Poster: Cell Walls

Abs # 1276: Regulatory sequences distinguish the physiological function of multiple cinnamate 4-hydroxylase genes in quaking aspen

Presenter:	Lu, Shan-Fa , slu@unity.ncsu.edu
Authors	Lu, Shan-Fa  (A)   Zhou, Yihua  (A)   Li, Laigeng  (A)   Chiang, Vincent L.  (A)
Affiliations:	(A): North Carolina State University

Cinnamate 4-hydroxylase (C4H) catalyzes the conversion of cinnamate to 4-hydroxy-cinnamate, a key step of metabolic pathways for phenylpropanoid biosynthesis, such as lignin, flavonoids, tannin, and others. To understand how C4H gene is associated with various phenylpropanoid metabolisms, 4 C4H cDNAs (PtC4H) were isolated from Populus tremuloides developing xylem tissue. The coding regions of these cDNAs were highly homologous to each other, but their 5’- and 3’-non-coding regions displayed significantly diverse sequences. The deduced protein sequences of these 4 cDNAs were almost identical except a few variations of amino acidic residues.And these variations were verified being inconsequential for the biochemical performance when the enzymatic activities of their yeast recombinant protein were examined. The expression of PtC4Hs was detected in various tissues, including developing xylem, phloem, epidermis, leaf, and adaxial cells. However, the results of quantitative RT-PCR amplified by the specific non-coding region primers indicated distinct expression patterns for various PtC4H. Furthermore, genomic cloning analysis revealed evident sequential differences among the cognate promoter fragments. Promoter activity analyses demonstrated that different PtC4H promoters functioned in a variety of specific tissue preferences as determined through a GUS report system. All together, this suggested that the translation products of 4 PtC4H genes might have the same biochemical activity but physiologically function in different metabolic processes, for which the regulatory sequences instead of the coding region played a critical role in guiding specific expression of various PtC4Hs. The profiles of 4 PtC4H gene expressions and their promoter function will be discussed in detail.