Nitrogen fixation gene island suitable for expressing in prokaryotic and eukaryotic systems
Provided is a nitrogen fixation gene island suitable for expressing in prokaryotic and eukaryotic systems, wherein the prokaryotic nitrogen fixation genes are modified using T7 promoters to make them suitable for eukaryotic expression.
1. An expression island comprising multiple prokaryotic nitrogen fixation genes and multiple T7 promoters but does not contain a natural promoter of said prokaryotic genes for nitrogen fixation, wherein each T7 promoter regulates one or more of said genes, and wherein the relative strength of the natural promoter and that of the T7 promoter are around the same level, wherein said multiple T7 promoters comprise T7M6, and said genes comprise nifF, nifB, and nifQ.
2. The expression island of claim 1 , wherein said multiple T7 promoters further comprise the promoters selected from the group consisting of T7wt, T7M4, T7M5, T7M7, T7M8, and T7 variant that has promoter activity.
3. The expression island of claim 1 , wherein said multiple genes are presented in the form of natural operons.
4. A plasmid comprising the expression island of claim 1 .
5. An expression system comprising the plasmid of claim 4 and a multicopy plasmid comprising T7 RNA polymerase genes.
6. A cell comprising the expression island of claim 1 .
7. The expression island of claim 3 , wherein one operon contains a restriction site different from other operons.
8. The expression island of claim 1 , wherein said genes further comprise the genes selected from the group consisting of nifJ, nifH, nifD, nifK, nifE, nifN, nifU, nifS, nifV, nifM, nifX and NifY.
9. The plasmid of claim 4 , wherein said plasmid is a multicopy plasmid.
10. A cell comprising the plasmid of claim 4 .
11. A cell comprising the expression system of claim 5 .
12. The expression island of claim 7 , wherein the operons comprise T7M6+nifF and T7M6+nifBQ.
13. The expression island of claim 12 , wherein the expression island further comprises the operons selected from the group consisting of T7wt+nifJ, T7wt+nifHDKY, T7M5+nifENX, T7M5+nifUSVM.