HIGH-LEVEL EXPRESSION OF A MITOCHONDRIAL ORF-522 GENE FROM THE MALE-STERILE SUNFLOWER IS LETHAL TO ESCHERICHIA-COLI

To clarify the biological and biochemical functions of the mitochondri al orf 522 gene from a cytoplasmic male-sterile line of the sunflower, we cloned the entire orf 522 gene in-frame into an expression vector (pMAL-c2) of E. coli to obtain a large amount of protein, However, we observed that E. coli harboring a fusion plasmid with the orf 522 gene failed to produce colonies on plates containing 0.3 mM IPTG, an induc er of the p tac promoter of the plasmid, The growth curve of the E. co li also showed that the growth of the cells harboring the fusion plasm id was drastically suppressed immediately after the addition of IPTG t o the medium, SDS-PAGE and western blots of E. coli lysate showed that a 62 kDa protein was expressed only in the cells with a fusion plasmi d after induction with IPTG, These results indicated that the high-lev el expression of mitochondrial orf 522 gene from the male-sterile sunf lower was lethal to E. coli.