A Preliminary Study On BABA-Induced Resistance To Drought Stress And Cadmium Stress In Tobacco

Tobacco, as an important economic crop in China, not only has essential amino acids, but also has high medicinal-valued nicotine. Under the circumstances of adversity, such as the drought and cadmium stress, the tobacco seedlings had a bad growth, which contributed to a poor production and the deceased quality of tobacco leaves. β-Aminobutyric acid (BABA) is an efficient inducer of resistance, which can be against a wide range of biotic and abiotic stresses in plants. But little information was available on alleviating the drought stress and cadmium stress in tobacco. In this experiment, using Yunyan 87 as test material, The present study highlighted the protective role of BABA in alleviating the drought stress and cadmium (Cd) stress in tobacco, and attempted to explore the mechanism through measuring the anti-oxidative molecular content, the anti-oxidative enzyme activities, Osmotic adjustment substances, the metal ion content and also involved the related gene expression.1. The results showed that 5 mmol/L BABA could effectively improve plants’ growth, relative water content (RWC) and the survival rate of tobacco seedlings under drought stress. Meanwhile, the pretreatment of BABA not only increased accumulation of soluble sugar, proline, and soluble protein, but also markedly stimulated the activities of superoxide dismutases (SOD) and peroxidase (POD) compared with drought-stressed alone. Moreover, BABA significantly decreased the malondialdehyde (MDA) level, while enhanced the hydrogen peroxide (H2O2) level. The above evidences revealed that BABA pretreatment helped the plants to combat drought stress by increasing the contents of osmotic adjustment substances, the H2O2 level as well as activating plants’antioxidant system to prevent the cells from drought-induced oxidative damages.2.The present study highlighted the protective role of BABA in alleviating cadmium (Cd) stress in tobacco, and attempted to explore the mechanism through measuring the anti-oxidative molecular content, the activities of antioxidative enzymes, the content of Cd and Fe and also involved the related gene expression. Results indicated that 0.2、0.5 mmol/L BABA could effectively improve plant length, fresh weight and chlorophyll content of tobacco than Cd-treated alone. Meanwhile, the pretreatment of BABA not only increased accumulation of proline, GSH, AsA, soluble sugar and Total phenolic, but also markedly stimulated the activities of superoxide dismutases (SOD), ascorbate peroxidases (APX), peroxidase (POD) and catalases (CAT) compared with Cd treatment alone, thereby indicating the enhancement of the anti-oxidative capacity in the leaves under Cd stress. BABA also counteracted partly Cd toxicity by reducing the H2O2 and MDA contents of Cd-exposed seedlings. Moreover, BABA increased the Cd content in roots, but reduced Cd content in shoots. In addition, the related gene expression indicated that BABA took part in the regulation of the transcript levels of NtIRT1, NtNramp5, NtGSH1, NtPCS1, NtHMA4, NtPDR5b, and NtPCR1.In summary, the above evidences suggested 5 mmo/L BABA pretreatment helped the plants to combat drought stress by increasing the contents of osmotic adjustment substances, the activities of superoxide dismutase and peroxidase, as well as reducing the lipid peroxidation of cell membrane so as to improve the ability to resist drought stress. And still,0.2、0.5 mmo/LBABA pretreatment helped the plants to combat Cd stress by activating plants’ antioxidant system, increasing the contents of osmotic adjustment substances,restricting Cd content in shoot as well as modulating the related gene expression to protect the cells from Cd induced oxidative damages.