Variation in the harvest index of tropical maize: evaluation of recent evidence from Mexico and Malawi

In temperate zones, the potential grain yield of wheat has increased during the twentieth century owing to progressive increases in the harvest index of new varieties, which are principally associated with reduction in plant stature. Crop biomass has not increased substantially. In contrast, the potential grain yield of maize in the USA has increased owing to progressive increases in biomass, principally associated with selection for grain yield at higher population density. Harvest index was already around 0.5 for recommended varieties in 1930, and has not increased significantly since. However, for both crops, the harvest index of a given variety has proved to be a highly‐heritable character, except under severe stress. Less is known about the physiology of tropical maize. This paper reviews evidence from Mexico and Malawi that tropical maize can respond to selection for reduced stature following the same pattern as temperate wheat, but, under other circumstances, the magnitude of harvest index is not highly heritable, varying inconsistently with season, management and environment. It is proposed that these differences arise out of the unique vulnerability of the grain‐setting process around flowering. The plasticity of harvest index under long, favourable conditions, however, remains to be explained, although it is probably also related to the events around grain setting. Nevertheless, to the subsistence farmer, higher harvest index may not be a high priority in crop improvement, because of the need for large quantities of high‐quality stover.     

Nine new polymorphic microsatellite loci for the amplification of archived otolith DNA of Atlantic cod,Gadus morhua L.

Nine out of 22 microsatellite primers tested were successfully amplified on three samples of cod Gadus morhua L. (two contemporary and one archived otolith samples). All loci were polymorphic (5–23 alleles/locus). The average observed heterozygosity across loci and samples was 0.625, ranging from 0.294 to 0.895 at each locus. All loci were under Hardy–Weinberg equilibrium, except PGmo56 that showed significant excess of heterozygotes in all studied samples. The isolated loci were suitable for degraded DNA and therefore useful for conducting a long‐term temporal study with DNA obtained from archived otoliths of cod.     

Oriented thick and thin filaments in amoeba proteus

Actin and myosin filaments as a foundation of contractile systems are well established from ameba to man (3). Wolpert et al. (19) isolated by differential centrifugation from Amoeba proteus a motile fraction composed of filaments which moved upon the addition of ATP. Actin filaments are found in amebas (1, 12, 13) which react with vertebrate heavy meromyosin (HMM), forming arrowhead complexes as vertebrate actin (3, 9), and are prominent within the ectoplasmic tube where some of them are attached to the plasmalemma (1, 12). Thick and thin filaments possessing the morphological characteristics of myosin and actin have been obtained from isolated ameba cytoplasm (18, 19). In addition, there are filaments exhibiting ATPase activity in amebas which react with actin (12, 16, 17). However, giant ameba (Chaos-proteus) shapes are difficult to preserve, and the excellent contributions referred to above are limited by visible distortions occurring in the amebas (rounding up, pseudopods disappearing, and cellular organelles swelling) upon fixation. Achievement of normal ameboid shape in recent glycerination work (15) led us to attempt other electron microscope fixation techniques, resulting in a surprising preservation of A. proteus with a unique orientation of thick and thin filaments in the ectoplasmic region.     

Effect of variety and location on growth and yield components of Roselle,HIbiscus sabdariffa L. and its infestation with the spiny bollworm Earias insulana (BOISD.)

Three roselle, Hibiscus sabdariffa L. varieties (Sudani, Masri and White) were cultivated at three different locations to recognize the transportation ability of roselle cultivation from the narrow old valley land to broad new land in Egypt. Qena as origin in situ old land, El-Kanater as ex situ old land and Nubaria as ex situ new land were the considered locations. Six growth quantitative characters and bolls infestation by spiny bollworm, Earias insulana were evaluated. Growth characters of roselle plants were affected significantly by either variety or location. Qena region was more suitable for roselle plant growth as judged with plant height, number of branches, number of fruits and sepals dry weight, followed by Nubaria followed by El-Kanater. Whereas, plants grown at Nubaria produced more fresh sepals weight than Qena or El-Kanater grown plants. As for Sudani, Nubaria exhibited the tallest plants, with the highest number of fruits and the heaviest fresh sepals as compared with the corresponding plants in Qena or El-Kanater. Values of broad sense heritability were highest for all characters in Qena. While the number of fruits per plant had the highest heritability in all locations. Dry sepals yield had highly significant correlation with all studied characters except percentage of water loss in Qena and Nubaria. Path coefficient analysis confirmed that fresh sepals yield had the highest direct and indirect effects on dried sepals yield. Chemical constituents responsible to sepal quality tended to produce significant variations due to the changes in varieties or locations. The highest levels of anthocyanins and sugars were achieved by Sudani variety, but the highest levels of free amino acids and total soluble solids were recorded for Masri variety. Moreover, Nubaria region was the most favourable for the accumulation of more anthocyanins in the sepals of all varieties followed by Qena. Plants grown at Qena produced sepals with the highest levels of sugars, free amino acids, organic acids and total soluble solids, followed by Nubaria followed by El-Kanater plants. Infestation with spiny bollworm Earias insulana was increased from Sudani up to Masri up to White varieties. Plants grown at Nubaria had the lowest number of attacks by bolls in all varieties, followed by those at El-Kanater followed by Qena plants. Spiny bollworm infestation was positively correlated with the number of branches and dry sepals weight, but negatively correlated with sepal moisture loss and anthocyanin contents. These findings clearly indicated that the Nubaria region was considered as a promising reclaimed area suitable for roselle cultivation, especially for Sudani, the most economic variety.     

