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This paper gives a summary of a project to characterize a tobacco aquaporin. The cDNA and gene, including the 5′ upstream region, for the tobacco aquaporin NtAQP1 has been isolated and the encoded protein characterized. The significance of promoter regions for an abscisic acid- and gibberellic acid-induced gene expression could be restricted to a region between -1450 and -1112 upstream of the transcription start point by transient transformation of a bicistronic vector into tobacco protoplasts. NtAQP1 expression in tobacco plants was found to be elevated in flowers, stems and roots. In roots, the protein was detected close to xylem vessels in pitch-like structures. Studies with a NtAQP1-GFP fusion indicated a plasma membrane location. For a functional analysis, the cDNA was expressed in Xenopus oocytes. NtAQP1 was found to be a heavy metal-insensitive aquaporin with additional permeability for glycerol. Mutation of a threonine at position 233 to a cysteine transformed NtAQP1 into a heavy metal-sensitive aquaporin. [ABSTRACT FROM AUTHOR]

Studies the light-induced stomatal movement of selected Arabidopsis thaliana mutants. Detection of the stomatal response to light with a customized gas exchange measurement device; Comparison of the mutant lines to the respective wild type; Significant differences for the phytochrome A, the abscisic acid insensitive and the auxin resistant mutant.

Discusses findings concerning the sensitivity of aquaporins to heavy metal ions and their possible consequences to plant physiology. Significance of membrane water permeability regulation; Selectivity of plasma membrane aquaporins.