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Title: ALTERING THE FATE OF STEM CELLS FROM MIDGUT OF THE INSECT, HELIOTHIS VIRESCENS: THE EFFECT OF CALCIUM IONS

Author
item LOEB, MARCIA - RETIRED USDA, IBL

Submitted to: In Vitro Cellular and Developmental Biology - Animal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2004
Publication Date: 5/1/2004
Citation: Loeb, M.J. 2004. Altering the fate of stem cells from midgut of the insect, heliothis virescens: the effect of calcium ions. In Vitro Cellular and Developmental Biology - Animals. 40:26-A.

Interpretive Summary: The caterpillar of the tobacco budworm, Heliothis virescens, is a serious pest on cotton and many other fruits and vegetables. Everything that these larvae eat, including pesticides, enters the midgut cells and is digested. Therefore, understanding how the midgut is able to make stem cells, and to convert them to normal midgut epithelial cells as it grows and repairs itself after injury, is very important to understanding how to control the tobacco budworm by affecting its midgut. In this work, we have found that excess calcium ion concentration within the gut cells can inhibit multiplication of stem cells and, at the same time, induce production of abnormal cells in the gut epithelium. Cutting back on calcium in the midgut can, conversely, induce production of new stem cells and their development into normal midgut epithelium. Previously, we found that a biochemical pump that regulates the concentration of calcium ions exists in midgut cells. Therefore, if a way can be found to inhibit the calcium pump in living insect larvae, increasing the calcium concentration in midgut cells, we will have developed a new and powerful insecticide that can lower the populations of these pest insects in the field.

Technical Abstract: Cultured stem cells from larval midgut tissue of the lepidopteran, Heliothis virescens, respond to alterations in calcium ion concentration (Ca2+) by differentiating to different phenotypes. Increase in the external calcium ion concentration (Ca2+out ) and increased Ca2+ transport into the cell via Ca channels by use of the Ca2+ ionophore, A23187, or by blocking Ca2+ transport into the cells via the Ca2+ channel blocker, verapamil , induced dose-dependent differentiation of non-midgut type cells such as squamous and scale-like cells but did not induce stem cell proliferation or differentiation to normal larval midgut epithelium. On the other hand, decreasing Ca2+out by adding the Ca2+ chelating agent, EGTA, to the medium, doubled the proliferation of stem cells in culture and doubled the number of cells differentiating to larval types of midgut epithelial cells. The mechanism of these actions is not known.