Author
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HIRSCHI, KENDAL - BAYLOR COLLEGE MEDICINE |
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Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/31/1999 Publication Date: N/A Citation: N/A Interpretive Summary: We wanted to investigate certain mechanisms within a plant that control the plant's growth and sensitivity to stress. Therefore, we took a type of tobacco plant and made more copies of a calcium transporter, which is a plant gene. In doing so, we manipulated the plant in such a way as to make it more sensitive to negative environmental conditions such as cold temperatures. Under such stressful circumstances, it required more calcium to survive. By effecting dysfunction, in showing that we could control the plant's health and sensitivity to stresss via this calcium mechanism, we showed that this specific plant gene is critical to these functions. By building on this information in future research studies, we hope to manipulate this plant mechanism in a positive way to enable these plants to grow even in a noxious environment. Technical Abstract: Plant cells maintain a precise balance of cytosolic and extracellular ion concentrations. Vacuolar ion transporters, such as CAX1 (CAlcium eXchanger 1) of Arabidopsis thaliana, are thought to be key mediators of cytosolic ion concentrations. In order to clarify the role of CAX1 in general ion homeostasis, CAX1 gene expression was examined in response to various stimuli. CAX1 was highly expressed in response to exogenous calcium (Ca2+). Transgenic tobacco plants expressing CAX1 displayed symptoms of Ca2+ deficiencies. CAX1- expressing tobacco plants were hypersensitive to an array of ion imbalances and to cold shock. Increased Ca2+ in the media abrogated the ion sensitivity of CAX1- expressing plants and delayed the onset of necrosis. Tobacco plants expressing CAX1 also demonstrated increased Ca2+ accumulation and altered tonoplast- enriched Ca2+ /H+ antiport activity. These results demonstrate that CAX1 expression perturbs snormal Ca2+ homeostasis and markedly increases stress sensitivity. Our findings suggest that Ca2+ signaling in plants differs from that seen in yeast, and that plant-plant heterologous expression is a viable mechanism with which to study gene function via genetic dysfunction. |
