Vanillic Acid Mitigates Dehydration Stress Responses in Blueberry Plants

This study investigated whether vanillic acid (VA) mitigated dehydration stress responses in blueberry (Vaccinium corymbosum L.), and analyzed potential mechanisms mediating this activity. We pretreated 2‑year-old blueberry plants with 40 μM VA for two days, and then induced dehydration stress by irrigating with nutrient solution containing 10% (w/v) polyethylene glycol 6000 for two days. VA pretreatment increased the transcript levels of genes encoding eight antioxidant enzymes in leaves, including iron superoxide dismutase, chloroplast copper/zinc superoxide dismutase, cytoplasmic copper/zinc superoxide dismutase, catalase, guaiacol peroxidase, glutathione peroxidase, glutathione reductase, and dehydroascorbate reductase. These increased transcript levels were consistent with enhanced activities of superoxide dismutase and glutathione peroxidase and elevated contents of reduced glutathione and ascorbate. Subjecting the V--A‑treated blueberry to dehydration stress further enhanced expression levels of these genes, compared with the control plants subjected only to dehydration stress, increased the contents of endogenous VA, proline, and soluble sugars, enhanced the relative water content and osmotic potential, and reduced the levels of superoxide anion, hydrogen peroxide, and malondialdehyde. So pretreatment of blueberry with VA reduces lipid peroxidation and mitigates dehydration stress by enhancing the endogenous VA content, activating the expression of antioxidant enzyme genes, and increasing the levels of proline and soluble sugars.