Chen Fang, Tobimatsu Yuki, Jackson Lisa, Nakashima Jin, Ralph John, Dixon Richard A
Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK, 73401, USA.
DOE Bioenergy Sciences Center, Oak Ridge, TN, USA.
Plant J. 2013 Jan;73(2):201-11. doi: 10.1111/tpj.12012. Epub 2012 Nov 12.
We have recently described a hitherto unsuspected catechyl lignin polymer (C-lignin) in the seed coats of Vanilla orchid and in cacti of one genus, Melocactus (Chen et al., Proc. Natl. Acad. Sci. USA. 2012, 109, 1772-1777.). We have now determined the lignin types in the seed coats of 130 different cactus species. Lignin in the vegetative tissues of cacti is of the normal guaiacyl/syringyl (G/S) type, but members of most genera within the subfamily Cactoidae possess seed coat lignin of the novel C-type only, which we show is a homopolymer formed by endwise β-O-4-coupling of caffeyl alcohol monomers onto the growing polymer resulting in benzodioxane units. However, the species examined within the genera Coryphantha, Cumarinia, Escobaria and Mammillaria (Cactoideae) mostly had normal G/S lignin in their seeds, as did all six species in the subfamily Opuntioidae that were examined. Seed coat lignin composition is still evolving in the Cactaceae, as seeds of one Mammillaria species (M. lasiacantha) possess only C-lignin, three Escobaria species (E. dasyacantha, E. lloydii and E. zilziana) contain an unusual lignin composed of 5-hydroxyguaiacyl units, the first report of such a polymer that occurs naturally in plants, and seeds of some species contain no lignin at all. We discuss the implications of these findings for the mechanisms that underlie the biosynthesis of these newly discovered lignin types.
我们最近在香草兰的种皮以及一种名为花座球属的仙人掌中描述了一种此前未被怀疑的儿茶酚木质素聚合物（C-木质素）（Chen等人，《美国国家科学院院刊》。2012年，109卷，1772 - 1777页）。我们现在已经确定了130种不同仙人掌物种种皮中的木质素类型。仙人掌营养组织中的木质素是正常的愈创木基/紫丁香基（G/S）型，但仙人掌亚科内大多数属的成员仅具有新型C型种皮木质素，我们发现它是一种由咖啡醇单体通过末端β-O-4偶联到生长中的聚合物上形成的均聚物，从而产生苯并二恶烷单元。然而，在皱棱球属、库马里尼亚属、埃斯科巴瑞亚属和乳突球属（仙人掌亚科）中检测的物种，其种子大多具有正常的G/S木质素，就像所检测的仙人掌科的所有六个物种一样。种皮木质素组成在仙人掌科中仍在不断演变，因为一种乳突球属物种（乳突球属 lasiacantha）的种子仅含有C-木质素，三种埃斯科巴瑞亚属物种（埃斯科巴瑞亚 dasyacantha、埃斯科巴瑞亚 lloydii 和埃斯科巴瑞亚 zilziana）含有由5-羟基愈创木基单元组成的异常木质素，这是此类聚合物在植物中自然出现的首次报道，并且一些物种的种子根本不含木质素。我们讨论了这些发现对于这些新发现的木质素类型生物合成机制的意义。
