Regulation of membrane fatty acid composition by temperature in mutants of Arabidopsis with alterations in membrane lipid composition

BACKGROUND: A wide range of cellular responses occur when plants are exposed to elevated temperature, including adjustments in the unsaturation level of membrane fatty acids. Although membrane bound desaturase enzymes mediate these adjustments, it is unknown how they are regulated to achieve these specific membrane compositions. Furthermore, the precise roles that different membrane fatty acid compositions play in photosynthesis are only beginning to be understood. To explore the regulation of the membrane composition and photosynthetic function in response to temperature, we examined the effect of temperature in a collection of mutants with altered membrane lipid fatty acid composition. RESULTS: In agreement with previous studies in other species, the level of unsaturation of membrane fatty acids in Arabidopsis was inversely correlated with growth temperature. The time required for the membrane fatty acids to attain the composition observed at elevated temperature was consistent with the timing required for the synthesis of new fatty acids. Comparisons of temperature-induced fatty acid alterations in membranes were made among several Arabidopsis lines including wild-type Columbia, and the compositional mutants, fad5, fad6, act1 and double mutants, fad7 fad8 and act1 fad6. The results revealed key changes that occur in response to elevated temperature regardless of the specific mutations in the glycerolipid pathway, including marked decreases in trienoic fatty acids and consistent increases in unsaturated 16:0 and in dienoic 18:2 levels. Fluorescence measurements of various mutants indicated that photosynthetic stability as well as whole plant growth at elevated temperature is influenced by certain membrane fatty acid compositions. CONCLUSIONS: The results of this study support the premise that defined proportions of saturated and unsaturated fatty acids in membrane lipids are required for photosynthetic thermostability and acclimation to elevated temperature. The results also suggest that changes in the membrane fatty acid composition brought about in response to temperature are regulated in such a way so as to achieve highly similar unsaturation levels despite mutations that alter the membrane composition prior to a high-temperature exposure. The results from examination of the mutant lines also suggest that interorganellar transfer of fatty acids are involved in mediating temperature-induced membrane alterations, and reveal steps in the fatty acid unsaturation pathway that appear to have key roles in the acclimatization of membranes to high temperature

Tumor Formation in Response to Loss of Chromatin Remodeler Chd5 in Zebrafish

Chromodomain helicase DNA binding protein 5 (CHD5) has been identified as a tumor suppressor in humans. Deletion or mutation of CHD5 has been observed in numerous cancers, including neuroblastoma and melanoma. We hypothesize that chd5 is also a tumor suppressor in zebrafish, a powerful model system to study tumorigenesis. Many genes involved in tumorigenesis are conserved in zebrafish, and they develop fully penetrant tumor phenotypes. We have created chd5 knock-out zebrafish using CRISPR/Cas9 and are monitoring them for tumor development. In addition to the chd5 knock-outs, we are undertaking a double-mutant approach by coupling loss of chd5 with other genes known to be important for tumor formation. Specifically, we are using a mutant form of the oncogene BRAF-V600E and a mutant version of the tumor suppressor tp53. BRAF-V600E is a kinase that promotes cell division. Tp53 is tumor suppressor gene that initiates apoptosis when severe DNA damage occurs. Expression of gain-of-function BRAF-V600E gene creates nevi in zebrafish, similar to the production of moles in humans, but is not sufficient to promote melanoma formation. Tp53 when mutated results in nerve sheath tumors in zebrafish at 8.5 months. When BRAF-V600E mutant is combined with mutant tp53, the fish develop melanomas beginning at 4 months. We have crossed our chd5 knock-out alleles with BRAF-V600E and tp53 to create various mutant lines, and we are examining the resulting progeny for tumor development, specifically melanoma. Establishment of a chd5-dependent tumor model using zebrafish will enable novel studies of the function of CHD5 in human cancers

Plants were germinated and grown for 7 d at 22°C before being shifted to high temperature (29°C)

<p><b>Copyright information:</b></p><p>Taken from "Regulation of membrane fatty acid composition by temperature in mutants of Arabidopsis with alterations in membrane lipid composition"</p><p>BMC Plant Biology 2004;4():17-17.</p><p>Published online 17 Sep 2004</p><p>PMCID:PMC524174.</p><p>Copyright © 2004 Falcone et al; licensee BioMed Central Ltd.</p> Fatty acid profiles of wild-type Arabidopsis were determined by gas chromatographic analysis at the designated times over ten days after the shift to elevated temperature as described in materials and methods

DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy

Funding Information: This material is based upon work supported by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Awards DE-FC02-04ER54698 and DE-AC52-07NA27344. Publisher Copyright: © 2022 IAEA, Vienna.DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.Peer reviewe