STROMAL AND THYLAKOID-BOUND ASCORBATE PEROXIDASES ARE PRODUCED BY ALTERNATIVE SPLICING IN PUMPKIN

A cDNA encoding stromal ascorbate peroxidase (sAPX) was isolated using poly(A)(+) RNA of pumpkin cotyledons by RT-PCR. The cDNA encodes a po lypeptide with 372 amino acids and shares complete sequence identity w ith pumpkin thylakoid-bound ascorbate peroxidase (tAPX), except for th e deletion of a putative membrane spanning region located in the carbo xy domain of tAPX. Southern blot hybridization and analysis of intron structure indicated that mRNAs for sAPX and tAPX, whose suborganellar localizations in chloroplasts are different, are produced by alternati ve splicing, Immunoblot analysis showed that the accumulation of sAPX and tAPX was differently regulated during germination and subsequent g reening of pumpkin cotyledons. (C) 1997 Federation of European Biochem ical Societies.