Differential expression between frb1 mutant Arabidopsis and wild-type. Arabidopsis thaliana

Cell adhesion in plants is mediated predominantly by pectins, a group of complex cell wall associated polysaccharides. An Arabidopsis mutant, friable1 (frb1), was identified through a screen of T-DNA insertion lines that exhibited defective cell adhesion. Interestingly, the frb1 plants displayed both cell and organ dissociations and also ectopic organ fusions. The FRB1 gene encodes a Golgi-localized, plant specific protein with only weak sequence similarities to known proteins (DUF246). Unlike other cell adhesion deficient mutants, frb1 mutants do not have reduced levels of adhesion related cell wall polymers, such as pectins. Instead, FRB1 affects the abundance of galactose- and arabinose-containing oligosaccharides in the Golgi. Furthermore, frb1 mutants displayed alteration in pectin methylesterification, cell wall associated extensins and xyloglucan microstructure. We propose that abnormal FRB1 action has pleiotropic consequences on wall architecture, affecting both the extensin and pectin matrices, with consequent changes to the biomechanical properties of the wall and middle lamella, thereby influencing cell-cell adhesion. Microarrays were used to determine the differences in global expression of friable1 mutant plants, which have cell adhesion defects, and compared these to wild-type plants. Overall design: RNA was extracted from seedlings grown on 0.5X MS for 10 days under constant illumination.

植物细胞粘附主要由果胶（pectins）介导，果胶是一类复杂的细胞壁相关多糖（cell wall associated polysaccharides）。本研究通过对携带细胞粘附缺陷表型的T-DNA插入株系的筛选，鉴定得到拟南芥（Arabidopsis）脆性突变体friable1（frb1）。值得注意的是，frb1植株同时出现细胞与器官解离现象，以及异位器官融合。FRB1基因编码定位于高尔基体（Golgi）的植物特异性蛋白，仅与已知蛋白存在微弱序列相似性，且包含DUF246结构域。与其他细胞粘附缺陷突变体不同，frb1突变体的粘附相关细胞壁聚合物（如果胶）水平并未降低。与之相反，FRB1会影响高尔基体中含半乳糖和阿拉伯糖的寡糖丰度。此外，frb1突变体的果胶甲酯化状态、细胞壁相关伸展蛋白（extensins）以及木葡聚糖（xyloglucan）的微观结构均发生改变。我们提出，FRB1功能异常会对细胞壁结构产生多效性影响，同时作用于伸展蛋白和果胶基质，进而改变细胞壁及胞间中层（middle lamella）的生物力学特性，最终影响细胞间粘附。本研究使用微阵列（microarrays）技术，分析存在细胞粘附缺陷的friable1突变体植株的全局基因表达差异，并将其与野生型植株进行对比。实验整体设计：从在0.5倍MS培养基上连续光照培养10天的幼苗中提取总RNA。