The Tomato Ethylene Receptor Gene Leetr1 With Leetr2 Of Features And Their Organizations, Organ-specific Comparative Study

Two transformations from tomato (Lycopersicon esculentum) cultivar Bl with constructs containing the antisense sequence from the receiver domain and 3'-untranslated portion of the tomato ethylene receptor LeETR] and LeETR2 separately under the control of an enhanced cauliflower mosaic virus 35S promoter were obtained previously. The transgenic lines alel and ale2 and its crossed line were identified by PCR, southern blot for NPTII, GUS activity determination and PCR for the target genes, and all the results were positive. Morphological and physiological changes of the transgenic lines, including growth and development, senescence and abscission, fruit ripening, ethylene synthesis, and genes expression of ethylene receptor family, were investigated or analyzed and the following results were presented.I.The alel displayed the following significant characteristics, including shortened and thickened etiolated epicotyl , shortened adult plant in natural light, epinastic petiole growth, shortened inflorescence stem, delayed anthesis and fruit setting, decreased flower number and fruit setting percent, and accelerated senescence of flower and abscission of pedicel and petiole. All of these characteristics suggest that LeETR 1 possibly play important role in regulating tomato vegetative and reproductive growth and development, and organ senescence and abscission. ale2 only displayed shortened epicotyl, accelerated abscission and slightly epinastic petiole, which suggest LeETR2 possibly act in limited tissues.2. When treated with 1-MCP, the coloring of alel fruit was delayed slightly. Upon exposure to exogenous ethylene, it was accelerated to some extent, suggesting that the response of alel fruit to ethylene and ethylene inhibition was enhanced, alel fruit displayed slightly accelerated increasing of polygalacturonase activity and decreasing of firmness, which suggest that LeETR] possibly plays some role in regulating the firmness changing.3. The ethylene production in transgenic fruit significantly increased. In postharvest fruit of alel and ale2 it was respectively three and five times of Bl at climacteric peak. The ethylene production in alel, and in ale2 and dale was respectively five times and tow times of Bl when the fruits were exposed to exogenous ethylene. The ACC content is significantly higher in transgenic fruit. The increased ethylene is possibly related to the enhancement of ethylene synthesis system.4. The expression pattern of ethylene receptor family genes was studied through ribonuclease protection analysis. In wild type plant, LeETRl, LeETR2 and LeETR4 mRNA didn't display significant variation in different tissues. LeETR3 and LeETR5 mRNA express mainly in fruit and little in other tissues. In alel, LeETRl mRNA in abscission zone, turning and ripening fruit, and LeETR5 mRNA in fruit increased, which suggest that LeETR2 and LeETR5 possibly compensate the loss of LeETRl in specific tissue. In transgenic line, corresponding LeETRl or LeETR2 mRNA were not reduced by antisense inhibition, which suggest that the antisense genes possibly play inhibitive role at post...