cDNA encoding (-)-limonene-6-hydroxylase from spearmint and (-)-limonene-3-hydroxylase from peppermint have been isolated and sequenced, and the corresponding amino acid sequences have been determined. Accordingly, isolated DNA sequences are provided which code for the expression of (-)-limonene-6-hydroxylase from spearmint (SEQ ID No:1, from Mentha spicata) and (-)-limonene-3-hydroxylase from peppermint (SEQ ID No:8, from Mentha piperita). In other aspects, replicable recombinant cloning vehicles are provided which code for limonene hydroxylase or for a base sequence sufficiently complementary to at least a portion of the limonene hydroxylase DNA or RNA to enable hybridization therewith (e.g., antisense limonene hydroxylase RNA or fragments of complementary limonene hydroxylase DNA which are useful as polymerase chain reaction primers or as probes for limonene hydroxylase or related genes). In yet other aspects, modified host cells are provided that have been transformed, transfected, infected and/or injected with a recombinant cloning vehicle and/or DNA sequence encoding limonene hydroxylase. Thus, systems and methods are provided for the recombinant expression of limonene hydroxylase that may be used to facilitate the production, isolation and purification of significant quantities of recombinant limonene hydroxylase (or of the primary enzyme products, trans-carveol or trans-isopiperitenol, respectively) for subsequent use, to obtain expression or enhanced expression of limonene hydroxylase in plants to attain enhanced production of trans-carveol or trans-isopiperitenol as a predator or pathogen defense mechanism, or may be otherwise employed for the regulation or expression of limonene hydroxylase or the production of trans-carveol or trans-isopiperitenol.