关键词: 甘薯, 低磷胁迫, 碳点, 转录组, 代谢组

Abstract:

The objective of this study is to explore the effects of foliar sprayed carbon dots (CDs) on the growth and development of sweetpotato seedlings under low phosphorus (P) stress, discovery the key genes that regulate the response of sweetpotato roots to low P stress, analyze the synergistic changes between root metabolites and key genes, and explore the mechanism of CDs alleviating low P stress in sweetpotato. In this study, Shangshu 19 and Xushu 32 were selected as the experimental materials. Three treatments, namely, foliar sprayed with ultra-purewater (CK1 treatment), Salvia miltiorrhiza CDs (CDs treatment) at low P levels (0.01 mmol L^-1 KH₂PO₄), foliar sprayed with ultra-pure water at normal P levels (1 mmol L^-1 KH₂PO₄) (CK2 treatment), were set up to conduct metabolomic and transcriptomic analysis of sweetpotato roots in different treatments, and analysis the changes in biomass and P content in leaves, stems and roots. Results showed that foliar sprayed Salvia miltiorrhiza CDs significantly increased the biomass of leaves, stems, and roots of sweetpotato seedlings under low P stress, increased the P content of roots, and enhanced the low P tolerance of sweetpotato seedlings. Transcriptome analysis revealed that phosphate uptake and transport genes (PHO1, PHT1-4), root configuration regulation genes (ZAT6, ZFP5, PLT5), and inositol phosphate biosynthesis genes (VIP2) play key roles in alleviating low P stress in sweetpotato seedlings. The metabolomic analysis indicated that the relative expression level of inositol phosphate in sweetpotato roots treated with CDs was significantly lower than that in CK1 treatment. These results suggested that foliar spraying CDs can improve the ability of sweetpotato to absorb P by inducing the high affinity P uptake and transport system of sweetpotato and optimizing root configuration, while maintaining P homeostasis by adjusting the P metabolism process in the plant. However, there were differences in the response of different sweetpotato varieties to low P stress mediated by CDs. Compared with CK1 treatment, it was also observed that the expression levels of phosphate esters such as phosphoethanolamine and D-Myo-inositol 4-phosphate in the roots of Shangshu 19 were significantly reduced in CDs treatment, and the expression of citric acid and oxalic acid secreted by the roots of Xushu 32 significantly increased, which can activate insoluble P in the soil and promote P absorption by plants. This may be related to differences in low P tolerance among different sweetpotato varieties. In conclusion, these results can provide scientific support and theoretical basis for establishing efficient regulation theories and new pathways for P nutrition in sweetpotato, and also provide candidate molecular resources for subsequent research on nano CDs to alleviate low P stress in sweetpotato.

Key words: sweetpotato, low P stress, carbon dots, transcriptome, metabolome