Sustained heat suppresses activation of the BA auxin-responsive promoter in cultured guard cell protoplasts of tree tobacco

Dong, M.*; Bufford, J. L.*; Ono, Yutaka; Church, K.*; Dau, M. Q.*; Michels, K.*; Haughton, M.*; Tallman, G.*

At 32C in media containing an auxin and a cytokinin, cultured guard cell protoplasts (GCP) of Nicotiana glauca (Graham), expand, regenerate cell walls, dedifferentiate, and divide. At 38C, GCP acquire thermotolerance within 24 h but their expansion is limited and they neither regenerate walls nor re-enter the cell cycle. Protoplasts were transformed with BA-mgfp5-ER. After 21 h in media with NAA, 49.0% and 7.9% of GCP transformed with BA-mgfp5-ER expressed GFP at 32C and 38C, respectively. Expression at 38C was not increased by incubating GCP for 48 h or by increasing NAA concentrations 20X. Tiron and N-acetylcysteine, superoxide and HO scavengers, respectively, did not prevent BA suppression at 38C nor did H O suppress BA activation at 32C.