MacKay J J, Liu W, Whetten R, Sederoff R R, O'Malley D M
Department of Genetics, North Carolina State University, Raleigh 27695-8008, USA.
Mol Gen Genet. 1995 Jun 10;247(5):537-45. doi: 10.1007/BF00290344.
The gene encoding the monolignol biosynthetic enzyme cinnamyl alcohol dehydrogenase (CAD, E.C. 1.1.1.195) can be expressed in response to different developmental and environmental cues. Control of Cad gene expression could involve either differential regulation of more than one Cad gene or, alternatively combinatorial regulation of a single Cad gene. In loblolly pine (Pinus taeda L.), we found several electrophoretic variants (allozymes) of CAD and a high level of heterozygosity (he = 0.46). Analysis of inheritance patterns of pine CAD allozymes gave segregation ratios that were consistent with Mendelian expectations for a single functional gene. The identity of the full-length Cad cDNA sequence was confirmed by alignment with peptide sequences obtained from purified active enzyme and by extensive similarity to Cad sequences from other species. Southern blot analysis of genomic DNA using the Cad cDNA as a hybridization probe gave simple patterns, consistent with our interpretation that pine Cad is a single-copy gene. Phylogenetic analysis and evolution rate estimates showed that Cad sequences are diverging less rapidly in the gymnosperms than in the angiosperms. The Cad mRNA was present in both lignifying tissues and a non lignifying tissue (the megagametophyte) of pine. The presence of a single gene suggests that different regulatory mechanisms for a single Cad gene, rather than differential regulation of several genes, can account for its expression in response to different cues.
编码单木质醇生物合成酶肉桂醇脱氢酶（CAD，E.C. 1.1.1.195）的基因可响应不同的发育和环境信号而表达。Cad基因表达的调控可能涉及多个Cad基因的差异调控，或者单个Cad基因的组合调控。在火炬松（Pinus taeda L.）中，我们发现了CAD的几种电泳变体（同工酶）以及高水平的杂合性（he = 0.46）。对松树CAD同工酶遗传模式的分析得出的分离比与单个功能基因的孟德尔预期一致。通过与从纯化的活性酶获得的肽序列比对以及与其他物种的Cad序列的广泛相似性，证实了全长Cad cDNA序列的身份。使用Cad cDNA作为杂交探针对基因组DNA进行Southern印迹分析得到简单的模式，这与我们认为松树Cad是单拷贝基因的解释一致。系统发育分析和进化速率估计表明，Cad序列在裸子植物中的分化速度比被子植物中的分化速度慢。Cad mRNA存在于松树的木质化组织和非木质化组织（大配子体）中。单个基因的存在表明，单个Cad基因的不同调控机制而非几个基因的差异调控，可以解释其对不同信号的响应表达。
