- L. Mlynarova (1)
- A. Muras (1)
- J.P.H. Nap (1)
- E. Russel (1)
- J.H.B. Sprakel (1)
- L. Tian (1)
- D.A. Weitz (1)
- X.B. Yang (1)
- Y. Zhao (1)
Reduced seed germination in Arabidopsis over-expressing SWI/SNF2 ATPase genes
Leeggangers, H.A.C.F. ; Folta, A. ; Muras, A. ; Nap, J.P.H. ; Mlynarova, L. - \ 2015
Physiologia Plantarum 153 (2015)2. - ISSN 0031-9317 - p. 318 - 326.
thaliana - dormancy - transcription - maturation - stress - arrest - growth - rna
In the life of flowering plants, seed germination is a critical step to ensure survival into the next generation. Generally the seed prior to germination has been in a dormant state with a low rate of metabolism. In the transition from a dormant seed to a germinating seed, various epigenetic mechanisms play a regulatory role. Here, we demonstrate that the over-expression of chromatin remodeling ATPase genes (AtCHR12 or AtCHR23) reduced the frequency of seed germination in Arabidopsis thaliana up to 30% relative to the wild-type seeds. On the other hand, single loss-of-function mutations of the two genes did not affect seed germination. The reduction of germination in over-expressing mutants was more pronounced in stress conditions (salt or high temperature), showing the impact of the environment. Reduced germinations upon over-expression coincided with increased transcript levels of seed maturation genes and with reduced degradation of their mRNAs stored in dry seeds. Our results indicate that repression of AtCHR12/23 gene expression in germinating wild-type Arabidopsis seeds is required for full germination. This establishes a functional link between chromatin modifiers and regulatory networks towards seed maturation and germination.
Characterisation of antioxidant and antiproliferative acidic polysaccharides from Chinese wolfberry fruits
He, N.W. ; Yang, X.B. ; Jiao, Y.D. ; Tian, L. ; Zhao, Y. - \ 2012
Food Chemistry 133 (2012)3. - ISSN 0308-8146 - p. 978 - 989.
lycium-barbarum polysaccharides - breast-cancer cells - in-vitro - apoptosis - extraction - arrest - growth - anticancer - prevention - cranberry
Wolfberry fruit polysaccharides (WFPs) were isolated by hot-water extraction and ethanol precipitation. With HPLC analysis, WFPs were for the first time identified as acidic polysaccharides with galacturonic acid being the main component monosaccharide (24.9%), followed by galactose (21.3%), arabinose (18.5%), and glucose (15.9%), accounting for up to 80.6% of the molar percentage. WFPs exhibited a high antioxidant activity and a dose-dependent antiproliferative effect, with IC50 values of 134.9, 70.1 and 138.4 mu g/mL against A549, MCF-7 and LoVo cancer cells after 48 h of incubation as estimated by MTT assay, respectively. Flow cytometry analysis showed that WFPs exerted a stimulatory effect on apoptosis of MCF-7 cells, and induced the cell-cycle arrest at the G0/G1 phase, with the observation of intracellular ROS production and DNA damage. The present study demonstrated that these polysaccharides might have the potential to provide significant natural defence against human cancer.
Colloidal gelation of oppositely charged particles
Russel, E. ; Sprakel, J.H.B. ; Kodger, T.E. ; Weitz, D.A. - \ 2012
Soft Matter 8 (2012)33. - ISSN 1744-683X - p. 8697 - 8703.
short-range attraction - polymer mixtures - phase-diagram - gels - systems - microscopy - stability - dynamics - arrest
Colloidal gelation has been extensively studied for the case of purely attractive systems, but little is understood about how colloidal gelation is affected by the presence of repulsive interactions. Here we demonstrate the gelation of a binary system of oppositely charged colloids, in which repulsive interactions compete with attractive interactions. We observe that gelation is controlled by varying the total volume fraction, the interaction strength, and the new tuning parameter of the mixing ratio of the two particle types, and present a state diagram of gelation along all these phase-space coordinates. Contrary to commonly studied purely attractive gels, in which weakly quenched gels are more compact and less tenuous, we find that particles in these binary gels form fewer contacts and the gels become more tenuous as we approach the gel point. This suggests that a different mechanism governs gel formation and ultimate structure in binary gelation: particles are unable to form additional favorable contacts through rearrangements, due to the competition of repulsive interactions between similarly charged colloids and attractive interactions between oppositely charged colloids.