TRANSGENIC AEQUORIN REVEALS ORGAN-SPECIFIC CYTOSOLIC CA2-THALIANA SEEDLINGS( RESPONSES TO ANOXIA IN ARABIDOPSIS)

Using the transgenic AEQUORIN system, we showed that the cotyledons an d leaves of Arabidopsis thaliana seedlings developed a biphasic lumine scence response to anoxia, indicating changes in cytosolic Ca2+ levels . A fast and transient luminescence peak occurred within minutes of an oxia, followed by a second, prolonged luminescence response that laste d 1.5 to 4 h. The Ca2+ channel blockers Gd3+, La3+, and ruthenium red (RR) partially inhibited the first response and promoted a larger and earlier second response, suggesting different origins for these respon ses. Both Gd3+ and RR also partially inhibited anaerobic induction of alcohol dehydrogenase gene expression. However, although anaerobic alc ohol dehydrogenase gene induction occurred in seedlings exposed to wat er-agar medium and in roots, related luminescence responses were absen t. Upon return to normoxia, the luminescence of cotyledons, leaves, an d roots dropped quickly, before increasing again in a Gd3+-, La3+-, et hyleneglycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid-, and RR -sensitive fashion.