T7 RNA Polymerase Is Expressed in Plants in a Nicked but Active Form

T7 RNA polymerase 유전자의 담배식물에서의 발현

We have prepared several chimeric constructs containing the bacteriophage T7 RNA polymerase gene under control of the wound-inducible potato proteinase inhibitor II (pin2) promoter and have transformed Nicotiana tabacum plants with these constructs. Southern blot analyses indicate that either one or two copies of the gene constructs are present in the transgenic plants. Northern blot analyses indicate that mRNA encoding T7 RNA polymerase is expressed in a wound-inducible manner. We purified T7 RNA polymerase and prepared antiserum. This antiserum was used for Western blot analyses to demonstrate that a protein which is cross reactive with T7 RNA polymerase is produced. The molecular mass of this protein is 80 kDa, a size which is consistant with the nicked form of the polymerase as is often seen when expressed in E. coli. RNA polymerase assays were used to indicate that the nicked form of T7 RNA polymerase is active and capable of incorporating labeled nucleotides into transcripts in vitro. Analysis of transgenic plants did indeed show that wound-inducible activation of the T7 RNA polymerase permits the establishment of a genetic system to overexpress genes in plants using T7 RNA polymerase(Received March 20, 1997; accepted May 2, 1997)

박테리오파아지 T7 RNA polymerase 유전자를 식물체내에서 이용할 수 있을지 알아보기 위하여 상처유발인 감자 단백질 분해효소 억제제 유전자의 프로모터에 박테리오파지 T7 RNA polymerase 유전자를 연결시킨 후 담배에 도입시켰다. 형질전환 식물체의 DNA에 대한 Southern hybridization에 의하면 T7 RNA polymerase 유전자가 식물체내에 1-2 copy가 존재하며, Northern hybridization에 의하면 T7 RNA polymerase의 RNA가 상처에 따라 생성되는 것을 확인하였다. 또한 Western hybridization에 의하면 식물체내 T7 RNA polymerase 단백질이 생성되는데 그 크기는 대장균에서 생성되는 단백질 크기와 유사한 80 kDa 이었으며 시험관내에서 전사체에 뉴클레오타이드를 결합시키는 능력이 있음도 확인하였다. 따라서 T7 RNA polymerase 유전자를 이용하여 식물체내에서 원하는 유전자의 발현을 증대시킬 수 있을 것으로 사료된다.