Roppolo Daniele, Boeckmann Brigitte, Pfister Alexandre, Boutet Emmanuel, Rubio Maria C, Dénervaud-Tendon Valérie, Vermeer Joop E M, Gheyselinck Jacqueline, Xenarios Ioannis, Geldner Niko
Department of Plant Molecular Biology, University of Lausanne, Quartier Sorge, Lausanne 1015, Switzerland (D.R., A.P., M.C.R., V.D.-T., J.E.M.V., N.G.);Swiss Institute of Bioinformatics, Centre Médical Universitaire, 1211 Geneva 4, Switzerland (B.B., E.B., I.X.);Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, 50080 Zaragoza, Spain (M.C.R.);Vital-IT Group and University of Lausanne, Quartier Sorge, Bâtiment Génopode, Lausanne 1015, Switzerland (I.X.); andInstitute of Plant Sciences, University of Bern, 3013 Bern, Switzerland (D.R., J.G.)
Department of Plant Molecular Biology, University of Lausanne, Quartier Sorge, Lausanne 1015, Switzerland (D.R., A.P., M.C.R., V.D.-T., J.E.M.V., N.G.);Swiss Institute of Bioinformatics, Centre Médical Universitaire, 1211 Geneva 4, Switzerland (B.B., E.B., I.X.);Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, 50080 Zaragoza, Spain (M.C.R.);Vital-IT Group and University of Lausanne, Quartier Sorge, Bâtiment Génopode, Lausanne 1015, Switzerland (I.X.); andInstitute of Plant Sciences, University of Bern, 3013 Bern, Switzerland (D.R., J.G.).
Plant Physiol. 2014 Aug;165(4):1709-1722. doi: 10.1104/pp.114.239137. Epub 2014 Jun 11.
CASPARIAN STRIP MEMBRANE DOMAIN PROTEINS (CASPs) are four-membrane-span proteins that mediate the deposition of Casparian strips in the endodermis by recruiting the lignin polymerization machinery. CASPs show high stability in their membrane domain, which presents all the hallmarks of a membrane scaffold. Here, we characterized the large family of CASP-like (CASPL) proteins. CASPLs were found in all major divisions of land plants as well as in green algae; homologs outside of the plant kingdom were identified as members of the MARVEL protein family. When ectopically expressed in the endodermis, most CASPLs were able to integrate the CASP membrane domain, which suggests that CASPLs share with CASPs the propensity to form transmembrane scaffolds. Extracellular loops are not necessary for generating the scaffold, since CASP1 was still able to localize correctly when either one of the extracellular loops was deleted. The CASP first extracellular loop was found conserved in euphyllophytes but absent in plants lacking Casparian strips, an observation that may contribute to the study of Casparian strip and root evolution. In Arabidopsis (Arabidopsis thaliana), CASPL showed specific expression in a variety of cell types, such as trichomes, abscission zone cells, peripheral root cap cells, and xylem pole pericycle cells.
凯氏带膜结构域蛋白（CASPs）是具有四个跨膜结构域的蛋白，通过募集木质素聚合机制介导内皮层中凯氏带的沉积。CASPs在其膜结构域中表现出高度稳定性，呈现出膜支架的所有特征。在此，我们对一大类类CASP（CASPL）蛋白进行了表征。在陆地植物的所有主要分类群以及绿藻中都发现了CASPLs；植物界以外的同源物被鉴定为MARVEL蛋白家族的成员。当在内皮层中异位表达时，大多数CASPLs能够整合CASP膜结构域，这表明CASPLs与CASPs一样具有形成跨膜支架的倾向。由于当任何一个细胞外环缺失时，CASP1仍能正确定位，因此细胞外环对于生成支架不是必需的。发现CASP的第一个细胞外环在真叶植物中保守，但在缺乏凯氏带的植物中不存在，这一观察结果可能有助于凯氏带和根进化的研究。在拟南芥中，CASPL在多种细胞类型中特异性表达，如毛状体、脱落区细胞、外周根冠细胞和木质部极周皮层细胞。
