| Bt insect-resistant transgenic plant has already been commercialized. The expression of Bt toxin in certain plant developmental period, certain quantity or certain organ in the transgenic plant is an important study field both in new generation of Bt crops and biosafty of Bt crops. Promoter plays a key role to control foreign gene's expression feature: when, where or how much. Constitutive promoter, which drives the foreign gene expressed in all plant organs and throughout the plant developmental period, is widely used in plant genetic engineering studies now. This may squander the plant nutrient and energy and results in increased metabolism burden of the plant. Sometimes the growth and development of the transgenic plant was influenced. Intending further application in the Bt cotton, this study had analyzed the function of a promoter, which is cotton ADP-ribosylation factor 1 (arfI) gene's promoter, cloned in this lab.In this work, two Cry1A plant expression vectors were constructed: pGBI121.AlBt (vector A) carries cryIA expression box droved by arfl promoter;pGBI35SBtAlBt (vector B) carries two cryIA expression box droved by arfl promoter and CaMV35S promoter respectively. Control vector pGBI121.4AB (vector CK) , which is constructed in the former work, carries cry IA expression box droved by CaMV35S promoter.Plant expression vector A. B and CK were transferred into tobacco plant by Agrobacterium mediated transformation respectively. 231 regeneration tobacco plants were obtained after kanamycin screening. Among them, 68 plants were transformed by vector CK, 61 plants by vector A and 102 plants by vector B. The Bt toxin expression level in different organs was analyzed by ELISA. In tobacco capsula, the average Bt toxin protein expression level of A line and B line was 1.5 times and 2.4 times than CK respectively. In tobacco capsular hull, the toxin expression level of A and B was 1.5 times and 1.9 times compared with CK respectively;In tobacco flower, the toxin expression level of A and B was 1.4 times and 1.5 times compared with CK respectively;In tobacco leaf, the toxin expression level of A and B was 0.3 times and 1.4 times compared with CK respectively .The results showed that the arfI promoter can obviously improve the toxin gene's expression in tobacco capsula, capsular hull and petal compared with CaMV35S promoter, although the toxin expression was lower in leaf. In addition, we found the two promoter has synergy effect in transgenic tobacco.Furthermore, we transferred the vector A, B and CK into upland cotton variety Y18 and P13 by pollen tube pathway transformation method. We obtain T. seed of Y18 and P30 456.89 gram and 2468.58 gram respectively. After kanamycin screening and PCR analysis, 17 Y18 transgenic cotton plants were identified, among them, CK line had 10 plants, A lines had 4 plants and B lines had 3 plants. 32 transgenic cotton plants were selected from P13 transformation seeds, 19 plants were transformed byvector A and 8 plants were transformed by vector B. By ELISA, we analyzed the Bt toxin expression level in transgenic cotton young boll and leaf. The results did not totally confer with the analyzed result that obtained in transgenic tobacco. This illustrated that the insecticidal gene expression situations in cotton was more complicated. However, the data proved that the toxin expression level of A transgenic lines, in which foreign insecticidal gene was droved by arfl promoter, was much higher than CK transgenic line.This study analyzed the expression specificity of arfl promoter both in tobacco and cotton. The results had proved that arfl promoter could drive foreign gene expressed well especially in propagation organs. Therefore, we believe arfl promoter could be applied in the development of new generation Bt cotton, which had better cotton bollworm resistant effect for expressing more Bt toxin in cotton boll.
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