Antisense expression of mitochondrial ATP synthase subunits OSCP (ATP5) and gamma (ATP3) alters leaf morphology, metabolism and gene expression in Arabidopsis.
ABSTRACT Determination of the role of mitochondrial (mt) ATP synthesis in plant metabolism is complicated by chloroplastic ATP synthesis. To differentiate ATP synthesis from these two organelles, we created transgenic Arabidopsis plants in which two different subunits of the mt ATP synthase, the oligomycin sensitivity-conferring protein (OSCP) (=delta) (ATP5) and the gamma (ATP3) subunit, were expressed individually in antisense orientation under the control of a dexamethasone-inducible promoter. The phenotypic effects of antisense expression were identical for both atp5 and atp3. Seedling lethality resulted from induction during germination in the light, demonstrating the essentiality of both gene products. Reduced expression of either gene resulted in stunting of dark-grown (etiolated) seedlings, downward curling or wavy-edged leaf margins of light-grown plants and ball-shaped unexpanded flowers. Antisense induction reduced total ATP levels in dark-grown (etiolated) seedlings germinated on media lacking sucrose, but increased total ATP levels in induced light-grown plants and in induced dark-grown seedlings germinated on media containing sucrose. Induction reduced transcript levels for two transcription factors (TCP3 and TCP4) whose decreased expression is associated with a similar wavy-edged leaf phenotype in Arabidopsis, and increased transcript levels for dynamin-related proteins whose increased expression is associated with increased mt division. Reduced expression of these subunits of the mt ATP synthase is proposed to disturb cellular redox states, which ultimately manifest downstream as diverse and seemingly unrelated phenotypes.
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ABSTRACT: Although curvature of biological surfaces has been considered from mathematical and biophysical perspectives, its molecular and developmental basis is unclear. We have studied the cin mutant of Antirrhinum, which has crinkly rather than flat leaves. Leaves of cin display excess growth in marginal regions, resulting in a gradual introduction of negative curvature during development. This reflects a change in the shape and the progression of a cell-cycle arrest front moving from the leaf tip toward the base. CIN encodes a TCP protein and is expressed downstream of the arrest front. We propose that CIN promotes zero curvature (flatness) by making cells more sensitive to an arrest signal, particularly in marginal regions.Science 03/2003; 299(5611):1404-7. · 31.20 Impact Factor
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ABSTRACT: The respiratory pathways of glycolysis, the tricarboxylic acid (TCA) cycle and the mitochondrial electron transport chain are ubiquitous throughout nature. They are essential for both energy provision in heterotrophic cells and a wide range of other physiological functions. Although the series of enzymes and proteins that participate in these pathways have long been known, their regulation and control are much less well understood. Further complexity arises due to the extensive interaction among these pathways in particular, and also between cytosolic and mitochondrial metabolism in general. These interactions include those between mitochondrial function in the photosynthetic and photorespiratory processes, amino-acid biosynthesis and the regulation of cellular redox. Recently, a wide range of molecular and biochemical strategies have been adopted to elucidate the functional significance of these interactions.Current Opinion in Plant Biology 07/2004; 7(3):254-61. · 8.46 Impact Factor
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ABSTRACT: A novel chemical induction system for transcription in plants has been developed, taking advantage of the regulatory mechanism of vertebrate steroid hormone receptors. A chimeric transcription of the DNA-binding domain of the yeast transcription factor GAL4, the transactivating domain of the herpes viral protein VP16, and the receptor domain of the rat glucocorticoid receptor (GR). The GVG gene was introduced into transgenic tobacco and Arabidopsis together with a luciferase (Luc) gene which was transcribed from a promoter containing six tandem copies of the GAL4 upstream activating sequence. Induction of luciferase activity was observed when the transgenic tobacco plants were grown on an agar medium containing dexamethasone (DEX), a strong synthetic glucocorticoid. Induction levels of the luciferase activity were well correlated with DEX concentrations in the range from 0.1 to 10 microM and the maximum expression level was over 100 times that of the basal level. Analysis of the induction kinetics by Northern blot analysis showed that the Luc mRNA was first detected 1 h after DEX treatment and increased to the maximum level in 4 h. The stationary induction level and the duration of the induction varied with the glucocorticoid derivative used. The GVG gene activity can also be regulated by DEX in transgenic Arabidopsis plants. The results indicate that a stringent chemical control of transcription can be achieved in plants with the GVG system. Advantages and potential uses of this system are also discussed.The Plant Journal 04/1997; 11(3):605-12. · 6.58 Impact Factor