Organic fertilizers alter the composition of pathogens and arbuscular mycorrhizal fungi in maize roots

Roots of agricultural crops, including maize, are hosts of different microorganisms, many beneficial, like plant growth and health‐promoting arbuscular mycorrhizal fungi (AMF), as well as pathogens including Pythium, Polymyxa and Microdochium. To improve crop nutrition and health, profound knowledge is required regarding how agricultural practices affect field populations of root‐associated microorganisms. Hence, the objective of this work was to evaluate the effect of crop genotype and organic fertilizers on the plant growth performance of maize and their root‐associated microorganisms. The experiment was conducted as a fully factorial greenhouse pot experiment with maize cultivars (two land races and two hybrids) and organic fertilizers (green manure, cow manure and compost) as the two main factors. Plants were harvested 8 weeks after sowing. In general, the different maize cultivars responded similarly to the applications of the organic fertilizers. Cow manure and compost increased plant growth, whereas green manure had limited effect on plant growth. Root colonization with AMF was reduced by green manure with rape. Infection with the root pathogens Pythium and Polymyxa was reduced by all organic fertilizers, whereas in contrast, infection with Microdochium increased with the majority of the organic fertilizers applied. In conclusion, both maize genotype and organic fertilizers affect the abundance of AMF and root pathogens in maize, which should be considered when developing management strategies of these root‐inhabiting microorganisms.     

Investigating hookworm genomes by comparative analysis of two Ancylostoma species

Background

As a first step to explore the possible relationships existing between the effects of low oxygen pressure in the first trimester placenta and placental pathologies developing from mid-gestation, two subtracted libraries totaling 2304 cDNA clones were constructed. For achieving this, two reciprocal suppressive/subtractive hybridization procedures (SSH) were applied to early (11 weeks) human placental villi after incubation either in normoxic or in hypoxic conditions. The clones from both libraries (1440 hypoxia-specific and 864 normoxia-specific) were spotted on nylon macroarrays. Complex cDNAs probes prepared from placental villi (either from early pregnancy, after hypoxic or normoxic culture conditions, or near term for controls or pathological placentas) were hybridized to the membranes.

Results

Three hundred and fifty nine clones presenting a hybridization signal above the background were sequenced and shown to correspond to 276 different genes. Nine of these genes are mitochondrial, while 267 are nuclear. Specific expression profiles characteristic of preeclampsia (PE) could be identified, as well as profiles specific of intra-uterine growth retardation (IUGR). Focusing on the chromosomal distribution of the fraction of genes that responded in at least one hybridization experiment, we could observe a highly significant chromosomal clustering of 54 genes into 8 chromosomal regions, four of which containing imprinted genes. Comparative mapping data indicate that these imprinted clusters are maintained in synteny in mice, and apparently in cattle and pigs, suggesting that the maintenance of such syntenies is requested for achieving a normal placental physiology in eutherian mammals.

Conclusion

We could demonstrate that genes induced in PE were also genes highly expressed under hypoxic conditions (P = 5.10^-5), which was not the case for isolated IUGR. Highly expressed placental genes may be in syntenies conserved interspecifically, suggesting that the maintenance of such clusters is requested for achieving a normal placental physiology in eutherian mammals.     

Cyclin-dependent kinase inhibitors in maize endosperm and their potential role in endoreduplication

Two maize (Zea mays) cyclin-dependent kinase (CDK) inhibitors, Zeama;KRP;1 and Zeama;KRP;2, were characterized and shown to be expressed in developing endosperm. Similar to the CDK inhibitors in Arabidopsis (Arabidopsis thaliana) and tobacco (Nicotiana tabacum), the maize proteins contain a carboxy-terminal region related to the inhibitory domain of the mammalian Cip/Kip inhibitors. Zeama;KRP;1 is present in the endosperm between 7 and 21 d after pollination, a period that encompasses the onset of endoreduplication, while the Zeama;KRP;2 protein declines during this time. Nevertheless, Zeama;KRP;1 accounts for only part of the CDK inhibitory activity that peaks coincident with the endoreduplication phase of endosperm development. In vitro assays showed that Zeama;KRP;1 and Zeama;KRP;2 are able to inhibit endosperm Cdc2-related CKD activity that associates with p13(Suc1). They were also shown to specifically inhibit cyclin A1;3- and cyclin D5;1-associated CDK activities, but not cyclin B1;3/CDK. Overexpression of Zeama;KRP;1 in maize embryonic calli that ectopically expressed the wheat dwarf virus RepA protein, which counteracts retinoblastoma-related protein function, led to an additional round of DNA replication without nuclear division.     

