Physiological and Proteomic Analyses Reveal Effects of Putrescine-Alleviated Aluminum Toxicity in Rice Roots

The effects of putrescine on improving rice growth under aluminum(Al)toxicity conditions have been previously demonstrated,however,the underlying mechanism remains unclear.In this study,treatment with 50 pmol/L Al significantly decreased rice root growth and whole rice dry weight,inhibited Ca2+uptake,decreased ATP syn thesis,and in creased Al,H2O2 and malon dialdehyde(MDA)con tents,whereas the application of putrescine mitigated these negative effects.Putrescine increased root growth and total dry weight of rice,reduced total Al content,decreased H2O2 and MDA contents by increasing antioxidant enzyme(superoxide dismutase,peroxidase,catalase and glutathione S・transferase)activities,increased Ca2+uptake and energy product!oru Proteomic analyses using data-independent acquisition successfully identified 7934 proteins,and 59 representative proteins exhibiting fold-change values higher than 1.5 were randomly selected.From the results of the proteomic and biochemical analyses,we found that putrescine significantly inhibited ethylene biosynthesis and phosphorus uptake in rice roots,increased pectin methylation,decreased pectin content and apoplastic Al deposit!on in rice roots.Putrescine also alleviated Al toxicity by repairing damaged DNA and increasing the proteins involved in maintaining plasma membra ne integrity and normal cell proliferation.These fin dings improve our understanding of how putrescine affects the rice response to Al toxicity,which will facilitate further studies on environmental protection,crop safety,in novations in rice performance and real-world producti on.