Dear Editor,Photorespiration reduces plant carbon assimilation by an estimated 25％-50％ of net CO2 assimilation in typical C3 plants (Roussel and Igamberdiev,2011).It results from the oxygenase activity of Rubisco giving rise to phosphoglycolate.Subsequent photorespiratory metabolism involves decarboxylation of glycine in the mitochondrion and reduction of hydroxypyruvate,usually assumed to occur in the peroxisome.Recent research in Arabidopsis has highlighted possible alteative sites of hydroxypyruvate reductase (HPR)activity (Figure 1A).In addition to the accepted reduction by peroxisomal HPR1,Timm et al.