Aluminum stress responses and alterations of cytosolic calcium ion concentration in cultured tobacco cells

Abstract

Aluminum (Al) ion is a major factor to limit root growth in acidic soils. Although most Al exists in the apoplastic region, Al induces various intracellular events such as callose production, mitochondrial dysfunction, reactive oxygen species production and the inhibition of cell elongation. We investigated a possible involvement of cytosolic free calcium ([Ca²⁺]_cyt) as a second messenger to evoke other Al responses, using tobacco cells expressing aequorin. Compared to control cells, Al-treated cells exhibited two types of transient increase in [Ca²⁺]_cyt, the first one immediately after a start of Al exposure and the second one from 3-h exposure to Al onwards, and the latter one was closely related to a loss of growth capability. The factors to cause these transient increases in [Ca²⁺]_cyt will be discussed, together with the relationship between [Ca²⁺]_cyt and other Al responses.