Exploring the connection unit in the HDAC inhibitor pharmacophore model: novel uracil-based hydroxamates

Starting from the pharmacophore model for HDAC inhibitor design, a novel series of hydroxamates bearing a uracil moiety as connecting unit (CU) has been prepared and tested. Almost all compounds exhibited HDAC inhibiting activity at low nanomolar concentrations, the N-hydroxy-6-(3,4-dihydro-4-oxo-6-benzyl- and -6-phenyl-2-pyrimidinylthio)hexanamides 1d and 1l being more potent than SAHA in enzymatic assays. Such compounds also caused hyperacetylation in NIH3T3 cell core histones and were endowed with interesting antiproliferative and cytodifferentiating effects in human leukemia (HL-60) cells.     

Genetic analyses of endoreduplication in Zea mays endosperm: evidence of sporophytic and zygotic maternal control

Flow cytometry was used to assess the variability of endoreduplication in endosperms of maize inbred lines. Little variation was found between midwestern dent types, and high levels of endoreduplication were observed in popcorns. Endoreduplication is different between inbred lines by 13-18 days after pollination, and flow cytometric analysis of ploidy level was feasible until 20 DAP. To study the genetic regulation of endoreduplication, four inbreds were crossed to B73 and developing endosperms from both parental, reciprocal F(1), and backcross generations were subjected to flow cytometric analysis. Three measurements of endoreduplication were calculated from these data and analyzed as quantitative genetic traits. Multiple models of trait inheritance were considered including triploid, diploid, sporophytic maternal, and maternal and paternal zygotic nuclear inheritance. Maternal zygotic effects, often considered a form of parental imprinting, and maternal sporophytic effects were detected. To test the feasibility of introgressing a high endoreduplication phenotype into a midwestern dent inbred line, a backcross population was generated from B73 x Sg18. Parental and progeny endoreduplication levels were compared and heritabilities assessed. The heritabilities calculated from these data generally agree with the values calculated in the larger crossing experiments.     

Investigating the hows and whys of DNA endoreduplication

Endoreduplication is a form of nuclear polyploidization thatresults in multiple, uniform copies of chromosomes. This processis common in plants and animals, especially in tissues withhigh metabolic activity, and it generally occurs in cells thatare terminally differentiated. In plants, endoreduplicationis well documented in the endosperm and cotyledons of developingseeds, but it also occurs in many tissues throughout the plant.It is thought that endoreduplication provides a mechanism toincrease the level of gene expression, but the function of thisprocess has not been thoroughly investigated. Numerous observationshave been made of endoreduplication, or at least extra cyclesof S-phase, as a consequence of mutations in genes controllingseveral aspects of cell cycle regulation. However, until recentlythere were few studies directed at the molecular mechanismsresponsible for this specialized cell cycle. It is suggestedthat endoreduplication requires nothing more elaborate thana loss of M-phase cyclin-dependent kinase activity and oscillationsin the activity of S-phase cyclin-dependent kinase. Key words: Endoreduplication, gene expression, cell cycle regulation, cyclin-dependent kinase.     

Conduction disturbances related to percutaneous balloon mitral valvuloplasty

During the performance of 280 consecutive percutaneous balloon mitral valvuloplasty operations, two cases of conduction disturbances were reported (0.7%). These rare complications are transient and due to the mechanical pressure of the balloon on the conduction system.