Dong, Malia , Bufford, Jennifer , Oono, Yutaka , Church, Kacy , Dau, Minh , Michels, Kara , Haughton, Michael , Tallman, Gary .
Sustained heat suppresses activation of the BA auxin-responsive promoter in cultured guard cell protoplasts of tree tobacco.
At 32°C in media containing an auxin (1-naphthaleneacetic acid; NAA) and a cytokinin (6-benzylaminopurine; BAP), cultured guard cell protoplasts (GCP) of Nicotiana glauca (Graham), tree tobacco, expand, regenerate cell walls, dedifferentiate, and divide. At 38°C, GCP acquire thermotolerance within 24 h but their expansion is limited and they neither regenerate walls nor re-enter the cell cycle. These putative indicators of auxin insensitivity led us to hypothesize that sustained heat suppresses induction of auxin-regulated genes in cultured GCP. Protoplasts were transformed with BA-mgfp5-ER, in which the Pisum sativum L. BA early auxin-responsive promoter regulates transcription of mgfp5-ER encoding thermostable green fluorescent protein (GFP), or with a similar construct containing the 35S-CaMV constitutive promoter. After 21 h at 32°C in media with NAA, 49.0±3.9% of GCP transformed with BA-mgfp5-ER expressed GFP, similar to expression percentages at 32°C and 38°C of GCP transformed with the 35S construct. After 21 h at 38°C in media with NAA, 7.9±1.6% of GCP transformed with BA-mgfp5-ER expressed GFP, similar to the expression percentage at 32°C in media lacking NAA. Expression at 38°C was not increased by incubating GCP for 48 h or by increasing NAA concentrations 20X. Heat-stressed cells can transiently accumulate reactive oxygen species, and H2O2 suppresses auxin-responsive promoter activation in Arabidopsis mesophyll protoplasts. Tiron and N-acetylcysteine, superoxide and H2O2 scavengers, respectively, did not prevent BA suppression at 38°C nor did H2O2 suppress BA activation at 32°C. In cultured GCP, suppression of the BA auxin-responsive promoter by sustained heat does not require superoxide or H2O2. Supported by a grant from the M.J. Murdock Charitable Trust to G.T.
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1 - Michigan State University, Plant Research Laboratory and Department of Plant Biology, East Lansing, Michigan, 48824, USA
2 - Willamette University, Biology
3 - Japan Atomic Energy Agency
4 - University of Kentucky College of Medicine
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM