High triacylglycerol turnover is required for efficient opening of stomata during heat stress in Arabidopsis

Heat stress triggers the accumulation of triacylglycerols in Arabidopsis leaves, which increases basal thermotolerance. However, how triacylglycerol synthesis is linked to thermotolerance remains unclear and the mechanisms involved remain to be elucidated. It has been shown that triacylglycerol and starch degradation are required to provide energy for stomatal opening induced by blue light at dawn. To investigate whether triacylglycerol turnover is involved in heat-induced stomatal opening during the day, we performed feeding experiments with labeled fatty acids. Heat stress strongly induced both triacylglycerol synthesis and degradation to channel fatty acids destined for peroxisomal ß-oxidation through the triacylglycerol pool. Analysis of mutants defective in triacylglycerol synthesis or peroxisomal fatty acid uptake revealed that triacylglycerol turnover and fatty acid catabolism are required for heat-induced stomatal opening in illuminated leaves. We show that triacylglycerol turnover is continuous (1.2 mol% per min) in illuminated leaves even at 22°C. The ß-oxidation of triacylglycerol-derived fatty acids generates C₂ carbon units that are channeled into the tricarboxylic acid pathway in the light. In addition, carbohydrate catabolism is required to provide oxaloacetate as an acceptor for peroxisomal acetyl-CoA and maintain the tricarboxylic acid pathway for energy and amino acid production during the day.

1,135 ionomes reveal the global pattern of leaf and seed mineral nutrient and trace element diversity in Arabidopsis thaliana

Soil is a heterogeneous reservoir of essential elements needed for plant growth and development. Plants have evolved mechanisms to balance their nutritional needs based on availability of nutrients. This has led to genetically based variation in the elemental composition, the 'ionome', of plants, both within and between species. We explore this natural variation using a panel of wild-collected, geographically widespread Arabidopsis thaliana accessions from the 1001 Genomes Project including over 1,135 accessions, and the 19 parental accessions of the Multi-parent Advanced Generation Inter-Cross (MAGIC) panel, all with full-genome sequences available. We present an experimental design pipeline for high-throughput ionomic screenings and analyses with improved normalisation procedures to account for errors and variability in conditions often encountered in large-scale, high-throughput data collection. We report quantification of the complete leaf and seed ionome of the entire collection using this pipeline and a digital tool, Ion Explorer, to interact with the dataset. We describe the pattern of natural ionomic variation across the A. thaliana species and identify several accessions with extreme ionomic profiles. It forms a valuable resource for exploratory genetic mapping studies to identify genes underlying natural variation in leaf and seed ionome and genetic adaptation of plants to soil conditions.

Randomized controlled trial on the efficacy of new alcohol-free chlorhexidine mouthrinses after 8 weeks

OBJECTIVES

To evaluate the efficacy of two alcohol-free antimicrobial mouthrinses in reducing plaque and gingivitis compared to an alcohol-containing rinse and toothbrushing alone.

METHODS

One hundred and sixty healthy volunteers were enrolled in the randomized controlled trial. Participants were randomly and equally assigned to four groups: (i) toothbrushing + rinsing (0.06% CHX + 0.025% NaF, alcohol-containing rinse, positive control); (ii) toothbrushing + rinsing (0.06% CHX + 0.025% NaF, alcohol-free experimental rinse); (iii) toothbrushing + rinsing (0.06% CHX + 0.03% CPC + 0.025% NaF, alcohol-free experimental rinse); (iv) toothbrushing alone (negative control). At baseline, Quigley-Hein plaque index (QHI), modified proximal plaque index (MPPI), and papillary bleeding index (PBI) were recorded. All subjects brushed their teeth as usual during the study. Additionally, groups 1-3 rinsed twice daily. Eight weeks after baseline, indices were recorded again. anova with Bonferroni adjustment served for statistical analysis.

RESULTS

One hundred and fifty-five participants were included into final analysis (i: n = 39, 2: n = 39, 3: n = 37, 4: n = 40). Experimental rinses (ii, iii) reduced QHI and MPPI to a higher extent than the negative control (iv), whereas no significant difference to the positive control was found. QHI: (i) 36.6%, (ii) 32.3%, (iii) 36.8%, (iv) 21.6%; MPPI: (i) 11.9%, (ii) 12.2%, (iii) 13.6%, (iv) 3.5%. For PBI, no statistically significant difference was found between groups: (i) 80.2%, (ii) 77.8%, (iii) 76.5% and (iv) 78.8%.

CONCLUSIONS

With respect to QHI and MPPI, toothbrushing in combination with any rinse was more effective than toothbrushing alone. No statistically significant differences were found between the alcohol-free and the alcohol-containing control rinses.

Massive genomic variation and strong selection in Arabidopsis thaliana lines from Sweden

Despite advances in sequencing, the goal of obtaining a comprehensive view of genetic variation in populations is still far from reached. We sequenced 180 lines of A. thaliana from Sweden to obtain as complete a picture as possible of variation in a single region. Whereas simple polymorphisms in the unique portion of the genome are readily identified, other polymorphisms are not. The massive variation in genome size identified by flow cytometry seems largely to be due to 45S rDNA copy number variation, with lines from northern Sweden having particularly large numbers of copies. Strong selection is evident in the form of long-range linkage disequilibrium (LD), as well as in LD between nearby compensatory mutations. Many footprints of selective sweeps were found in lines from northern Sweden, and a massive global sweep was shown to have involved a 700-kb transposition.

[Iris sutures for refixation of decentered intraocular lenses]

BACKGROUND

Most revisions after intraocular lens (IOL) implantation are due to an insufficiency of the zonular apparatus. Frequently, an inferior decentration can be seen ("sunset syndrome"). In this clinical study, suture refixation of the haptics to the iris was assessed. Functional and morphological results were considered.

METHOD

21 eyes with subluxation of the IOL were treated with iris sutures for refixation. The operation was performed under topical and intracameral anaesthesia. Refixation was achieved by suturing one or both haptics to one or two fixation points in the outer periphery of the iris. Complete zonular dialysis made it necessary to suture at two fixation spots. All eyes were examined preoperatively, at one day and three months postoperatively considering functional results and postoperative IOL centration.

RESULTS

In 15 eyes (71%), the IOL was optimally centred postoperatively. In 5 eyes (24%), a revision had to be performed due to instable centration. In one further case the IOL was minimally decentred, but its position was stable. Best corrected visual acuity was 0.3 +/- 0.2 preoperatively and 0.5 +/- 0.2 after three months. The mean refraction was stable in the postoperative course and astigmatism did not change significantly. There were no major complications intraoperatively or postoperatively, but a localised iris atrophy at the haptic fixation points was noted.

CONCLUSIONS

In the presence of a partially intact zonular apparatus, iris sutures are a safe and minimally invasive method for fixing a decentred IOL. Postoperative centration and functional results were stable after 3 months.