Endophytic colonization of sugarcane (Saccharum officinarum) by the novel diazotrophs Shinella sp. UYSO24 and Enterobacter sp. UYSO10

Plant and Soil - Sugarcane is a multipurpose crop mostly used in Uruguay for bioethanol production. It requires high amounts of N fertilization for optimal growth, which causes environmental...     

Asymmetric Response to Heterotypic Distress Calls in the Lizard Liolaemus chiliensis

The weeping lizard, Liolaemus chiliensis, emits distress calls when trapped by a predator. Conspecific lizards respond to such calls with prolonged immobility, which may increase their probability of remaining undetected by a predator. This benefit, however, depends on the ability to react to the alert message of the call, which may be impaired by natural variation in the calls. The distress calls of L. chiliensis show geographic variation, and here we tested the response of two geographically distant populations (>700 km apart) to local (homotypic) and non‐local (heterotypic) distress calls; if populations are finely tuned to their local calls, they may not be able to respond to heterotypic calls. We found that geographic variation in calls affects the lizards’ response, but this effect was population dependent; whereas southern lizards responded to calls of both populations, the northern lizards only reacted to homotypic distress calls. The factors that determine this asymmetric response to heterotypic calls are unclear and we discuss three hypotheses that have a common component in the difference in body size between the tested populations, which seems to play a key role in determining the response to distress calls in this species.     

Sex Distribution of Paper Mulberry (Broussonetia papyrifera) in the Pacific

BackgroundPaper mulberry (Broussonetia papyrifera (L.) L''Hér. ex Vent) is a dioecious tree native to East Asia and mainland Southeast-Asia, introduced prehistorically to Polynesia as a source of bark fiber by Austronesian-speaking voyagers. In Oceania, trees are coppiced and harvested for production of bark-cloth, so flowering is generally unknown. A survey of botanical records of paper mulberry revealed a distributional disjunction: the tree is apparently absent in Borneo and the Philippines. A subsequent study of chloroplast haplotypes linked paper mulberry of Remote Oceania directly to a population in southern Taiwan, distinct from known populations in mainland Southeast-Asia.MethodologyWe describe the optimization and use of a DNA marker designed to identify sex in paper mulberry. We used this marker to determine the sex distribution in selected localities across Asia, Near and Remote Oceania. We also characterized all samples using the ribosomal internal transcribed spacer sequence (ITS) in order to relate results to a previous survey of ITS diversity.ResultsIn Near and Remote Oceania, contemporary paper mulberry plants are all female with the exception of Hawaii, where plants of both sexes are found. In its natural range in Asia, male and female plants are found, as expected. Male plants in Hawaii display an East Asian ITS genotype, consistent with modern introduction, while females in Remote Oceania share a distinctive variant.ConclusionsMost paper mulberry plants now present in the Pacific appear to be descended from female clones introduced prehistorically. In Hawaii, the presence of male and female plants is thought to reflect a dual origin, one a prehistoric female introduction and the other a modern male introduction by Japanese/Chinese immigrants. If only female clones were dispersed from a source-region in Taiwan, this may explain the absence of botanical records and breeding populations in the Philippines and Borneo, and Remote Oceania.     

Analysis of Rhizobium meliloti Sym Mutants Obtained by Heat Treatment

Deletions in the pSym megaplasmid of Rhizobium meliloti were produced at a high frequency, and their lengths varied according to incubation temperature. Morphological differentiation into large and small colonies occurred after heat treatment. Small colonies elicited pseudonodules on alfalfa roots.     

Method for Testing Degree of Infectivity of Rhizobium meliloti Strains

The infectiveness of different strains of Rhizobium meliloti was tested with a technique that uses the addition of tetracycline to the root medium. To stop the infection, the antibiotic was added some time after the inoculation of Medicago sativa plants. A coefficient of infectivity for each strain was calculated according to the number of nodules that appeared with and without the addition of the antibiotic. This method seems useful in infectivity studies and is simpler and easier to perform than the test of competence between strains.     

Proliferation and differentiation of human adipocyte precursor cells: Differences between the preperitoneal and subcutaneous compartments

Human adipocyte precursor cells (APC) have been characterized in their proliferation and differentiation potential from subcutaneous, omental, and mesenteric depots, mostly from morbidly obese patients. Cells from the preperitoneal adipose compartment have not been characterized yet, least of all when obtained from normal weight subjects. The aim was to compare proliferation and differentiation of subcutaneous (SC) and preperitoneal (PP) APC derived from adipose tissue in healthy subjects with different body mass. SC and PP adipose tissue was obtained during surgery of inguinal hernias in five healthy non‐obese subjects and three obese otherwise healthy men. APC, obtained by collagenase digestion, were cultured. Proliferation was assayed by cell counting and differentiation by oil red O staining and flow cytometry using Nile Red staining. Proliferation of SC was higher than PP APC. Such differences between both compartments were even higher in APC obtained from obese patients. Conversely PP APC differentiated earlier in vitro compared with SC cells. These results agree with published data on fat cell proliferation. However regarding differentiation, our data show that APC from deeper depots (in this case PP) differentiate earlier than subcutaneous APC. This is different to previous studies performed in mesenteric or omental adipose tissue. J. Cell. Biochem. 111: 659–664, 2010. © 2010 Wiley‐Liss, Inc.     

Acute inhibition of iron bioavailability by zinc: studies in humans

Iron (Fe) and zinc (Zn) deficiencies constitute two of the most important nutritional and public health problems affecting developing countries. Combined supplementation or fortification with Zn and Fe are strategies that can be used to improve the Zn and Fe status of a population. However, there is concern about potential negative interactions between these two micronutrients due to a competitive binding to DMT1 and Zip14 transporter. Studies performed in humans have shown an inhibitory effect of Zn on Fe absorption when both minerals are given together as a solution in fasting conditions. We found that at low doses of iron (0.5 mg) the threshold for the inhibition of iron bioavailability was at a Zn:Fe wt/wt ratio ≥5.9:1, whereas at higher doses of Fe (10 mg) this inhibition occurred at 1:1 Zn:Fe wt/wt ratio. This differential response could be explained by the variation in the abundance of both cations as they compete for a limited number of shared transporters at the enterocyte. Conflicting results have been obtained when this interaction was studied in different food matrices. A negative interaction was not observed when Fe and Zn were provided in a composite hamburger meal, premature formula, human milk, or cow milk. A decrease on Fe absorption was observed in only 1 of 3 studies when Fe and Zn were supplied in wheat flour. The possibility of a negative interaction should be considered for supplementation or fortification programs with both microminerals.