Physiological and transcriptomic investigation of low pH-mediated salt stress alleviation in ginger (Zingiber officinale Rosc.)

Low pH is effective in minimizing salt stress-induced injury to ginger. However, the mechanism of low pH to alleviate salt stress injury to ginger remains unclear. Therefore, this study aimed to investigate the growth and physicochemical properties of ginger under salt stress by treating ginger with different pH (pH 4, 6), and to comparatively analyze the transcriptome of ginger root system under low pH salt stress. Low pH increased the activities of antioxidant enzymes and the contents of soluble sugars, trehalose and abscisic acid. Comparative transcriptome analysis showed that low pH up-regulated abscisic acid synthesis genes and down-regulated catabolism genes in salt-stressed ginger, resulting in an increase in ABA content in ginger roots. Furthermore, it was found that low pH reduced sodium ion content and increased potassium ion content by up-regulating the expression of ion transporter protein genes in ginger roots under salt stress. Additionally, a potential regulatory network of hormone signaling, ABA, antioxidant enzymes and ion transporters with transcription factors was constructed. In conclusion, the results of this study provide a fundamental theory for the mechanism of low pH to alleviate salt stress in ginger, and provide candidate genes for molecular breeding of salt-tolerant ginger.