Grafting improves drought tolerance by regulating antioxidant enzyme activities and stress-responsive gene expression in tobacco

• Tobacco scions grafted onto drought-tolerant rootstocks improved drought tolerance.
• Rootstock-grafted plants displayed higher SOD and CAT activities, but less MDA level.
• Rootstock-grafting upregulated expression of stress-responsive genes in tobacco.

Grafting has been used to induce abiotic stress tolerance in horticultural crops recently. However, few studies have come out with the effects of grafting and its possible molecular mechanism under drought conditions in tobacco. In this study, using the drought-tolerant cultivar Nongda202 as a rootstock and the drought-sensitive cultivar K326 as a scion, we exposed non-grafted (K326/K326), self-grafted (K326/K326) and rootstock-grafted (K326/Nongda202) tobacco plants to drought stress over a 12-day period, and investigated their differential physiological and molecular responses to drought stress. Our results showed that drought-induced inhibition of growth was significantly alleviated in rootstock-grafted plants, as was evidenced by the physiological indexes, such as much higher SOD and CAT activities, higher levels of proline accumulation and lower levels of lipid peroxidation. Further expression analysis by real-time PCR indicated that rootstock-grafting affected transcripts of stress-responsive genes NtAREB, NtCDPK2, NtLEA5 and NtERD10C in a prompt and lasting manner. Together, these results demonstrated that grafting with rootstock genotypes tolerant to drought could improve drought stress tolerance in tobacco by regulating antioxidant enzyme activities and stress-responsive gene expression. This study will facilitate to broaden our understanding of the regulatory machinery of grafting, and will accelerate potential application of the grafting technique in improving biotic and abiotic stress tolerance in crop plants.