Abstract
Glycolate oxidase (GLO) is a key enzyme in photorespiration, catalyzing the oxidation of glycolate to glyoxylate. Arabidopsis GLO is required for nonhost defense responses to Pseudomonas syringae and for tobacco Pto/AvrPto-mediated defense responses. We previously described identification of rice GLO1 that interacts with a glutaredoxin protein, which in turn interacts with TGA transcription factors. TGA transcription factors are well known to participate in NPR1/NH1-mediated defense signaling, which is crucial to systemic acquired resistance in plants. Here we demonstrate that reduction of rice GLO1 expression leads to enhanced resistance to Xanthomonas oryzae pv oryzae (Xoo). Constitutive silencing of GLO1 leads to programmed cell death, resulting in a lesion-mimic phenotype and lethality or reduced plant growth and development, consistent with previous reports. Inducible silencing of GLO1, employing a dexamethasone-GVG (Gal4 DNA binding domain-VP16 activation domain-glucocorticoid receptor fusion) inducible system, alleviates these detrimental effects. Silencing of GLO1 results in enhanced resistance to Xoo, increased expression of defense regulators NH1, NH3, and WRKY45, and activation of PR1 expression.
Highlights
Photorespiration, which is metabolically coupled with photosynthetic CO2 assimilation, is an intensively studied topic in plant biology
We found that transgenic rice silenced for GLO1 are more resistant to Xanthomonas oryzae pv oryzae (Xoo)
Constitutive GLO1 silencing leads to programmed cell death and reduced plant growth To investigate the possible involvement of glycolate oxidase in rice development and immunity, we devised to reduce the expression of the GLO1 (Os03g0786100) gene using the RNA interference (RNAi) approach
Summary
Photorespiration, which is metabolically coupled with photosynthetic CO2 assimilation (the Calvin cycle), is an intensively studied topic in plant biology. Glycolate oxidase (GLO) is a key enzyme in photorespiration, catalyzing the oxidation of glycolate to glyoxylate with an equal molar amount of H2O2 produced (Foyer et al, 2009). Photorespiration counters the carbon fixation reaction of the Calvin cycle in term of its release of CO2and can account for more than 20% loss of net CO2 assimilation in C3 plants (Peterson, 1983; Sharkey, 1988). Photorespiration is believed to play various roles in plants despite this negative impact. In addition to the ancillary metabolic role in converting 2-phosphoglycolate to 3-phosphoglycerate as a carbon recovery system (Boldt et al, 2005), photorespiration has been suggested to play a role in.
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