Abstract
BACKGROUND: Nicotine exhibits positive heterosis, and through its utilization, new tobacco varieties with ideal nicotine content have been bred. However, the potential mechanism underlying the increased transport and nicotine accumulation capacity in hybrids remain poorly understood. RESULTS: The purpose of this study was to reveal the regulatory role of the key gene NtGSTU10, which was identified during the early stages of nicotine heterosis. NtGSTU10-over expression lines were created through genetic transformation, and the nicotinic content, transport coefficient, and heterosis of NtGSTU10-over expression lines and wild-type tobacco plants were compared. The results suggested that the nicotine content in the leaves of V×OB7 (The over expression hybrids were produced by crossing Va116 as the female parent with OB7 as the male parent.) and V×OB12 (The over expression hybrids were produced by crossing Va116 as the female parent with OB12 as the male parent.) was significantly higher than that of the wild-type hybrid (V×B). Compared to the V×B, the nicotine transport coefficients of V×OB7 and V×OB12 were significantly increased by 39.50% and 40.67%, respectively; and nicotine heterosis was significantly increased by 120.07% and 127.59%, respectively. Further analysis showed that overexpression of the NtGSTU10 gene could result in up-regulated expression of genes related to nicotine synthesis (AOC, QS, ODC, and PAO) and transport (ABCB1, ABCC1, and ABCC2), as well as down-regulation of negative regulatory factors (ERF1, ETR, and JAZ). CONCLUSIONS: The results indicated that overexpression of the NtGSTU10 gene promotes the synthesis and transport metabolism of nicotine in tobacco, positively contributing to increased nicotine content in hybrids. The research findings provide a molecular basis for regulating the nicotine transport and accumulation in hybrids, and also provide genetic resources for the targeted cultivation of new tobacco varieties with suitable nicotine content.