Styrene-dependent induction of the sty operon has been
demonstrated by several groups. Northern blotting and
transcription start site analysis by primer extension in
Pseudomonas sp. strain Y2 revealed that the presence of
styrene was essential for upper pathway gene transcription
[15]. Zennaro and co-workers have reported that L-galactosidase
activity was only detectable in P. £uorescens ST
cells harbouring a plasmid-borne styA promoter: :lacZ fusion
when styrene was present in the medium [34]. Furthermore,
reverse-transcription analysis of total RNA
from P. putida CA-3 grown on various carbon sources
also indicated that there were no detectable mRNA transcripts
from the sty operon in the absence of styrene [19].
Complementation studies performed in E. coli with elements
of the sty operon from both Pseudomonas sp. strainY2 and Pseudomonas sp. strain VLB120, demonstrated
that the StyS and StyR proteins were required for the
styrene-dependent induction of the sty upper pathway
genes [15,41]. It has also been reported in P. putida
CA-3 that transcription of the styrene upper pathway
genes is entirely dependent upon expression of stySR [19]