使陸地植物遠(yuǎn)離其水生親本植物的是它們?cè)诳諝庵邢蛏习l(fā)芽,、以及依靠木質(zhì)組織支撐自身的能力。木質(zhì)結(jié)構(gòu)由纖維素組成,，其中填充木質(zhì)素分子,。大約4億7500萬年前含木質(zhì)素細(xì)胞壁的出現(xiàn)被認(rèn)為是陸地植物由水生祖先進(jìn)化過程中的一個(gè)重要變革。生物燃料研究人員對(duì)木質(zhì)素尤為感興趣,，因?yàn)樗鼘⒓?xì)胞壁聯(lián)在一起,，阻止了纖維素的提取，而后者是生物燃料產(chǎn)品的一個(gè)重要成分,。
二次生長(zhǎng)和木質(zhì)化細(xì)胞是維管植物獨(dú)有的特征,，起碼科學(xué)家是這樣認(rèn)為。美國哥倫比亞大學(xué)和斯坦福大學(xué)的一組研究人員最近鑒定出一種具有木質(zhì)細(xì)胞的海藻,。這些科學(xué)家在發(fā)表于Current Biology上的文章中指出,，“考慮到紅藻和維管植物在10億年前便已經(jīng)分化，這一發(fā)現(xiàn)使人們開始考慮這些性狀是趨同進(jìn)化還是深度保守進(jìn)化的問題”,。（生物谷Bioon.com）
生物谷推薦原始出處：
Current Biology, 22 January 2009 doi:10.1016/j.cub.2008.12.031
Discovery of Lignin in Seaweed Reveals Convergent Evolution of Cell-Wall Architecture
Patrick T. Martone1,2,7,8,,,José M. Estevez3,7,9,Fachuang Lu4,5,7,Katia Ruel6,Mark W. Denny1,2,Chris Somerville2,3,10andJohn Ralph4,5
1 Hopkins Marine Station of Stanford University, 120 Ocean View Boulevard, Pacific Grove, CA 93950, USA
2 Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA
3 Carnegie Institution, Stanford University, Stanford, CA 94305, USA
4 Department of Biochemistry, University of WisconsinMadison, Madison, WI 53706, USA
5 U.S. Dairy Forage Research Center, USDA Agricultural Research Service, Madison, WI 53706, USA
6 Centre de Recherches sur les Macromolécules Végétales (CERMAV)-CNRS, 38041 Grenoble cedex 9, France
7 These authors contributed equally to this work
8 Present address: Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
9 Present address: Laboratorio de Fisiología y Biología Molecular, IFIByNE (CONICET), FCEyN-UBA, Pab.2, Ciudad Universitaria, Buenos Aires C1428EGA, Argentina
10 Present address: Energy Biosciences Institute, University of CaliforniaBerkeley, Berkely, CA 94720, USA
Summary
Lignified cell walls are widely considered to be key innovations in the evolution of terrestrial plants from aquatic ancestors some 475 million years ago [1,2,3]. Lignins, complex aromatic heteropolymers, stiffen and fortify secondary cell walls within xylem tissues, creating a dense matrix that binds cellulose microfibrils [4] and crosslinks other wall components [5], thereby preventing the collapse of conductive vessels, lending biomechanical support to stems, and allowing plants to adopt an erect-growth habit in air. Although lignin-like compounds have been identified in primitive green algae [6,7], the presence of true lignins in nonvascular organisms, such as aquatic algae, has not been confirmed [2,3,8,9]. Here, we report the discovery of secondary walls and lignin within cells of the intertidal red alga Calliarthron cheilosporioides. Until now, such developmentally specialized cell walls have been described only in vascular plants. The finding of secondary walls and lignin in red algae raises many questions about the convergent or deeply conserved evolutionary history of these traits, given that red algae and vascular plants probably diverged more than 1 billion years ago.
