Effect of kinetin on tuber formation on isolated stolons of Solanum tuberosum L. cultured in vitro

Kinetin-induced tuber formation was investigated with regardto the role of temperature, sucrose concentration, time of kinetinapplication, and inhibitors of protein and nucleic acid biosynthesis.Low temperatures (15°C and 20°C) failed to promote tuberformation in the absence of kinetin, and at 15°C K-inducedtuber formation was partially prevented. Similarly, sucrose concentration per se did not promote tuberformation, however, K-induced tuber formation required a 6%or greater concentration of sucrose in the medium. Stolons preincubated in K prior to incubation on a basal mediumwithout K failed to form tubers but tubers were formed if theywere incubated on a basal medium with K. In order to inducetuber formation, K is only required in the basal medium for3–4 days. Thereafter tuber formation can progress unimpairedon a basal medium only. The inhibitors of protein and nucleic acid synthesis (ACTD,PFA, 2-TU, CHL, 5-FUDR) delayed tuber formation but failed toinhibit the process. The results are discussed in relation to the possible existenceof a tuber forming hormone related to cytokinins and the possibleeffect of temperature on its action. The possibility that tuberformation may be independent of protein and nucleic acid synthesisis also discussed. ¹Present address: Plant Hormone and Regulator Pioneering ResearchLab., U.S. Dept. Agric., Crops Res. Div., Beltsville, Md., U.S.A. (Received October 13, 1969; )     

INGESTION AND EXPECTORATION SAMPLING METHODS OF FOUR TASTES IN A MODEL SYSTEM USING TIME-INTENSITY EVALUATIONS

The objective of this investigation was to compare two sampling methods (expectoration and ingestion) of single component water solutions (sweet—5% sucrose, sour—0.006% citric acid, bitter—0.027% caffeine, salty—0.325% sodium chloride) using time-intensity (T-I) evaluations. Analysis of variance was used to evaluate significant differences. There were subject inconsistencies for the recording times (RT) of sucrose, caffeine and sodium chloride tastes among the sampling methods. No panel differences were found for citric acid duration (RT) between ingested or expectorated samples. Individual contradictions for amplitude sucrose and sodium chloride mixtures were apparent however, the panel demonstrated no differences among the amplitude means between the sampling methods for citric acid and caffeine solutions. Aftertastes for ingested sodium chloride solutions were significantly (P < 0.01) greater than for expectorated samples whereas sampling techniques had no effect upon caffeine aftertastes. Individual contradictions were apparent for citric acid and sucrose aftertastes between the sampling methods.     

Monthly day/night changes and seasonal daily rhythms of sexual steroids in Senegal sole (Solea senegalensis) under natural fluctuating or controlled environmental conditions

In this paper we attempted to investigate the existence of daily fluctuations on plasma sexual steroids (17beta-estradiol, E(2) and testosterone, T) in Senegal sole (Solea senegalensis) females. We described the monthly day/night concentrations and seasonal daily rhythms in animals reared under natural photo- and thermo-period. In addition, the influence of the natural annual fluctuation of the water temperature on the plasma concentration of these steroids was investigated, using one group of Senegal sole under a natural photoperiod, but with an attenuated thermal cycle (around 17-20 degrees C) for one year. Although no significant day/night differences were detected in monthly samplings, the existence of an annual rhythm of E(2) and T (p<0.01) with an acrophase in February was revealed by COSINOR analysis. Maximum values were reached in March for both steroids (6.1+/-1.7 ng mL(-1) at mid-dark, MD and 4.0+/-0.6 ng mL(-1) at mid-light, ML for E2 and 1.4+/-0.4 ng mL(-1) at MD and 0.8+/-0.1 ng mL(-1) at ML for T) in anticipation of the spawning season (May-June). As regards seasonal daily rhythms, the presence of daily oscillations was revealed. At the spring solstice (21st March) a daily rhythm was observed for both steroids (COSINOR, p<0.01), with an acrophase at 20:00 h (E(2)) and at 21:08 h (T). In summer, autumn and winter no daily rhythms were observed due to the low steroid levels at those seasons. When Senegal sole females were submitted to an attenuated annual thermal cycle, the steroid rhythm disappeared (there was no surge in spring, as in the control group) and these fish did not spawn, despite being subjected to natural photoperiod conditions. This result underlined the importance of the natural annual fluctuation of water temperature and photoperiod on the synchronization of the spawning season and on the onset of steroidogenesis.     

Glutamine synthetase sequence evolution in the mycobacteria and their use as molecular markers for Actinobacteria speciation

Background  

Although the gene encoding for glutamine synthetase (gln A) is essential in several organisms, multiple glnA copies have been identified in bacterial genomes such as those of the phylum Actinobacteria, notably the mycobacterial species. Intriguingly, previous reports have shown that only one copy (gln A1) is essential for growth in M. tuberculosis, while the other copies (gln A2, gln A3 and gln A4) are not.     