A systematic comparative and structural analysis of protein phosphorylation sites based on the mtcPTM database

mtcPTM is an online repository of human and mouse phosphosites in which data are hierarchically organized to preserve biologically relevant experimental information, thus allowing straightforward comparisons of phosphorylation patterns found under different conditions. The database also contains the largest available collection of atomic models of phosphorylatable proteins. Detailed analysis of this structural dataset reveals that phosphorylation sites are found in a heterogeneous range of structural and sequence contexts. mtcPTM is available on the web .     

Protein phosphatase 2A regulatory subunits affecting plant innate immunity,energy metabolism,and flowering time – joint functions among B'η subfamily members

Protein phosphatase 2A (PP2A) is a heterotrimeric complex comprising a catalytic, scaffolding, and regulatory subunit. The regulatory subunits are essential for substrate specificity and localization of the complex and are classified into B/B55, B'', and B” non-related families in higher plants. In Arabidopsis thaliana, the close paralogs B''η, B''θ, B''γ, and B''ζ were further classified into a subfamily of B'' called B''η. Here we present results that consolidate the evidence for a role of the B''η subfamily in regulation of innate immunity, energy metabolism and flowering time. Proliferation of the virulent Pseudomonas syringae in B''θ knockout mutant decreased in comparison with wild type plants. Additionally, B''θ knockout plants were delayed in flowering, and this phenotype was supported by high expression of FLC (FLOWERING LOCUS C). B''ζ knockout seedlings showed growth retardation on sucrose-free medium, indicating a role for B''ζ in energy metabolism. This work provides insight into functions of the B''η subfamily members, highlighting their regulation of shared physiological traits while localizing to distinct cellular compartments.     

Characterization of the genetic diversity of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> in São Paulo city,Brazil

Background

Tuberculosis is a major health problem in São Paulo, Brazil, which is the most populous and one of the most cosmopolitan cities in South America. To characterize the genetic diversity of Mycobacterium tuberculosis in the population of this city, the genotyping techniques of spoligotyping and MIRU were applied to 93 isolates collected in two consecutive years from 93 different tuberculosis patients residing in São Paulo city and attending the Clemente Ferreira Institute (the reference clinic for the treatment of tuberculosis).

Findings

Spoligotyping generated 53 different spoligotype patterns. Fifty-one isolates (54.8%) were grouped into 13 spoligotyping clusters. Seventy- two strains (77.4%) showed spoligotypes described in the international databases (SpolDB4, SITVIT), and 21 (22.6%) showed unidentified patterns. The most frequent spoligotype families were Latin American Mediterranean (LAM) (26 isolates), followed by the T family (24 isolates) and Haarlem (H) (11 isolates), which together accounted for 65.4% of all the isolates. These three families represent the major genotypes found in Africa, Central America, South America and Europe. Six Spoligo-International-types (designated SITs by the database) comprised 51.8% (37/72) of all the identified spoligotypes (SIT53, SIT50, SIT42, SIT60, SIT17 and SIT1). Other SITs found in this study indicated the great genetic diversity of M. tuberculosis, reflecting the remarkable ethnic diversity of São Paulo city inhabitants. The MIRU technique was more discriminatory and did not identify any genetic clusters with 100% similarity among the 93 isolates. The allelic analysis showed that MIRU loci 26, 40, 23 and 10 were the most discriminatory. When MIRU and spoligotyping techniques were combined, all isolates grouped in the 13 spoligotyping clusters were separated.

Conclusions

Our data indicated the genomic stability of over 50% of spoligotypes identified in São Paulo and the great genetic diversity of M. tuberculosis isolates in the remaining SITs, reflecting the large ethnic mix of the São Paulo city inhabitants. The results also indicated that in this city, M. tuberculosis isolates acquired drug resistance independently of genotype and that resistance was more dependent on the selective pressure of treatment failure and the environmental circumstances of patients.

     

Cancer stem cells in solid tumors: elusive or illusive?

Background

The fibroblast growth factor receptor (FGFR) interprets concentration gradients of FGF ligands and structural changes in the heparan sulfate (HS) co-receptor to generate different cellular responses. However, whether the FGFR generates different signals is not known.

Results

We have previously shown in rat mammary fibroblasts that in cells deficient in sulfation, and so in HS co-receptor, FGF-2 can only stimulate a transient phosphorylation of p42/44^MAPK and so cannot stimulate DNA synthesis. Here we demonstrate that this is because in the absence of HS, FGF-2 fails to stimulate the phosphorylation of the adaptor FGFR substrate 2 (FRS2). In cells possessing the HS co-receptor, FGF-2 elicits a bell-shaped dose response: optimal concentrations stimulate DNA synthesis, but supramaximal concentrations (≥ 100 ng/mL) have little effect. At optimal concentrations (300 pg/mL) FGF-2 stimulates a sustained dual phosphorylation of p42/44^MAPK and tyrosine phosphorylation of FRS2. In contrast, 100 ng/mL FGF-2 only stimulates a transient early peak of p42/44^MAPK phosphorylation and fails to stimulate appreciably the phosphorylation of FRS2 on tyrosine.

Conclusions

These results suggest that the nature of the FGFR signal produced is determined by a combination of the HS co-receptor and the concentration of FGF ligand. Both the phosphorylation of the adaptor FRS2, the kinetics (sustained or transient) of phosphorylation of p42/44(MAPK) are varied, and so differing cellular responses are produced.