López-Serrano M, Fernández María D, Pomar Federico, Pedreño María A, Ros Barceló A
Department of Plant Biology (Plant Physiology), University of Murcia, E-30100 Murcia, Spain.
J Exp Bot. 2004 Feb;55(396):423-31. doi: 10.1093/jxb/erh036.
The nature of the peroxidase isoenzyme complement responsible for cell wall lignification in both Zinnia elegans seedlings and Z. elegans tracheary single-cell cultures have been studied. Results showed that both hypocotyls and stems from lignifying Z. elegans seedlings express a cell wall-located basic peroxidase of pI approximately 10.2, which was purified to homogeneity. Molecular mass determination under non-denaturing conditions showed an M(r) of about 43 000, similar to that of other plant peroxidases. The purified Z. elegans peroxidase showed absorption maxima at 403 (Soret band), and at 496-501 and 632-635 (alpha and beta absorption bands), indicating that this enzyme is a high spin ferric haem protein, belonging to the plant peroxidase superfamily, the prosthetic group being ferric protoporphyrin IX. The N-terminal amino acid sequence of this Z. elegans basic peroxidase was KVAVSPLS (peptide motif in bold), which shows strong homologies with the N-amino acid terminus of other strongly basic plant peroxidases. Isoenzyme and western blot analyses showed that this peroxidase isoenzyme is also expressed in trans-differentiating Z. elegans tracheary single-cell cultures. The results also showed that Z. elegans tracheary single-cell cultures not only express the same peroxidase isoenzyme as the Z. elegans lignifying xylem, but that this peroxidase isoenzyme acts as a marker of tracheary element differentiation in Z. elegans mesophyll single-cell cultures. From these results, it may be concluded that Z. elegans uses a single programme, i.e. an identical peroxidase isoenzyme complement, for lignification of the xylem, regardless of the existence of different ontogenesis pathways from either mesophyll cells (in the case of tracheary elements) or cambial derivatives (in the case of xylem vessels).
对百日草幼苗和百日草管状单细胞培养物中负责细胞壁木质化的过氧化物酶同工酶组成的性质进行了研究。结果表明，来自木质化百日草幼苗的下胚轴和茎均表达一种位于细胞壁的碱性过氧化物酶，其pI约为10.2，已纯化至同质。在非变性条件下测定的分子量显示M(r)约为43000，与其他植物过氧化物酶相似。纯化的百日草过氧化物酶在403nm（Soret带）以及496 - 501nm和632 - 635nm（α和β吸收带）处有吸收最大值，表明该酶是一种高自旋铁血红素蛋白，属于植物过氧化物酶超家族，辅基为铁原卟啉IX。这种百日草碱性过氧化物酶的N端氨基酸序列为KVAVSPLS（加粗的肽基序），与其他强碱性植物过氧化物酶的N端氨基酸序列有很强的同源性。同工酶分析和蛋白质印迹分析表明，这种过氧化物酶同工酶也在百日草管状单细胞培养物的转分化过程中表达。结果还表明，百日草管状单细胞培养物不仅表达与百日草木质化木质部相同的过氧化物酶同工酶，而且这种过氧化物酶同工酶是百日草叶肉单细胞培养物中管状分子分化的标志物。从这些结果可以得出结论，无论从叶肉细胞（对于管状分子而言）还是形成层衍生物（对于木质部导管而言）存在不同的个体发育途径，百日草都使用单一程序，即相同的过氧化物酶同工酶组成来进行木质部的木质化。
