Cloning of a cDNA encoding a 3-dehydroquinate synthase from a higher plant, and analysis of the organ-specific and elicitor-induced expression of the corresponding gene

cDNA clones for all enzymes of the prechorismate pathway of higher plants have previously been cloned, with the exception of the second enzyme of the pathway, 3-dehydroquinate synthase. Here we describe the isolation of a cDNA encoding a 3-dehydroquinate synthase from tomato which was identified by complementing a 3-dehydroquinate synthase-deficient Escherichia coli strain with a tomato cDNA library. The deduced amino acid sequence contains a putative N-terminal plastid-specific transit peptide, and the sequence of the mature enzyme resembles those of the corresponding bacterial enzymes more than of the fungal enzymes. Sequence identity was even higher between the tomato and E. coli sequences than between the E. coli and other known bacterial sequences. The abundance of 3-dehydroquinate synthase transcripts differ in the organs of tomato plants analyzed. In cultured tomato cells, the abundance of 3-dehydroquinate synthase transcripts increased 9-fold within 4 to 5 h of elicitor treatment.