JXB Advance Access originally published online on March 5, 2009
Journal of Experimental Botany 2009 60(6):1799-1809; doi:10.1093/jxb/erp056
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RESEARCH PAPER |
Inducible antisense suppression of glycolate oxidase reveals its strong regulation over photosynthesis in rice
1Laboratory of Molecular Plant Physiology, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China
2Key Laboratory of Plant Functional Genomics and Biotechnology, Education Department of Guangdong Province, South China Agricultural University; Guangzhou 510642, China
3College of Life Sciences, South China Normal University, Guangzhou 510640, China
4Department of Biology, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
To whom correspondence should be addressed. E-mail: xpeng{at}scau.edu.cn
Photorespiration is one of the most intensively studied topics in plant biology. While a number of mutants deficient in photorespiratory enzymes have been identified and characterized for their physiological functions, efforts on glycolate oxidase (GLO; EC 1.1.3.15 [EC] ) have not been so successful. This is a report about the generation of transgenic rice (Oryza sativa L.) plants carrying a GLO antisense gene driven by an estradiol-inducible promoter, which allowed for controllable suppressions of GLO and its detailed functional analyses. The GLO-suppressed plants showed typical photorespiration-deficient phenotypes. More intriguingly, it was found that a positive and linear correlation existed between GLO activities and the net photosynthetic rates (PN), and photoinhibition subsequently occurred once PN reduction surpassed 60%, indicating GLO can exert a strong regulation over photosynthesis. Various expression analyses identified that Rubisco activase was transcriptionally suppressed in the GLO-suppressed plants, consistent with the decreased Rubisco activation states. While the substrate glycolate accumulated substantially, few changes were observed for the product glyoxylate, and for some other downstream metabolites or genes as well in the transgenic plants. Further analyses revealed that isocitrate lyase and malate synthase, two key enzymes in the glyoxylate cycle, were highly up-regulated under GLO deficiency. Taken together, the results suggest that GLO is a typical photorespiratory enzyme and that it can exert a strong regulation over photosynthesis, possibly through a feed-back inhibition on Rubisco activase, and that the glyoxylate cycle may be partially activated to compensate for the photorespiratory glyoxylate when GLO is suppressed in rice.
Key words: Glycolate oxidase (GLO), glyoxylate cycle, inducible antisense, photorespiration, photosynthesis, rice
* These authors contributed equally to this work.
Present address: College of Agriculture, Henan University of Science and Technology, Luoyang 471003, China.
Received 8 December 2008; Revised 6 February 2009 Accepted 9 February 2009