Transcriptional and physiological analyses identify a regulatory role for hydrogen peroxide in the lignin biosynthesis of copper-stressed rice roots
2015
Liu, Qingquan | Zheng, Li | He, Fei | Zhao, Fang-Jie | Shen, Zhenguo | Zheng, Luqing
AIMS: Induction of lignin biosynthesis is an adaptive response of plants subjected to many abiotic stresses. In this study, we examined the response of lignin biosynthesis to copper (Cu) stress, with a particular focus on the regulatory mechanism. METHODS: We performed a transcriptomic analysis of rice (Oryza sativa L.) roots, and the microarray data on lignin biosynthesis pathway genes were corroborated by quantitative reverse transcription–polymerase chain reaction (qRT-PCR) analysis. Physiological analyses of rice seedlings treated with Cu(II) sulfate (CuSO₄) were used to confirm the relationship between excess Cu and lignin biosynthesis. In addition, we examined the role of hydrogen peroxide (H₂O₂) in Cu-induced lignin biosynthesis through pretreatments with an NADPH oxidase inhibitor (diphenyleneiodonium, DPI) and a H₂O₂scavenger (dimethylthiourea, DMTU). RESULTS: Lignin biosynthesis pathway genes were upregulated under Cu stress. The lignin content of rice roots increased significantly with increasing concentrations and durations of Cu treatment; elevations in root lignin content were correlated with marked inhibitions in root growth. Pretreatments with DPI and DMTU inhibited the activities of Cu-induced lignin polymerization enzymes (peroxidase, POD and laccase, LAC) and lignin accumulation in rice roots. Conversely, exogenous H₂O₂increased the root lignin content. CONCLUSIONS: Rice roots under Cu stress accumulate lignin through enhanced polymerization of lignin monolignol, a mechanism that requires Cu stress induced H₂O₂.
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