ARC Centre of Excellence in Plant Cell Walls, School of Botany, University of Melbourne, Melbourne, Australia.
PLoS One. 2011;6(9):e25154. doi: 10.1371/journal.pone.0025154. Epub 2011 Sep 22.
The fasciclin-like arabinogalactan-proteins (FLAs) are an enigmatic class of 21 members within the larger family of arabinogalactan-proteins (AGPs) in Arabidopsis thaliana. Located at the cell surface, in the cell wall/plasma membrane, they are implicated in many developmental roles yet their function remains largely undefined. Fasciclin (FAS) domains are putative cell-adhesion domains found in extracellular matrix proteins of organisms from all kingdoms, but the juxtaposition of FAS domains with highly glycosylated AGP domains is unique to plants. Recent studies have started to elucidate the role of FLAs in Arabidopsis development. FLAs containing a single FAS domain are important for the integrity and elasticity of the plant cell wall matrix (FLA11 and FLA12) and FLA3 is involved in microspore development. FLA4/SOS5 with two FAS domains and two AGP domains has a role in maintaining proper cell expansion under salt stressed conditions. The role of other FLAs remains to be uncovered.
METHOD/PRINCIPAL FINDINGS: Here we describe the characterisation of a T-DNA insertion mutant in the FLA1 gene (At5g55730). Under standard growth conditions fla1-1 mutants have no obvious phenotype. Based on gene expression studies, a putative role for FLA1 in callus induction was investigated and revealed that fla1-1 has a reduced ability to regenerate shoots in an in vitro shoot-induction assay. Analysis of FLA1p:GUS reporter lines show that FLA1 is expressed in several tissues including stomata, trichomes, the vasculature of leaves, the primary root tip and in lateral roots near the junction of the primary root.
The results of the developmental expression of FLA1 and characterisation of the fla1 mutant support a role for FLA1 in the early events of lateral root development and shoot development in tissue culture, prior to cell-type specification.
在拟南芥的阿拉伯半乳聚糖蛋白（AGP）大家族中，纤维粘连蛋白样阿拉伯半乳聚糖蛋白（FLAs）是一个谜一般的 21 个成员的类别。它们位于细胞表面、细胞壁/质膜上，被牵连到许多发育角色中，但它们的功能仍然很大程度上未被定义。FAS 结构域是假定的细胞粘附结构域，存在于所有生物界的细胞外基质蛋白中，但 FAS 结构域与高度糖基化的 AGP 结构域的并置是植物特有的。最近的研究已经开始阐明 FLAs 在拟南芥发育中的作用。含有单个 FAS 结构域的 FLAs 对植物细胞壁基质的完整性和弹性很重要（FLA11 和 FLA12），而 FLA3 则参与小孢子的发育。含有两个 FAS 结构域和两个 AGP 结构域的 FLA4/SOS5 在盐胁迫条件下维持适当的细胞扩张中起作用。其他 FLAs 的作用仍有待发现。
方法/主要发现：在这里，我们描述了 FLA1 基因（At5g55730）的 T-DNA 插入突变体的特征。在标准生长条件下，fla1-1 突变体没有明显的表型。基于基因表达研究，研究了 FLA1 在愈伤组织诱导中的作用，并发现 fla1-1 在体外芽诱导测定中再生芽的能力降低。FLA1p:GUS 报告系的分析表明，FLA1 在包括气孔、毛状体、叶片脉管系统、主根尖和主根和侧根交界处附近的侧根在内的几种组织中表达。
FLA1 的发育表达分析和 fla1 突变体的特征支持 FLA1 在侧根发育和组织培养中芽发育的早期事件中的作用，在细胞类型特化之前。
