The Role Of Dehydroascorbate In Tobacco Early Flowering Induced By Low-temperature And Dha Signaling Pathways

Temperature is an important circumstance factor of crop growth. If tobacco, a low-temperature sensitive plant, sensed 13-18℃and lasted for one week around the tobacco transplanting period, then the plants will produce normal leaves but flowering with a lower leaf number than normal and often earlier than expected. The early flowering phenomenon results in lower quality and quantity of the harvested tobacco leaves thus reduced farmer's income. Dehydroascorbate (DHA) was found to play a positive role in the process of tobacco flowering induced by low-temperature. So, understanding the role of DHA in floral induction induced by low temperature and DHA signal pathway has the extremely vital role to solving the tobacco early flowering phenomenon.The tobacco cultivars K326 were used in the experiments. Floral primordia occurred earlier than control in tobacco shoot apical meristem (SAM) after treated with 4℃for 7days. When the whole plant or one leaf attached to a tobacco plant were treated at 4℃for one day, DHA contents and expression levels of SOC1and LFY were all increased in SAM of tobacco. To make sure whether DHA act as a positive factor to regulate key genes (SOC1 and LFY) of floral induction, it was used to treat tobacco SAM. Results showed that DHA up-regulate the expression level of SOC1 and LFY in SAM.As a model system, guard cell was always used to research the plant signal transduction. The DHA signal pathway was analyzed with the variation of stoma aperture of tobacco lower epidermis treated with DHA and different inhibitors of MAPK, NADPH oxidase, calcium channel et al. Compared with control and DHA treated epidermal peels, and the stoma closure induced by DHA was reversed by incubation with DHA and different inhibitors of MAPK, NADPH oxidase and PTPase. Addition DHA and cytochalasin B, its absorption inhibitor, get the similar results. It proved that the DHA signaling transmit via H2O2 signaling pathway partly, and via some intracellular pathway probably.To explore whether DHA signaling pathway was involved in the early flowering induced by low temperature, tobacco SAMs were treated with DHA or 4℃and different inhibitors of DHA signaling pathway simultaneously. Results showed that inhibitors reversed the up-regulation of SOC1 and LFY expression level induced by DHA or 4℃. It proved that the signaling pathway of DHA was involved in tobacco early flowering induced by low-temperature.