| Abscisic acid (ABA) is a plant hormone that plays major roles in the control of plant growth and development including seed maturation, plant senescence, and in the response to various environmental stresses such as drought, cold, and salinity. One of the key genes involved in ABA synthesis, ZEP encodes for zeaxanthin epoxidase, catalyses the epoxidation of zeaxanthin and antheraxanthin to all-trans-violaxanthin, which occurs in plastids. Before our study, we have possessed of transgenic tobaccos, which contain a complete ThZEP cDNA (cloned from Thellungiella halophila) in a sense or antisense orientation. Firstly, an attempt has been made here to study the phenotype of transgenic tobacco in stress environment. Secondly depending on an established genetic transformation system of Zhanhua winter jujube, transgenic plants were obtained by introducing the ThZEP in a sense and antisense orientation.Putative transgenic plantlets were analyzed by PCR and Southern blot. Then, some of transgenic plantlets were confirmed by Northern blotting, which expression of target gene was confirmed.Responding to drought stress, ABA regulates stomatal aperture by inhibiting stomatal opening and inducing stomatal closure in guard cells. A polyethylene glycol solution is expected to mimic the effect of water deficit stress and increase the ABA concentration of plants. Fully expanded leaves of transgenic tobaccos were detached, and the leaves were sliced into 1cm~2 strips with a sharp razor blade. Then, the leaf slices were incubated in 10% PEG6000 solution for about 2 h. There was not obvious difference on stomatal aperture between ten transgenic tobaccos and wild-type plants except for line +1. The result attested again that in leaves the transcript levels of ZEP gene did not response to stress. To investigate the change in ABA content and the difference on symptom of transgenic tobaccos, the transgenic plants and wild-type plants were simultaneously treated with PEG6000 solution. Under normal growth... |
