关键词: 党参, 适度干旱, 多糖组分, 酶活性, 差异基因表达

Abstract:

By investigating metabolite levels， enzyme activities， and gene expression associated with polysaccharide synthesis in the leaves and roots of Codonopsis pilosula under moderate drought conditions， this study amied to reveal the differential regulatory mechanisms governing polysaccharide synthesis in the tissues. During the flowering period， plants were subjected to two treatments：normal moisture（CK， 0% PEG-6000） and moderate drought（DH， 15% PEG-6000）. Samples were collected at 7， 14， and 21 days post-treatment. Using ultraviolet spectrophotometry， high-performance liquid chromatography（HPLC）， and high-throughput sequencing， we quantified the levels of metabolites involved in the polysaccharide synthesis pathway， enzyme activities， and gene expression in root and leaf tissues of C. pilosula. Results indicated that under moderate drought conditions， the levels of upstream metabolites—sucrose， fructose， and glucose—differred between leaves and roots. Specifically， the proportion of glucose increased in roots， whereas it decreased in leaves. Enzyme activities in the polysaccharide synthesis pathway also exhibited distinct tissue-specific responses： sucrase activity increased in both tissues， while the activities of monosaccharide conversion-related enzymes（galE， GAE， UXS1， and UER1） increased in leaves but decreased in roots. Moreover， significant changes in sucrase activity occurred earlier in leaves than in roots. Gene expression analysis further revealed tissue-specific differences in the regulation of polysaccharide synthesis. Among the 10 sucrose invertase regulatory genes， 2 were upregulated and 3 downregulated in leaves， whereas 6 were upregulated and 1 downregulated in roots. For the 14 genes encoding monosaccharide conversion enzymes， 7 were upregulated and 2 downregulated in leaves， compared to 2 upregulated and 5 downregulated in roots. Pearson correlation analysis showed that under moderate drought， the number of genes positively correlated with enzyme activity significantly increased in both tissues. Specifically， gene expression in leaves was positively correlated with monosaccharide conversion enzyme activity， whereas gene expression in roots was positively correlated with sucrose transferase activity. Collectively， moderate drought differentially regulated polysaccharide synthesis in C. pilosula leaves and roots by modulating upstream metabolite levels， sucrose transferase activity， and monosaccharide conversion-related gene expression， thereby controlling tissue-specific polysaccharide synthesis and accumulation.

Key words: Codonopsis pilosula, moderate drought, CPPs component, enzymatic activity, differential genes expression