Glycolate oxidase-dependent H2O2 production regulates IAA biosynthesis in rice
Xiangyang Li, Mengmeng Liao, Jiayu Huang, Zheng Xu, Zhanqiao Lin, Nenghui Ye, Zhisheng Zhang, Xinxiang Peng
Abstract
Abstract Background Glycolate oxidase (GLO) is not only a key enzyme in photorespiration but also a major engine for H 2 O 2 production in plants. Catalase (CAT)-dependent H 2 O 2 decomposition has been previously reported to be involved in the regulation of IAA biosynthesis. However, it is still not known which mechanism contributed to the H 2 O 2 production in IAA regulation. Results In this study, we found that in glo mutants of rice, as H 2 O 2 levels decreased IAA contents significantly increased, whereas high CO 2 abolished the difference in H 2 O 2 and IAA contents between glo mutants and WT. Further analyses showed that tryptophan (Trp, the precursor for IAA biosynthesis in the Trp-dependent biosynthetic pathway) also accumulated due to increased tryptophan synthetase β (TSB) activity. Moreover, expression of the genes involved in Trp-dependent IAA biosynthesis and IBA to IAA conversion were correspondingly up-regulated, further implicating that both pathways contribute to IAA biosynthesis as mediated by the GLO-dependent production of H 2 O 2 . Conclusion We investigated the function of GLO in IAA signaling in different levels from transcription, enzyme activities to metabolic levels. The results suggest that GLO-dependent H 2 O 2 signaling, essentially via photorespiration, confers regulation over IAA biosynthesis in rice plants.