QTLs and candidate genes for desiccation and abscisic acid content in maize kernels

Background

Kernel moisture at harvest is an important trait since a low value is required to prevent unexpected early germination and ensure seed preservation. It is also well known that early germination occurs in viviparous mutants, which are impaired in abscisic acid (ABA) biosynthesis. To provide some insight into the genetic determinism of kernel desiccation in maize, quantitative trait loci (QTLs) were detected for traits related to kernel moisture and ABA content in both embryo and endosperm during kernel desiccation. In parallel, the expression and mapping of genes involved in kernel desiccation and ABA biosynthesis, were examined to detect candidate genes.

Results

The use of an intermated recombinant inbred line population allowed for precise QTL mapping. For 29 traits examined in an unreplicated time course trial of days after pollination, a total of 78 QTLs were detected, 43 being related to kernel desiccation, 15 to kernel weight and 20 to ABA content. Multi QTL models explained 35 to 50% of the phenotypic variation for traits related to water status, indicating a large genetic control amenable to breeding. Ten of the 20 loci controlling ABA content colocated with previously detected QTLs controlling water status and ABA content in water stressed leaves. Mapping of candidate genes associated with kernel desiccation and ABA biosynthesis revealed several colocations between genes with putative functions and QTLs. Parallel investigation via RT-PCR experiments showed that the expression patterns of the ABA-responsive Rab17 and Rab28 genes as well as the late embryogenesis abundant Emb5 and aquaporin genes were related to desiccation rate and parental allele effect. Database searches led to the identification and mapping of two zeaxanthin epoxidase (ZEP) and five novel 9-cis-epoxycarotenoid dioxygenase (NCED) related genes, both gene families being involved in ABA biosynthesis. The expression of these genes appeared independent in the embryo and endosperm and not correlated with ABA content in either tissue.

Conclusions

A high resolution QTL map for kernel desiccation and ABA content in embryo and endosperm showed several precise colocations between desiccation and ABA traits. Five new members of the maize NCED gene family and another maize ZEP gene were identified and mapped. Among all the identified candidates, aquaporins and members of the Responsive to ABA gene family appeared better candidates than NCEDs and ZEPs.     

Vergleichende Untersuchung von Jugendentwicklung und Zugverhalten bei Garten- und Hausrotschwanz,Phoenicurus phoenicurus undPh. ochruros

Zusammenfassung An je 12 handaufgezogenen Garten- und Hausrotschwänzen wurden Jugendmauser, Fettdeposition und Zugunruhe erfaßt und mit entsprechenden Daten freilebender Artgenossen verglichen. Die Daten stimmen gut mit denen freilebender Artgenossen überein. Beim Gartenrotschwanz setzt die Jugendmauser in frühem Alter ein und verläuft rasch, und Fettdeposition und Zugunruhe beginnen, ehe die Mauser beendet wird. Er zeigt das typische Bild eines frühwegziehenden Interkontinentalziehers. Beim Hausrotschwanz hingegen wird die Jugendmauser trotz ihrer großen Länge beendet, bevor Fettdeposition und Zugunruhe einsetzen, und beide haben geringeren Umfang. Er bietet das Bild eines weniger ausgeprägten Ziehers und eines Intrakontinentalziehers. Beide Arten zeigen ihre großen Unterschiede in Jugendentwicklung und Zugverhalten in weitgehend entsprechenden Versuchsbedingungen, vor allem unter ganz ähnlichen photoperiodischen Bedingungen. Das spricht dafür, daß diese Unterschiede einer stark endogenen, wahrscheinlich einer stark genetischen Kontrolle unterliegen. Der Gartenrotschwanz — als Weitstrekkenzieher — entwickelt viel, der Hausrotschwanz — als Kurz- bis Mittelstreckenzieher — weit weniger Nachtunruhe. Die Zeit, in der Nachtunruhe produziert wird, stimmt bei beiden Arten sehr gut mit der Zugzeit überein. Die Nachtunruhe ist daher bei beiden Arten typische Zugunruhe. Die verschiedenen gemessenen Zugunruhewerte stimmen z. T. sehr gut mit den zurückzulegenden Zugstrecken überein, z. T. zeigen sie erhebliche Abweichungen. Prinzipiell lassen sich die Daten jedoch alle gut im Sinne endogener Zug-Zeitprogramme interpretieren, wie sie früher für Sylviiden nachgewiesen wurden. Demnach lassen sich die Vorstellungen endogener Zug-Zeitprogramme nunmehr auf eine weitere Vogelgruppe, nämlich die kleinen Drosselvögel, ausdehnen.

