Regulation of metallocarboxypeptidase inhibitor gene expression in tomato

Abstract

Tomato fruits contain a metallocarboxypeptidase inhibitor (MCPI) the sequence of which has already been determined. Here we report the isolation of a tomato cDNA clone that encodes the mature MCPI protein as well as an N-terminal signal peptide for entry into the secretory system and an eight amino acid carboxyterminal extension. MCPI RNA is present at very high levels in anthesis stage ovaries and decreases quite rapidly during fruit development. MCPI protein accumulation reflects the pattern of MCPI RNA accumulation in fruit, consistent with a transcriptional control of MCPI gene activity. In leaves, the levels of MCPI RNA and protein are very low. Wounding of the leaves causes a dramatic (100-fold) increase in steady-state level of MCPI RNA without a concomitant increase in MCPI protein level suggesting a control at the post-transcriptional or translational level of gene expression. Genomic DNA blot hybridization data indicate that MCPI in tomato may be encoded by a single gene.