Simeng Wan,Weiwei Wu,Chunlei Ou,Ying Cao,Xinyun Guo,Hua Liu,Lihua Yao,Hu Su
Copper treatment can lead to the accumulation of reactive oxygen species, alter the cellular redox state in plants, and trigger plant adaptive mechanisms such as changes in gene expression and shifts in secondary metabolism. We investigated the effects of copper treatment on the redox state of Scutellaria baicalensis Georgi, characterized by glutathione (GSH) and oxidized glutathione (GSSG) levels. We also determined the concentrations of baicalin and baicalein, and analyzed the correlation between the redox state and these metabolites. Moreover, we analyzed the activity of glutathione reductase (GR, EC 1.6.4.2) and the expression levels of GR, phenylalanine ammonia lyase (PAL, EC 4.3.1.5) and isochorismate synthase (ICS, EC 5.4.4.2) genes. Results indicated that copper treatment increased GSH concentration at 24 and 48h, and the ratio of GSH:GSSG, and upregulated GR expression. While the baicalin concentration showed a non-significant increase at 24h and 72h, baicalein exhibited a significant decrease at 48h and 72h. The two key genes in the salicylic acid pathway, PAL and ICS, exhibited opposite trends at 24 and 48h after copper treatment, followed by significant decreases in both PAL and ICS at 72h. Our results suggest that plants can mitigate the toxic effects of copper through increasing GSH biosynthesis. Baicalin and baicalein showed varying accumulation patterns in S. baicalensis subjected to different copper treatments.
Severe marine pollution caused by excessive copper (Cu) has resulted in a great threat to marine biosystems. Gracilariopsis lemaneiformis , the main economically important cultivated macroalgal species of coastal China, is affected by Cu. 1-Aminocyclopropane-1-carboxylic acid (ACC), the direct precursor of ethylene, acts as a potential signaling molecule for plants to defend against heavy metal stress. In the present study, the role of ACC in alleviating Cu stress in G. lemaneiformis was explored by measuring physiological indicators and by performing a comparative transcriptome analysis. Excess Cu reduced photosynthetic rates and relative growth rates, increased Cu accumulation and malondialdehyde levels and induced the antioxidant system in G. lemaneiformis . ACC was found to inhibit the expression of genes encoding Cu transport proteins , greatly decrease Cu accumulation and MDA contents and relieve the inhibition of G. lemaneiformis growth caused by Cu stress. In addition, the expression of most antioxidant synthesis-related genes encoding SOD and APX was downregulated by ACC, and the activity of antioxidant enzymes was reduced. Moreover, ACC stimulated jasmonate acid (JA) synthesis to increase endogenous JA contents and activated pathways related to translation, photosynthesis, and nitrogen metabolism , while ACC did not stimulate the expression of genes involved in ethylene signaling pathways. These findings provide insight into the molecular mechanisms of Cu stress resistance in G. lemaneiformis and benefit the breeding and cultivation of G. lemaneiformis .
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