Effect of Environmental Stresses on Physiophytochemical Responses and Expressional Profiling Analysis of Flavone C-Glycoside-Associated Genes in Three Bamboo Species

Bamboo, valued for its sustainability and versatility, holds potential in various domains, including food and medicine, due to its abundance of antioxidant compounds such as flavone C-glycosides (FCG) found in bamboo leaf extracts. However, the effects of environmental stress on bamboo growth, phytochemical synthesis, and the genetic regulation of FCG biosynthesis remain unclear. This study investigated the response mechanisms of 3 bamboo genotypes (Pai Sang-Mon, Pai-Liang, and Pai Khao-Lam) under different environmental stresses: Acidity (pH 4.0), heavy metal zinc (200 µM ZnSO4·7H2O), salinity (100 mM NaCl), and water deficit stress over 0, 1, 2, 4, and 8 days. The results indicated that water deficit stress had the most significant impact on growth and photosynthesis, with Pai Khao-Lam and Pai Sang-Mon exhibiting greater drought tolerance than Pai-Liang. Reversed-phase high-performance liquid chromatography (RP-HPLC) analysis revealed diverse responses in phytochemical content. Pai Sang-Mon showed increased caffeic acid and apigenin under salt stress, while Pai-Liang exhibited decreased phytochemical content under acid, zinc, and water deficit stresses. In contrast, Pai Khao-Lam showed elevated p-coumaric acid, chlorogenic acid and vitexin levels under multiple stresses, indicating robust antioxidant capabilities. Gene expression analysis using quantitative real-time PCR indicated differential gene responses among the bamboo genotypes. Pai Sang-Mon showed reduced vitexin levels correlating with decreased expression of the C-glycosyltransferase (CGT1) gene. Pai Khao-Lam exhibited increased expression of the flavanone 2-hydroxylase (F2H) and CGT1 genes under water deficit stress, suggesting a molecular response to maintain cellular homeostasis through phytochemical accumulation. In contrast, Pai-Liang showed increased expression of the sucrose nonfermenting 1-related protein kinase 1 (SnRK1) gene under short-term salt stress, indicating the sensitivity to osmotic stresses. These findings highlight the complex relationship between gene regulation, phytochemical accumulation, and stress tolerance in bamboo, offering valuable insights for breeding bamboo with enhanced stress tolerance and optimizing environmental conditions to maximize phytochemical production in bamboo leaf extracts. HIGHLIGHTS Water deficit stress significantly impacts bamboo growth and photosynthesis. Greater drought tolerance in Pai Khao-Lam and Pai Sang-Mon than in Pai-Liang. Pai Khao-Lam shows increased chlorogenic and p-coumaric acid under multiple stresses. The regulation of CGT1, F2H, and SnRK1 genes differs in bamboo genotypes under stress. GRAPHICAL ABSTRACT