Abstract
The improvement of a plant's tolerance to drought is a major endeavor in agriculture. Polyploid plants often exhibit enhanced stress tolerance relative to their diploid progenitor, but the matching stress tolerance is still little understood. Own-rooted stem cuttings of mulberry (Morus alba L.) cultivar Shinichinose (2n = 2x = 28) and Shaansang-305 (2n = 3x = 42) were used in this study, of which the latter (triploid) has more production and application purposes. The responses of triploid Shaansang-305 and diploid progenitor ShinIchinose under drought stress were compared through an investigation of their physiological traits, RNA-seq, and secondary metabolome analysis. The results showed that the triploid exhibited an augmented abscisic acid (ABA) content and a better stress tolerance phenotype under severe drought stress. Further, in the triploid plant some genes (TSPO, NCED3, and LOC21398866) and ATG gene related to ABA signaling showed significantly upregulated expression. Interestingly, the triploid accumulated higher levels of RWC and SOD activity, as well as more wax on the leaf surface, but with less reductive flavonoid than in diploid. Our results suggest triploid plants may better adapt to with drought events. Furthermore, the flavonoid metabolism involved in drought resistance identified here may be of great value to medicinal usage of mulberry. The findings presented here could have substantial implications for future studies of crop breeding.
Highlights
Polyploidization has occurred numerous times throughout the evolutionary history of all plants and dramatically improved the successful adaptation of an extensive range of angiosperms to different habitats (Van de Peer et al, 2017; Chen et al, 2018; Wu et al, 2020)
Superoxide dismutase (SOD) levels continued to increase under severe drought stress in the triploid, yet there was no significant change in the diploid (Figure 1F)
According to the correlations between the modules and samples, we found that the diploid and triploid samples were correlated to some extent with the salmon module: generally, genes of this module were highly expressed in the samples (c: SD-2X-9, d: SD-2X-15, g: FIGURE 3 | Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of the DEGs on the 9th day and Weighted gene co-expression network analysis (WGCNA) of differentially expressed genes (DEGs) identified in drought treated and control over three sampling time points (5, 9, and 15 days) during drought stress. (A,B) The 20 most significantly enriched KEGG pathways for DEGs in response to drought after nine days in diploids (2X) (A) and triploids (3X) (B). (C) Salmon module eigengene expression values across all the samples
Summary
Polyploidization has occurred numerous times throughout the evolutionary history of all plants and dramatically improved the successful adaptation of an extensive range of angiosperms to different habitats (Van de Peer et al, 2017; Chen et al, 2018; Wu et al, 2020). Plenty of evidence on the molecular mechanism of polyploidy resistant to drought stress in various species has been reported. The drought stress response of polyploidy plants relative to their diploid progenitor remains contentious. Based on an admittedly limited number of examined species, autopolyploid may confer better stress tolerance to water deficit, such as in autopolyploid Panicum virgatum L., Dianthus broteri, and tetraploidy Arabidopsis (Del Pozo and Ramirez-Parra, 2014; Lopez-Jurado et al, 2019; Chen et al, 2020). There are relatively few such studies on woody plants, despite their unique and well-known physiological mechanisms for maintaining water balance, such as perennation, woody stem tissue formations, and long-distance transportation of water
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
