Cloning of the pleiotropic T locus in soybean and two recessive alleles that differentially affect structure and expression of the encoded flavonoid 3' hydroxylase

Three loci (I, R, and T) control pigmentation of the seed coats in Glycine max and are genetically distinct from those controlling flower color. The T locus also controls color of the trichome hairs. We report the identification and isolation of a flavonoid 3' hydroxylase gene from G. max (GmF3'H) and the linkage of this gene to the T locus. This GmF3'H gene was highly expressed in early stages of seed coat development and was expressed at very low levels or not at all in other tissues. Evidence that the GmF3'H gene is linked to the T locus came from the occurrence of multiple RFLPs in lines with varying alleles of the T locus, as well as in a population of plants segregating at that locus. GmF3'H genomic and cDNA sequence analysis of color mutant lines with varying t alleles revealed a frameshift mutation in one of the alleles. In another line derived from a mutable genetic stock, the abundance of the mRNAs for GmF3'H was dramatically reduced. Isolation of the GmF3'H gene and its identification as the T locus will enable investigation of the pleiotropic effects of the T locus on cell wall integrity and its involvement in the regulation of the multiple branches of the flavonoid pathway in soybean.     

Embryonic development of the false limpet Siphonaria lateralis from Atlantic Patagonia

Siphonariids are pulmonate gastropods inhabiting rocky intertidal habitats, and many studies have focused on these false limpets around the world. In the southern South Atlantic, studies on reproduction and development in species of Siphonaria are scarce. We studied the embryonic development and egg masses of Siphonaria lateralis at its northernmost distribution in Atlantic Patagonia. In S. lateralis, as in most species of Siphonaria, individuals spawn benthic egg masses that strongly attach to intertidal rocky substrata. A single spherical egg that measures ~120 µm develops inside the egg capsule of S. lateralis. Considering the relatively small egg size, and reports from previous studies, the developmental modality of S. lateralis might be expected to include a planktotrophic larval phase. However, we found that hatchlings emerged as 1‐mm crawling juveniles, probably owing to the presence of intracapsular fluid, which may provide the energetic requirements for direct development. The embryonic size changed little from the egg to veliger stages, and then increased rapidly until the hatchling stage. We compared development in S. lateralis with development in the sympatric Siphonaria lessonii, in which egg size was reported to be ~80 µm and hatching occurs as planktotrophic veliger larvae. In these two species, spawn and early intracapsular developmental modes are remarkably different; these differences represent contrasting ways to survive in the harsh and physically stressful intertidal Patagonian coasts.     

Breeding performance and survival in the peregrine falcon Falco peregrinus support an age‐related competence improvement hypothesis mediated via an age threshold

We studied the effects of age on breeding performance and survival probability in a peregrine falcon population, using data from a long term monitoring programme (carried out over 16 yr), in which we were able to identify individual birds. We compared the breeding performance and survival of yearling breeders, first‐time adult breeders and adult breeders. We found significant differences in breeding performance but not in survival. Yearling breeders had lower breeding success than older individuals but the breeding performance of inexperienced adults did not differ from that of experienced adults. We did not find changes in terminal breeding success since peregrines in their last year of life sustained the performance levels shown in previous years although with increasing variability. We found no evidence that attempting to breed affected survival probability in any age group. We argue that differences in breeding performance are related to age, not to breeding experience, and that there is an age threshold, coincident with the development of adult plumage, after which breeding performance is not affected either by age or experience. Peregrines that start breeding as yearlings are likely to have greater lifetime reproductive success than birds entering the breeding pool as adults. Consequently, such birds may represent a set of high quality individuals. Our results support the age‐related competence improvement hypothesis as being the relevant explanation for the increase in breeding performance with age.     

Detección molecular de Toxoplasma gondii en carnes para consumo humano en Ibagué, Colombia

Introduction:

Toxoplasma gondii is a parasite with great zoonotic potential. It can infect a broad range of warm-blooded hosts (including livestock) and causes significant losses in the industry. In humans, it has been described as a pathogen in immunosuppressed people, it affects the fetus development in congenital infections, and is associated with various behavioral disorders in healthy people. Humans can acquire T. gondii by consuming undercooked, contaminated meat.

Objective:

To determine T. gondii positivity (currently unknown) in meat for human consumption (i.e., beef, chicken, and pork) in the city of Ibague, Colombia.

Materials and methods:

We used conventional nested PCR and the T. gondii B1 gene sequence as amplification target. We collected samples of meat (N=186) sold in the urban area of Ibagué (62 beef, 62 chicken, and 62 pork samples) and determined the T. gondii positivity percentage for each type of meat.

