Multiple Insights Reveal Lignin-Mediated Cadmium Detoxification in Rice (Oryza Sativa)

Abstract

Cadmium (Cd) is readily absorbed by rice and enters the food chain, posing a health risk to humans. A better understanding of the mechanisms of the Cd-induced response in rice will help in developing solutions for decreasing Cd uptake in rice. Therefore, this research tried to uncover the detoxification mechanisms of rice in response to Cd through physiological, transcriptomic and molecular approaches. The results showed that Cd stress restricted rice growth, led to Cd accumulation, H2O2 production and resulted cell death. Transcriptomic sequencing revealed glutathione and phenylpropanoid were the important metabolism pathways under Cd treatment. Physiological studies showed that antioxidant enzyme activities, glutathione and lignin contents were significantly increased under Cd stress. In response to Cd stress, q-PCR results showed that lignin and glutathione biosynthesis related genes were up-regulated, whereas, metal transporter genes were down-regulated. Further pot experiment using rice cultivars with increased and decreased lignin content confirmed the causative link between increased lignin and reduced Cd in rice. This study provides a comprehensive understanding of lignin-mediated detoxification mechanism in rice under Cd stress and explains the function of lignin in production of low-Cd rice to ensure human health and food safety.

Keywords: heavy metal, phenylpropane, Transcriptome, cell wall, Glutathione