Cinnamic acid 4-hydroxylase (C4H), a member of the cytochrome P450 monooxygenase superfamily, plays a central role in phenylpropanoid metabolism and lignin biosynthesis and possibly anchors a phenylpropanoid enzyme complex to the endoplasmic reticulum (ER). high degree of identity in their deduced amino acid sequence (>85%) with the exception of two divergent isoforms from maize and French bean, which show only approximately 60% identity to other genes (Potter et al., 1995; Nedelkina et al., 1999). The catalytic identity of several cloned C4H cDNAs has been confirmed by heterologous expression in yeast (Urban et al., 1994; Koopmann et al., 1999), in insect cells (Mizutani et al., 1997), or in as a CPR-fusion protein (Hotze et al., 1995). Regulation of expression has been investigated in various plants and cell-culture systems. Transcriptional regulation buy 1032823-75-8 seems to be a major mechanism for control of expression during development and in response to external stimuli as it is for and expression by light, buy 1032823-75-8 wounding, elicitors, and pathogen infection has been documented in many plants (Chapple, 1998). Developmentally controlled manifestation in parsley can be correlated with lignification and additional sites of energetic phenylpropanoid rate of metabolism (Koopmann et al., 1999), as well as the Arabidopsis promoter offers been proven to designate a design of temporal and spatial gene buy 1032823-75-8 manifestation correlated with lignification of bolting stems (Bell-Lelong et al., 1997). Since promoter areas talk about common cis-elements with those of and (Logemann et al., 1995; Bell-Lelong et al., 1997; Mizutani et al., 1997), the assumption is that’s under similar regulatory control generally. This would become consistent with reviews of cells- and cell-type particular colocalization of PAL, C4H, and 4CL mRNA and GNG7 proteins (Koopmann et al., 1999). By expansion of this idea, it’s been hypothesized these enzymes could be physically connected with one another in structured multi-enzyme complexes (MECs). Metabolite channeling from l-Phe to varieties (poplars, cottonwoods, and aspens) offer versions for molecular and hereditary research of tree biology for their little genomes, simple vegetative propagation, change systems, and hereditary assets (Sterky et al., 1998, and referrals therein), and an indicated sequence label (EST) genome task continues to be initiated in (Sterky et al., 1998). Phenylpropanoid genes encoding and also have been cloned and characterized from many varieties (Subramaniam et al., 1993; Osakabe et al., 1995; Allina et al., 1998; Hu et al., 1998). Aswell, sequences have already been reported from two varieties (Ge and Chiang, 1996; Kawai et al., 1996), and it is reported to be encoded by a small gene family in (Kawai et al., 1996). To better understand the catalytic and structural role of C4H in woody plants, we isolated a C4H cDNA from a hybrid, profiled its expression relative to other phenylpropanoid genes, and demonstrated its catalytic activity by expression in yeast. Using a C4H::GFP fusion, we show for the first time that C4H is predominantly localized to ER in planta, consistent with its postulated role in anchoring phenylpropanoid enzyme MECs to the ER. RESULTS Isolation and Characterization of buy 1032823-75-8 a Poplar C4H cDNA Use of a heterologous C4H probe enabled us to retrieve a number of putative C4H cDNA clones from a hybrid poplar cDNA library. Sequence analysis showed that one cDNA, C4H-550 (GenBank accession no. “type”:”entrez-nucleotide”,”attrs”:”text”:”AF302495″,”term_id”:”12276036″,”term_text”:”AF302495″AF302495), contained the complete coding sequence for a putative C4H protein. Comparison of this clone to two additional partially sequenced clones across their 5 coding and 3-untranslated regions revealed that each clone had a unique sequence. At the nucleotide level, the coding regions showed approximately 90% identity, whereas the 3-untranslated regions showed approximately 80% to 90% identity to each other. Most of the differences occurred at the third nucleotide position of codons in the coding regions, and as a result, these clones were >96% identical in their deduced amino acid sequences (data not shown). This heterogeneity could be due either to allelic variation between genes from two parental genomes in the H11 hybrid or to the presence of multiple highly similar gene.