Response of Phenylethanoid Systems to Photoperiod in Rose Flower Petals

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We have found that the endogenous levels of molecules, such as enzymes and volatile components, involved in the scent emission were changed by the photoperiod. In this research we focused our research to elucidate the biosynthetic pathways of 2-phenylethanol (2PE) and its β-D-glucopyranoside (2PEG). We also tried to clarify the phenylethanoid systems, such as volatile compounds, their glucosides, enzymes, and the genes, being involved in the scent emission from the flower petals of roses.1. Identification of PLP-dependent aromatic amino acid decarboxylase (AADC) and phenvlacetaldehvde reductase. (PAR)Phenylacetaldehyde (PAId), the direct precursor o 2PE, was produced from L-phenylalanine (Phe). PLP-dependent AADC directly produced PAId together with NH_3 and H_2O_2 under aerobic conditions. The activity of rose petal AADC to yield PAId showed nine times higher activity toward L-Phe than toward its D-isomer. PAId was subsequently converted to 2PE by the action of PAR. The PAR showed spe … More cificity toward several volatile aldehydes, whereas ketone groups of the volatile compounds were not reduced at all.2. Isolation and characterization of β-glucosidase, involved in the hydrolysis of 2PEG to produce 2PE.We have successfully isolated β-glucosidase from the flower petals of roses. The partial peptide sequences were characterized by TOF-MS/MS after the partial hydrolysis of the enzyme. Based on the analysis of the sequences, we have cloned the full-length β-glucosidase using the Rose EST sequence, and expressed the gene in the insects cell systems. The rose petal β-glucosidase showed a specificity toward β-glucopyranoside of several plant volatile compounds, whereas the activity toward the α-glucopyranosides, galactopyranosides, xylopyranosides, were quite low.3. Response of 2PE emission toward Photoperiod and the effects of LED-colorsAlthough we could trace the change in the 2PE emission from the flowers of intact rose plants throughout 12L-12D-photoperioc, the amount of 2PE emitted from each flower was fluctuated. Thus we have developed the new methods to trace the change in the 2PE emission by using flower petals of roses. The diurnal emission of 2PE was observed for at least three days. The similar patter was observed when Red LED was used, although blue and green LED did not have such effects. As a continuing research, the regulation of 2PE emission will be examined based on mRNA expression, enzymatic activity and change in the levels of several small molecules. involved in the phenylethanoid systems. Less