Kim Myoung K, Jeon Jae-Heung, Fujita Masayuki, Davin Laurence B, Lewis Norman G
Institute of Biological Chemistry, Washington State University, Pullman 99164-6340, USA.
Plant Mol Biol. 2002 May;49(2):199-214. doi: 10.1023/a:1014940930703.
The isolation and characterization of a multigene family of the first class of dirigent proteins (namely that mainly involved in 8-8' coupling leading to (+)-pinoresinol in this case) is reported, this comprising of nine western red cedar (Thuja plicata) DIRIGENT genes (DIR1-9) of 72-99.5% identity to each other. Their corresponding cDNA clones had coding regions for 180-183 amino acids with each having a predicted molecular mass of ca. 20 kDa including the signal peptide. Real time-PCR established that the DIRIGENT isovariants were differentially expressed during growth and development of T. plicata (P < 0.05). The phylogenetic relationships and the rates and patterns of nucleotide substitution suggest that the DIRIGENT gene may have evolved via paralogous expansion at an early stage of vascular plant diversification. Thereafter, western red cedar paralogues have maintained an high homogeneity presumably via a concerted evolutionary mode. This, in turn, is assumed to be the driving force for the differential formation of 8-8'-linked pinoresinol derived (poly)lignans in the needles, stems, bark and branches, as well as for massive accumulation of 8-8'-linked plicatic acid-derived (poly)lignans in heartwood.
本文报道了第一类 dirigent 蛋白多基因家族的分离与鉴定（在本案例中，该家族主要参与导致（+）-松脂醇的 8-8' 偶联反应），该家族由九个西部红雪松（Thuja plicata）DIRIGENT 基因（DIR1-9）组成，它们彼此之间的同一性为 72-99.5%。其相应的 cDNA 克隆具有 180-183 个氨基酸的编码区，每个编码区预测的分子量约为 20 kDa，包括信号肽。实时定量 PCR 结果表明，DIRIGENT 同工变体在西部红雪松的生长发育过程中差异表达（P < 0.05）。系统发育关系以及核苷酸替换的速率和模式表明，DIRIGENT 基因可能在维管植物多样化的早期阶段通过旁系同源基因扩增而进化。此后，西部红雪松的旁系同源基因可能通过协同进化模式保持了高度的同质性。反过来，这被认为是针叶、茎、树皮和树枝中 8-8'-连接的松脂醇衍生（多）木脂素差异形成的驱动力，也是心材中 8-8'-连接的plicatic 酸衍生（多）木脂素大量积累的驱动力。
