Suen Der Fen, Wu Sherry S H, Chang Han Chang, Dhugga Kanwarpal S, Huang Anthony H C
Center for Plant Cell Biology, Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA.
J Biol Chem. 2003 Oct 31;278(44):43672-81. doi: 10.1074/jbc.M307843200. Epub 2003 Aug 20.
The surface of a pollen grain consists of an outermost coat and an underlying wall. In maize (Zea mays L.), the pollen coat contains two major proteins derived from the adjacent tapetum cells in the anthers. One of the proteins is a 35-kDa endoxylanase (Wu, S. S. H., Suen, D. F., Chang, H. C., and Huang, A. H. C. (2002) J. Biol. Chem. 277, 49055-49064). The other protein of 70 kDa was purified to homogeneity and shown to be a beta-glucanase. Its gene sequence and the developmental pattern of its mRNA differ from those of the known beta-glucanases that hydrolyze the callose wall of the microspore tetrad. Mature pollen placed in a liquid medium released about nine major proteins. These proteins were partially sequenced and identified via GenBank trade mark data bases, and some had not been previously reported to be in pollen. They appear to have wall-loosening, structural, and enzymatic functions. A novel pollen wall-bound protein of 17 kDa has a unique pattern of cysteine distribution in its sequence (six tandem repeats of CX3CX10-15) that could chelate cations and form signal-receiving finger motifs. These pollen-released proteins were synthesized in the pollen interior, and their mRNA increased during pollen maturation and germination. They were localized mainly in the pollen tube wall. The pollen shell was isolated and found to contain no detectable proteins. We suggest that the pollen-coat beta-glucanase and xylanase hydrolyze the stigma wall for pollen tube entry and that the pollen secrete proteins to loosen or become new wall constituents of the tube and to break the wall of the transmitting track for tube advance.
花粉粒的表面由最外层的包膜和其下的壁组成。在玉米（Zea mays L.）中，花粉包膜包含两种主要蛋白质，它们源自花药中相邻的绒毡层细胞。其中一种蛋白质是35 kDa的内切木聚糖酶（Wu, S. S. H., Suen, D. F., Chang, H. C., and Huang, A. H. C. (2002) J. Biol. Chem. 277, 49055 - 49064）。另一种70 kDa的蛋白质被纯化至同质，并被证明是一种β - 葡聚糖酶。其基因序列及其mRNA的发育模式与已知水解小孢子四分体胼胝质壁的β - 葡聚糖酶不同。置于液体培养基中的成熟花粉释放出约九种主要蛋白质。这些蛋白质经过部分测序，并通过GenBank商标数据库进行鉴定，其中一些以前未曾报道存在于花粉中。它们似乎具有细胞壁松弛、结构和酶促功能。一种新的17 kDa花粉壁结合蛋白在其序列中具有独特的半胱氨酸分布模式（CX3CX10 - 15的六个串联重复），可以螯合阳离子并形成信号接收指基序。这些花粉释放的蛋白质在花粉内部合成，其mRNA在花粉成熟和萌发过程中增加。它们主要定位在花粉管壁中。分离出的花粉壳未检测到蛋白质。我们认为，花粉包膜β - 葡聚糖酶和木聚糖酶水解柱头壁以便花粉管进入，并且花粉分泌蛋白质以松弛或成为花粉管的新壁成分，并打破传递通道的壁以便花粉管前进。
