Showing papers by "Antoni R. Slabas published in 2010"
TL;DR: The data suggest that PAH1/2 play a regulatory role in phospholipid synthesis that is analogous to that described in Saccharomyces cerevisiae, however, the target enzymes differ, and key components of the signal transduction pathway do not appear to be conserved.
Abstract: Phospholipid biosynthesis is essential for the construction of most eukaryotic cell membranes, but how this process is regulated in plants remains poorly understood Here, we show that in Arabidopsis thaliana, two Mg2+-dependent phosphatidic acid phosphohydrolases called PAH1 and PAH2 act redundantly to repress phospholipid biosynthesis at the endoplasmic reticulum (ER) Leaves from pah1 pah2 double mutants contain ~18-fold more phospholipid than the wild type and exhibit gross changes in ER morphology, which are consistent with massive membrane overexpansion The net rate of incorporation of [methyl-14C]choline into phosphatidylcholine (PC) is ~18-fold greater in the double mutant, and the transcript abundance of several key genes that encode enzymes involved in phospholipid synthesis is increased In particular, we show that PHOSPHORYLETHANOLAMINE N-METHYLTRANSFERASE1 (PEAMT1) is upregulated at the level of transcription in pah1 pah2 leaves PEAMT catalyzes the first committed step of choline synthesis in Arabidopsis and defines a variant pathway for PC synthesis not found in yeasts or mammals Our data suggest that PAH1/2 play a regulatory role in phospholipid synthesis that is analogous to that described in Saccharomyces cerevisiae However, the target enzymes differ, and key components of the signal transduction pathway do not appear to be conserved
179 citations
TL;DR: The acclimation physiology of selected gene ‘knockouts’ is characterised to elucidate possible gene function in the response and suggest the existence of an early transient phase and a sustained phase to theAcclimation response of PSII.
Abstract: Background: Photosystem II (PSII) is the most thermally sensitive component of photosynthesis. Thermal acclimation of this complex activity is likely to be critically important to the ability of photosynthetic organisms to tolerate temperature changes in the environment. Methodology/Findings: We have analysed gene expression using whole-genome microarrays and monitored alterations in physiology during acclimation of PSII to elevated growth temperature in Synechocystis sp. PCC 6803. PSII acclimation is complete within 480 minutes of exposure to elevated temperature and is associated with a highly dynamic transcriptional response. 176 genes were identified and classified into seven distinct response profile groups. Response profiles suggest the existence of an early transient phase and a sustained phase to the acclimation response. The early phase was characterised by induction of general stress response genes, including heat shock proteins, which are likely to influence PSII thermal stability. The sustained phase consisted of acclimation-specific alterations that are involved in other cellular processes. Sustained responses included genes involved in phycobillisome structure and modification, photosynthesis, respiration, lipid metabolism and motility. Approximately 60% of genes with sustained altered expression levels have no known function. The potential role of differentially expressed genes in thermotolerance and acclimation is discussed. We have characterised the acclimation physiology of selected gene 'knockouts' to elucidate possible gene function in the response. Conclusions/Significance: All mutants show lower PSII rates under normal growth conditions. Basal PSII thermotolerance was affected by mutations in clpB1, cpcC2, hspA, htpG and slr1674. Final PSII thermotolerance was affected by mutations in cpcC2, hik34, hspA and hypA1, suggesting that these gene products play roles in long-term thermal acclimation of PSII.
39 citations
TL;DR: Exogenous ATP and a non‐hydrolysable analogue used as probes to identify the molecular and physiological effects of eATP‐mediated signalling in tobacco reveal several previously unknown putative molecular targets of e ATP signalling, which pinpointeATP as an important hub at which regulatory signals of some major primary metabolic pathways and defence responses are integrated.
Abstract: Extracellular adenosine 5'-triphosphate (eATP) is emerging as an important plant signalling compound capable of mobilising intracellular second messengers such as Ca 2+ , nitric oxide, and reactive oxygen species. However, the downstream molecular targets and the spectrum of physiological processes that eATP regulates are largely unknown. We used exogenous ATP and a non-hydrolysable analogue as probes to identify the molecular and physiological effects of eATP-mediated signalling in tobacco. 2-DE coupled with MS/MS analysis revealed differential protein expression in response to perturbation of eATP signalling. These proteins are in several functional classes that included photosynthesis, mitochondrial ATP synthesis, and defence against oxidative stress, but the biggest response was in the pathogen defence-related proteins. Consistent with this, impairment of eATP signalling induced resistance against the bacterial pathogen Erwinia carotovora subsp. carotovora. In addition, disease resistance activated by a fungal pathogen elicitor (xylanase from Trichoderma viride) was concomitant with eATP depletion. These results reveal several previously unknown putative molecular targets of eATP signalling, which pinpoint eATP as an important hub at which regulatory signals of some major primary metabolic pathways and defence responses are integrated.
34 citations
TL;DR: Key components of the cytochrome b6/f and NADH dehydrogenase complexes, crucial components in electron transport, are approximately twofold more abundant in 38°C thylakoid extracts.
Abstract: Growth temperature has a marked influence on the thermotolerance of photosystem II (PSII), which is the most heat-sensitive component of photosynthesis. Using Synechocystis sp. PCC 6803 we have established that thylakoids isolated from cells grown at 38 degrees C have a greater degree of thermotolerance than those isolated from cells grown at 25 degrees C. Reconstitution experiments using Triton X-100 protein extracts of these thylakoids added to Triton-treated thylakoid membranes further indicated that the 38 degrees C Triton extract contains proteins that are directly capable of enhancing PSII thermotolerance. We have used 4-plex iTRAQ, extensive off-line fractionation and sample re-injection to comprehensively identify the differences between these two preparations that may be responsible for the observed effects on PSII thermotolerance. This has resulted in the reproducible identification of 168 proteins out of a total of 385 distinct proteins. Our results have identified 15 proteins whose levels are increased in extracts that result in increased thermotolerance of PSII and 33 proteins whose levels decrease. Notably, components of the cytochrome b(6)/f and NADH dehydrogenase complexes, crucial components in electron transport, are approximately twofold more abundant in 38 degrees C thylakoid extracts. The possible biological importance of these changes is discussed.
28 citations
TL;DR: It is suggested that the synthesis de novo of fatty acids, as well as proteins, is required for the enhancement of the thermal stability of PSII during the acclimation of Synechocystis cells to high temperature.
22 citations