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A comparative study of juvenile development, migratory restlessness and migratory behaviour in the Redstart and Black Redstart

Summary Juvenile development, migratory disposition and migratory activity were investigated in Redstarts and Black Redstarts. In each 12 hand-raised individuals, patterns of juvenile moult, fat deposition and migratory restlessness were determined and compared with corresponding data from freeliving conspecifics. There was good agreement between the data from hand-raised and feral birds. In the Redstart, juvenile moult starts early and proceeds rapidly and fat deposition and migratory restlessness start before the moult has ended. The Redstart is typical for an early departing intercontinental migrant. In the Black Redstart, however, the moult, despite its long duration was clearly separated from the migratory events, and fat deposition and migratory restlessness are both less pronounced than in the Redstart. The patterns of the Black Redstart were typical for a less pronounced or an intracontinental migrant. Both species produced the large differences in juvenile development and migratory behaviour in widely corresponding experimental conditions, above all in very similar photoperiodic conditions. This suggests that these differences were based to a high degree on endogenous, probably genetic factors. The Redstart, as a long-distance migrant, developed a lot, and the Black Redstart, a short- to middle-distance migrant, far less nocturnal restlessness. In both species the period in which nocturnal restlessness developed corresponded very well with the migratory season. Thus this restlessness was typical migratory restlessness. The various measurements of restlessness obtained corresponded in part with the distances covered during migration although there were substantial deviations. In principle, however, all the data can well be interpreted in terms of endogenous time programs for migration as they have been formerly demonstrated for Sylviid species. Thus the concept of these programs can now be extended to another bird group — to small Turdiid species.

     

Renewed hope for a vaccine against the intestinal adult Taenia solium

Review of experimental and observational evidence about various cestode infections of mammalian hosts revives hope for the development of an effective vaccine against adult intestinal tapeworms, the central protagonists in their transmission dynamics. As for Taenia solium, there are abundant immunological data regarding cysticercosis in humans and pigs, but information about human taeniasis is scarce. A single publication reporting protection against T. solium taeniasis by experimental primo infection and by vaccination of an experimental foster host, the immunocompetent female hamster, kindles the hope of a vaccine against the tapeworm to be used in humans, its only natural definitive host.     

Highly conserved residues Asp-197 and His-250 in Agp1 phytochrome control the proton affinity of the chromophore and Pfr formation

The mutants H250A and D197A of Agp1 phytochrome from Agrobacterium tumefaciens were prepared and investigated by different spectroscopic and biochemical methods. Asp-197 and His-250 are highly conserved amino acids and are part of the hydrogen-bonding network that involves the chromophore. Both substitutions cause a destabilization of the protonated chromophore in the Pr state as revealed by resonance Raman and UV-visible absorption spectroscopy. Titration experiments demonstrate a lowering of the pK(a) from 11.1 (wild type) to 8.8 in H250A and 7.2 in D197A. Photoconversion of the mutants does not lead to the Pfr state. H250A is arrested in a meta-Rc-like state in which the chromophore is deprotonated. For H250A and the wild-type protein, deprotonation of the chromophore in meta-Rc is coupled to the release of a proton to the external medium, whereas the subsequent proton re-uptake, linked to the formation of the Pfr state in the wild-type protein, is not observed for H250A. No transient proton exchange with the external medium occurs in D197A, suggesting that Asp-197 may be the proton release group. Both mutants do not undergo the photo-induced protein structural changes that in the wild-type protein are detectable by size exclusion chromatography. These conformational changes are, therefore, attributed to the meta-Rc --> Pfr transition and most likely coupled to the transient proton re-uptake. The present results demonstrate that Asp-197 and His-250 are essential for stabilizing the protonated chromophore structure in the parent Pr state, which is required for the primary photochemical process, and for the complete photo-induced conversion to the Pfr state.     

Effect of high oxygen on placental function in short-term explant cultures

Ex situ culture of human gestational tissues has been routinely used as a model to investigate tissue function. The objective of this study was to determine the effect of varying oxygen concentrations on human term placental explants over a 24-h time period. Specifically, the effect of incubating placental explants in oxygen concentrations of 8%, 21% or 95% on tissue viability, metabolism and cell death was measured by assessing glucose consumption, lactate production, release of lactate dehydrogenase, parathyroid hormone-related protein (PTHrP), tumour necrosis factor-alpha (TNF-α) and 8-isoprostane, immunoreactivity for cleaved-caspase-9 and immunohistochemistry for the caspase-3-cleaved cytokeratin-18 neoepitope, M30. Exposure to higher oxygen concentrations significantly increased the rates of glucose consumption and lactate production. Apoptosis was significantly increased under conditions of higher oxygen as evidenced by increased M30 in placental explant sections. Similarly, hyperoxia significantly increased the releases of PTHrP, TNF-α and 8-isoprostane. Thus, incubation of placental explants with oxygen concentrations of 95% and, to a lesser extent, 21% oxygen was associated with the modulation of multiple cellular response pathways including those associated with tissue viability and cell death. These data are consistent with the hypothesis that hyperoxia activates pathways and mechanisms involved in cellular metabolism, necrosis and apoptosis, thereby shifting the balance from a steady state towards cell death.     