Changes in genomic methylation patterns during the formation of triploid asexual dandelion lineages

DNA methylation is an epigenetic mechanism that has the potential to affect plant phenotypes and that is responsive to environmental and genomic stresses such as hybridization and polyploidization. We explored de novo methylation variation that arises during the formation of triploid asexual dandelions from diploid sexual mother plants using methylation‐sensitive amplified fragment length polymorphism (MS‐AFLP) analysis. In dandelions, triploid apomictic asexuals are produced from diploid sexual mothers that are fertilized by polyploid pollen donors. We asked whether the ploidy level change that accompanies the formation of new asexual lineages triggers methylation changes that contribute to heritable epigenetic variation within novel asexual lineages. Comparison of MS‐AFLP and AFLP fragment inheritance in a diploid × triploid cross revealed de novo methylation variation between triploid F₁ individuals. Genetically identical offspring of asexual F₁ plants showed modest levels of methylation variation, comparable to background levels as observed among sibs in a long‐established asexual lineage. Thus, the cross between ploidy levels triggered de novo methylation variation between asexual lineages, whereas it did not seem to contribute directly to variation within new asexual lineages. The observed background level of methylation variation suggests that considerable autonomous methylation variation could build up within asexual lineages under natural conditions.     

Influence of Ethylene and Kinetin on Tuberization and Enzyme Activity in Solanum tuberosum L.: Stolons Cultured in vitro

The response of potato stolons, cultured in vitro, to ethylenewas investigated utilizing 2-chloroethyl-phosphonic acid asthe source of ethylene. Concentrations of 0.067, 0.67, 6.7,and 67 µm did not promote tuber formation which occurredin the presence of 16 µm kinetin. In the presence of 2-chloroethyl-phosphonicacid stolon branching was promoted and they maintained a diageotropicgrowth habit in contrast to the negatively geotropic growthhabit of kinetin-treated cultures. The amount of soluble sugars accumulating at the stolon tipwas similar in the presence of kinetin and 2-chloroethylphosphonicacid. However, the level decreased in kinetin-treated stolonsas starch synthesis increased whereas a high specific activitywas maintained in the presence of 2-chloroethylphosphonic acidwhere no starch synthesis occurred. Higher levels of sucroseoccurred in kinetin-treated cultures. Both 2-chloroethylphosphonic acid and kinetin decreased invertaseactivity at the stolon tip. Peroxidase activity increased withtime in response to 2-chloroethylphosphonic acid whereas activityincreased appreciably in kinetin-treated stolons only afterday 5. Generally higher levels of 3'nucleotidase activity existedin 2-chloroethylphosphonic acid-treated stolons. RNase activitydecreased in kinetin treated stolons while activity increasedin the presence of 2-chloroethylphosphonic acid. It is suggestedthat ethylene may influence stolon growth but may not be directlyinvolved in tuber initiation.     

Predicting the current distribution and potential spread of the exotic grass Eragrostis plana Nees in South America and identifying a bioclimatic niche shift during invasion

Eragrostis plana (Poaceae) is a perennial grass introduced from South Africa to the state of Rio Grande do Sul in southern Brazil. Currently, it is considered an invasive grass in several regions of the world, including South America, where it has caused negative ecological and socio‐economic impacts. Ecological niche models, using bioclimatic variables, are often used to predict the potential distribution of invasive species. In this study we prepared two bioclimatic models for E. plana using the Genetic Algorithm for Rule‐set Production, the first based on data from its native region (South Africa) and the second on data from both the native and invaded (South America) regions. We then projected each model onto South America to identify regions vulnerable to invasion by the species, and compared our results with available records of the species in South America. Finally, we explored the model's predictions for the existence of a bioclimatic niche shift during the invasion process of E. plana in South America, using multivariate statistical analysis. The model created with native distribution data was only able to predict (with highly suitable habitat) the region of introduction of E. plana in South America. However, the current distribution, as well as the region of introduction of the species, was reliably predicted by the model created with data from both native and invaded regions. Our multivariate analysis supports a hypothesis of bioclimatic niche shift during the invasion process of E. plana in South America.     

Reset of a critically disturbed microbial ecosystem: faecal transplant in recurrent Clostridium difficile infection

Recurrent Clostridium difficile infection (CDI) can be effectively treated by infusion of a healthy donor faeces suspension. However, it is unclear what factors determine treatment efficacy. By using a phylogenetic microarray platform, we assessed composition, diversity and dynamics of faecal microbiota before, after and during follow-up of the transplantation from a healthy donor to different patients, to elucidate the mechanism of action of faecal infusion. Global composition and network analysis of the microbiota was performed in faecal samples from nine patients with recurrent CDI. Analyses were performed before and after duodenal donor faeces infusion, and during a follow-up of 10 weeks. The microbiota data were compared with that of the healthy donors. All patients successfully recovered. Their intestinal microbiota changed from a low-diversity diseased state, dominated by Proteobacteria and Bacilli, to a more diverse ecosystem resembling that of healthy donors, dominated by Bacteroidetes and Clostridium groups, including butyrate-producing bacteria. We identified specific multi-species networks and signature microbial groups that were either depleted or restored as a result of the treatment. The changes persisted over time. Comprehensive and deep analyses of the microbiota of patients before and after treatment exposed a therapeutic reset from a diseased state towards a healthy profile. The identification of microbial groups that constitute a niche for C. difficile overgrowth, as well as those driving the reinstallation of a healthy intestinal microbiota, could contribute to the development of biomarkers predicting recurrence and treatment outcome, identifying an optimal microbiota composition that could lead to targeted treatment strategies.