids did not change the major conclusions drawn about factor loadings for factors from the genotypic correlation matrix.The number of factors and the loadings did not appear to be directly related to the breeding system but were found to be influenced by the past history of selection. The first factor which contributed the most to the total communality was concerned with reproductive capacity and characters influencing major components of fitness under both human and natural selection.Presented at the 21st annual general conference of the Indian Society of Agricultural Statistics held at Lucknow in February, 1968.     

Sister chromatid exchanges in patients with precancerous and cancerous lesions of cervix uteri

Summary The frequency of sister chromatid exchanges (SCEs) was studied in leucocytes from 46 patients with cervical carcinoma, 89 precancerous lesions, and 43 age-matched control women. The frequency of SCEs was found to be 10.15 ±2.49 in cancer, 8.83±2.15 in precancerous lesions, and 7.55±2.24 in controls. The analyses of SCE data revealed a highly significant (P<0.001) increase in precancerous and cancerous lesions compared to controls. The intra-chromosomal distribution of SCEs revealed a random increase in various chromosomal groups in patients with cancer and dysplasia compared to controls. The mean SCE level among various groups of precancerous lesions according to severity of pathological condition did not show significant differences. However, 70.8% of dysplasia cases revealed SCE levels higher than the average in controls. The increased frequencies of SCEs in the majority of cancer patients and a few, precancerous lesions indicate that individuals with high SCE levels may be at a high risk of developing cancer. Thus the usefulness of SCE levels as a preclinical marker to identify the high risk group of dysplasias needs to be ascertained by follow-up studies; these are in progress.     

Combining ability and maternal effects in Brassica campestris L. var. ‘yellow sarson’

Summary A diallel analysis of combining ability, including maternal effects, genotype X environment interaction and the progress under selection, is reported in three selected crosses of Brassica campestris L. var. yellow sarson, involving 15 types, including 10 four-valved and 5 two-valved types from different parts of India. Twelve characters, including oil content, were studied in the f₁ generation.The investigation has revealed only marginal superiority of f₁'s over the parents for most of the characters related to yield. There was no relation between heterozygosity and stability of performance over environments for yield or its components or for oil content. Substantial maternal effects were observed which also interacted with environments. Creation of variation for primary and secondary branches would be essential for changing yield level in yellow sarson. The presence of limited additive variation available for selection for yield components should be augmented by biparental mating the early segregating generations to break linkages, and was demonstrated by the recombinants obtained when this method was adopted.The magnitude of genotype — environment interactions in this study, as compared with the total genetic components for yield, oil content, number of siliquae on main axis and presence of large reciprocal variances in relation to general and specific combining ability variances for practically all characters, and the large interaction of , narrowed down the expected effectiveness of selection.Biparental mating in the three best crosses yielded three new recombinants outyielding the best check T 10 by the margins of 14%, 39% and 15%, respectively, in the yield trial. These recombinants had more primary branches and secondary branches, larger main axes and more siliquae with an increased number of seeds per siliqua, than any of the F₁'s in this study.