Comparative analysis of expressed genes from cacao meristems infected by Moniliophthora perniciosa

BACKGROUND AND AIMS: Witches' broom disease is caused by the hemibiotrophic basidiomycete Moniliophthora perniciosa, and is one of the most important diseases of cacao in the western hemisphere. Because very little is known about the global process of such disease development, expressed sequence tags (ESTs) were used to identify genes expressed during the Theobroma cacao-Moniliophthora perniciosa interaction. METHODS: Two cDNA libraries corresponding to the resistant (RT) and susceptible (SP) cacao-M. perniciosa interactions were constructed from total RNA, using the DB SMART Creator cDNA library kit (Clontech). Clones were randomly selected, sequenced from the 5' end and analysed using bioinformatics tools including in silico analysis of the differential gene expression. KEY RESULTS: A total of 6884 ESTs were generated from the RT and SP cDNA libraries. These ESTs were composed of 2585 singlets and 341 contigs for a total of 2926 non-redundant sequences. The redundancy of the libraries was low and their specificity high when compared with the few other cacao libraries already published. Sequence analysis allowed the assignment of a putative functional category for 54 % of sequences, whereas approx. 22 % of sequences corresponded to unknown function and approx. 24 % of sequences did not show any significant similarity with other proteins present in the database. Despite the similar overall distribution of the sequences in functional categories between the two libraries, qualitative differences were observed. Genes involved during the defence response to pathogen infection or in programmed cell death were identified, such as pathogenesis related-proteins, trypsin inhibitor or oxalate oxidase, and some of them showed an in silico differential expression between the resistant and the susceptible interactions. CONCLUSIONS: As far as is known this is the first EST resource from the cacao-M. perniciosa interaction and it is believed that it will provide a significant contribution to the understanding of the molecular mechanisms of the resistance and susceptibility of cacao to M. perniciosa, to develop strategies to control witches' broom, and as a source of polymorphism for molecular marker development and marker-assisted selection.     

Preparation and characterization of dinuclear palladium tetraamin-thiophenolate complexes coligated by bridging acetate and acetamidate units

The aromatic thioether (2,6-bis((2-(dimethylamino)ethylamino)methyl)phenyl)(tert-butyl)sulfane (6) reacts with [Pd(NCCH₃)₂Cl₂] under S-C bond cleavage to give the dinuclear palladium(II) complex [L³Pd₂(μ-Cl)]²⁺ (7), where (L³)⁻ = 2,6-bis((2-(dimethylamino)ethylamino)methyl)-thiophenolate. Complex 7 reacts readily with sodium acetate and sodium acetamide by the displacement of the bridging chloride group forming [L³Pd₂(μ-OAc)]²⁺ (8) and [L³Pd₂(μ-ONHCCH₃)]²⁺ (9), respectively. Complex 8 can also be prepared by the reaction of 6 with [Pd(OAc)₂]. All complexes were isolated as perchlorate salts and fully characterized by ESI-MS, IR, ¹H, and ¹³C NMR spectroscopy. The structures of 7[ClO₄] and 9[ClO₄]₂ have been determined by X-ray crystallography. The latter structure reveals a μ_1,3-bridging acetamidate unit showing that (L³)⁻ can alter its conformation sufficiently to accommodate a multi-atom bridging species between the two Pd atoms.     

Iron-uptake in the Euryarchaeon Halobacterium salinarum

Iron-uptake is well studied in a plethora of pro- and eukaryotic organisms with the exception of Archaea, which thrive mainly in extreme environments. In this study, the mechanism of iron transport in the extremely halophilic Euryarchaeon Halobacterium salinarum strain JW 5 was analyzed. Under low-iron growth conditions no siderophores were detectable in culture supernatants. However, various xenosiderophores support growth of H. salinarum. In [⁵⁵Fe]–[¹⁴C] double-label experiments, H. salinarum displays uptake of iron but not of the chelator citrate. Uptake of iron was inhibited by cyanide and at higher concentrations by Ga. Furthermore, a K_M for iron uptake in cells of 2.36 μM and a V_max of approximately 67 pmol Fe/min/mg protein was determined. [⁵⁵Fe]-uptake kinetics were measured in the absence and presence of Ga. Uptake of iron was inhibited merely at very high Ga concentrations. The results indicate an energy dependent iron uptake process in H. salinarum and suggest reduction of the metal at the membrane level.