4.1 Drought adaptation differences of S. krylovii among different regions
In this study, the factor of seed source of region showed significant effects on growth and physiological traits (Table 2), which was consistent with the previous studies (Klein & Mitchell, 2024). In addition, under the heavy drought treatment, unique enriched pathways were found of individuals from each region.
For individuals from the eastern region under heavy drought treatment, specific KEGG enriched pathways included thiamine metabolism, fructose and mannose metabolism (Fig. 2c), and these metabolism pathways are found to be related to drought tolerance in several researches. Li et al. (2022) have shown that exogenous application of thiamine can enhance plant stress tolerance by activating stress-responsive genes and calcium signal transduction. Ye et al. (2020) have found that Pterocarya stenoptera initiates the thiamine metabolism pathway under drier air stress condition using 6-month-old seedlings. You et al. (2019) have shown that genes for fructose and mannose metabolism are up-regulated in drought-tolerant sesame to cope with stress condition.
For the individuals from the middle region under heavy drought treatment, specific KEGG enriched pathways included basal transcription factors, and circadian rhythm-plant (Fig. 2f). Circadian rhythm-plant pathway is common for species under the drought condition (Wang et al., 2021). Transcription factors pathway is an important class of regulatory proteins that plays important roles in regulatory networks and signaling pathways of plant development and abiotic stresses (Yang et al., 2017); however, the basal transcription factors pathway related to drought adaptation was not common in previous studies. Therefore, more specific researches on transcription factors pathway are needed for S. krylovii in the future.
For the individuals from the western region under heavy drought treatment, specific KEGG enriched pathways included protein processing in endoplasmic reticulum, ubiquitin mediated proteolysis (Fig. 2i). This finding was consistent with the previous studies. Moon et al. (2018) have found that the drought tolerance mechanisms of the drought-tolerant potato (Solanum tuberosum L.) are related to protein processing in the endoplasmic reticulum as well as the photosynthetic-antenna protein. Zhang et al. (2021) have shown that endoplasmic reticulum and capacity of ubiquitin-mediated proteolysis pathways play important roles in gene expression of Bt cotton under high-temperature and water deficit stress conditions.