ARS | Publication request: Redox: another level of regulation in chlorophyll metabolism?

Submitted to: Plant Biology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 31, 2011
Publication Date: August 6, 2011
Citation: Grennan, A.K., Ort, D.R. 2011. Redox: another level of regulation in chlorophyll metabolism? [abstract]. American Society of Plant Biologists. Paper No. P02035.

Technical Abstract: Senescence is a highly regulated developmental process and can be thought of as the final developmental stage of a plant or of its organs. In many ways senescence is a recycling process, as the majority of proteins, lipids, and nucleic acids are dismantled and mobilized from the dying tissues and used to support growth in reproductive and younger tissues. In the chloroplasts of senescing leaves, photoactive chlorophyll must first be catabolized. Chlorophyll catabolism is a highly regulated, stepwise process that yields fluorescent chlorophyll catabolites (FCCs). FCCs are exported from the plastid and ultimately to the vacuole where they are broken down into colorless breakdown products (NCCs). A key enzyme in the chlorophyll degradation process is the Fe-dependent monooxygenase pheophorbide a oxygenase (PaO), responsible for the conversion of Pheide a to red colored catabolite (RCC). The regulation of PaO has been shown to occur at the posttranslational level by a phosphorylation/ dephosphorylation mechanism in canola (Brassica napus). A potential redox active site was recently identified in PaO, opening the possibility of redox playing a role in the regulation, or attenuation, of PaO activity. To examine this possibility, we have used site-directed mutagenesis to change the putative redox active cysteines to serines, allowing us to determine if this site is important for PaO activity.