|Wu, G - PLANT BIOLOGY UOFI URBANA|
|Ortiz-Lopez, Adriana - FORMER USDA URBANA|
Submitted to: Photosynthesis International Congress Symposium Proceedings and Abstracts
Publication Type: Proceedings
Publication Acceptance Date: August 25, 2001
Publication Date: N/A
Technical Abstract: Regulation of chloroplast ATP synthase is more intricate than its counterpartin mitochondria and bacteria. Light-dependent activation of the chloroplast ATP synthase involves redox modulation of a cysteine bridge that is unique to the chloroplast enzyme. However, the role that redox modulation plays in regulation is uncertain. We used site-directed mutagenesis and plant transformation to change the regulatory bridge domain within the ATP synthase of Arabidopsis. We designed four mutations in redox active domain designated as C199S, C205S, C199S/C205S and deletion. These were transformed into wild type Arabidopsis plants. Expression levels of transgenes and original genes into plants were identified by RT-PCR following by restriction digestion. The results showed the transgenes were extensively overexpressed compared with endogenous y-subnit gene. We monitored activation and redox modulation of chloroplast ATP synthase by measuring electrochromic change relaxation kinetics of the dark-adopted transgenic mutant plants after a 3 s of preillumination and four minutes of re-dark adaptation. The relaxation kinetics of the transgenic mutant plants confirmed interference with redox modulation in transgenic plants. Our on-going work is focusing on TMR-maleimide labeling of cysteine residues to quantify the extent of substitution of thiol group in y-subunit of transformed plants and investigating physiological consequences of loss of redox modulation.