Results:

The study found an average of 18.8% positivity for all meat samples, pork having the highest percentage (22.5%; 14/62), followed by beef (19.3%; 12/62) and chicken (14.5%; 9/62). The best-amplified products were sequenced by macrogen and aligned with the B1 gene sequences in GenBank, thereby confirming their identity.

Conclusions:

This is the first study of T. gondii prevalence in meat for human consumption carried out in the city of Ibagué and the department of Tolima. All three types of meat sampled represent a risk for local human infection.     

Influence of short chain fatty acids and lysine on Salmonella typhimurium cadA expression

In Salmonella typhimurium, cadA has a role in virulence expression and is an inducible gene that responds to external lysine concentration. In this study, a strain of S. typhimurium carrying a cadA: lacZ fusion was used to determine if the induction of cadA occurred under different lysine concentrations and mildly acid conditions in the presence of short chain fatty acids. Aliquots of an 18-h culture of S. typhimurium were placed on fresh media containing different lysine concentrations at pH 5.8 adjusted by addition of HCl or by 1 M short chain fatty acids (SCFA, acetic, propionic and butyric acid) stock solution. After an induction period of 2 h, -galactosidase activities were assayed. Expression of cadA in rich medium was significantly higher than that of minimal medium at neutral pH and different lysine concentrations. In contrast, at pH 5.8, there was a significant increase in cadA expression, particularly when pH was adjusted using HCl at all lysine levels. Addition of a mixture of organic acids yielded an overall lower cadA expression at all lysine levels studied when compared to HCl. However, each SCFA challenge (individual or as a mixture) caused a high level of expression, both at neutral and acidic pH. Based on these results it is apparent that in the presence of external lysine, SCFA and nutrient availability can influence cadA expression in S. typhimurium.     

Antagonism between salicylic and abscisic acid reflects early host–pathogen conflict and moulds plant defence responses

The importance of phytohormone balance is increasingly recognized as central to the outcome of plant–pathogen interactions. Recently it has been demonstrated that abscisic acid signalling pathways are utilized by the bacterial phytopathogen Pseudomonas syringae to promote pathogenesis. In this study, we examined the dynamics, inter-relationship and impact of three key acidic phytohormones, salicylic acid, abscisic acid and jasmonic acid, and the bacterial virulence factor, coronatine, during progression of P. syringae infection of Arabidopsis thaliana . We show that levels of SA and ABA, but not JA, appear to play important early roles in determining the outcome of the infection process. SA is required in order to mount a full innate immune responses, while bacterial effectors act rapidly to activate ABA biosynthesis. ABA suppresses inducible innate immune responses by down-regulating SA biosynthesis and SA-mediated defences. Mutant analyses indicated that endogenous ABA levels represent an important reservoir that is necessary for effector suppression of plant-inducible innate defence responses and SA synthesis prior to subsequent pathogen-induced increases in ABA. Enhanced susceptibility due to loss of SA-mediated basal resistance is epistatically dominant over acquired resistance due to ABA deficiency, although ABA also contributes to symptom development. We conclude that pathogen-modulated ABA signalling rapidly antagonizes SA-mediated defences. We predict that hormonal perturbations, either induced or as a result of environmental stress, have a marked impact on pathological outcomes, and we provide a mechanistic basis for understanding priming events in plant defence.     

Early life history of the Mediterranean gorgonian Paramuricea clavata: implications for population dynamics

Abstract. Knowledge about early stages of marine sessile invertebrates dispersing by means of free-swimming propagules is fundamental toward understanding their population biology. In this study, we describe and quantify survivorship of early stages of the gorgonian Paramuricea clavata to contribute to the understanding of their implications on population dynamics of this emblematic species of the Mediterranean hard-bottom communities. Spawning was recorded in June for the 3 years studied (2001–2003). High levels of fertilization rate were observed during the main spawning in 2001 and 2002 (62–69%). This appears to be related to the surface brooding mode of development, synchronous spawning, and high fecundity of the species. The timing of development of the blastulae was ∼24 h and the planulae appeared after 48–72 h. In the laboratory, metamorphosis into polyp started between 8 and 25 d, but this timing may have been delayed by lack of unknown appropriate cues for settlement. The behavior of first developed planulae exhibited a marked negative phototaxis that may be a strategy to avoid competition with fast-growing algae on photophilous habitats. Despite the high fertilization rate in P. clavata , laboratory and field experiences indicate that survivorship through the planulae and polyp stages was very low, given that none of the settled polyps survived for >7 months in both experimental years. The low survival of the early stages may help explain the low recruitment rates observed in the field in addition to indicating major limitations for colonization of new areas and for persistence of the local population under disturbances.