Study On The Role Of Aquaporin Promoter Of Malus Zumi Mats And Melatonin In Abiotic Stress Response

As one of MIP superfamily members, aquaporins are primarily involved in water and small molecular substances transport in plant. Our previous research indicated aquaporins might participate in abiotic stress response and fruit development. Malus zumi Mats is apple rootstock, which is resistant to salt stress and suitable for molecular research of fruit trees in response to salt stress. The promoter of a MIP member, MzPIP2;1, was further studied to determinie the key cis-acting elements in response to salt, drought and cold stresses. Meanwhile, we compared the promoter sequences of different apple cultivars with different fruit size, to find out the role of TIP2in fruit development. Two genes oAANAT and oHIOMT encoding the key genes in melatonin biosynthesis, were cloned from sheep and transformed into’Micro-Tom’tomato. It significantly increasd the melatonin levels in transgenic lines revealing its synthesis pathway and its function in stress response in plant. The results were as follows:1. The Arabidopsis seedling with GUS drived by MzPIP2;1full-length promoter responded to salt, drought and cold stresses in different pattern in different tissues. Under salt stress, in the young seedlings, full length-promoter and deletion1showed similar response, while deletion2wasn’t inducible. Under drought stress, the result is similar with under salt stress. Under cold stress, deletion2exhibit enhanced response. In the mature plants, the full-length promoter had stronger response than deletion1, and deletion1showed stronger reponse than deletion2. Taken together, it is assumed that the key cis-elements in response to these abiotic stresses were located in deletion2(-948bp--644bp), the cis-elements responding to cold stress might be binded by a suppressor in young seedling. The difference in stress response, between the young seedlings and the mature plants, might be result from other members in the complex binding with the cis-elements.2. The increased melatonin content of transgenic tomatoes overexpressing oAANAT, lose apical dominance. It might result from the substrate competition and reduced IAA level.3. In plant, HIOMT might be the rate-limiting enzyme in melatonin biosynthesis. The increased melatonin content of transgenic tomatoes overexpressing oHIOMT conferred drought tolerance to transgenic plant.