Liu Edgar, MacMillan Colleen P, Shafee Thomas, Ma Yingxuan, Ratcliffe Julian, van de Meene Allison, Bacic Antony, Humphries John, Johnson Kim L
School of BioSciences, University of Melbourne, Parkville, VIC, Australia.
CSIRO, Agriculture and Food, CSIRO Black Mountain Science and Innovation Park, Canberra, ACT, Australia.
Front Plant Sci. 2020 Dec 11;11:615392. doi: 10.3389/fpls.2020.615392. eCollection 2020.
The predominant Fascilin 1 (FAS1)-containing proteins in plants belong to the Fasciclin-Like Arabinogalactan-protein (FLA) family of extracellular glycoproteins. In addition to FAS1 domains, these multi-domain FLA proteins contain glycomotif regions predicted to direct addition of large arabinogalactan (AG) glycans and many contain signal sequences for addition of a glycosylphosphatidylinositol (GPI)-anchor to tether them to the plasma membrane. FLAs are proposed to play both structural and signaling functions by forming a range of interactions in the plant extracellular matrix, similar to FAS1-containing proteins in animals. FLA group B members contain two FAS1 domains and are not predicted to be GPI-anchored. None of the group B members have been functionally characterized or their sub-cellular location resolved, limiting understanding of their function. We investigated the group B in that is predominantly expressed in inflorescence tissues. is the most highly expressed in the stem after Group A members and that are stem specific. A FLA16-YFP fusion protein driven by the endogenous putative promoter in wild type background showed expression in cells with secondary cell walls, and FLA16 displayed characteristics of cell wall glycoproteins with moderate glycosylation. Investigation of a mutant showed loss of FLA16 leads to reduced stem length and altered biomechanical properties, likely as a result of reduced levels of cellulose. Immuno-labeling indicated support for FLA16 location to the plasma-membrane and (apoplastic) cell wall of interfascicular stem fiber cells. Together these results indicate FLA16, a two-FAS1 domain FLAs, plays a role in plant secondary cell wall synthesis and function.
植物中主要含Fascilin 1（FAS1）的蛋白质属于细胞外糖蛋白的类Fasciclin阿拉伯半乳聚糖蛋白（FLA）家族。除FAS1结构域外，这些多结构域FLA蛋白还包含预测可指导添加大型阿拉伯半乳聚糖（AG）聚糖的糖基序区域，许多还含有用于添加糖基磷脂酰肌醇（GPI）锚定以将它们 tether 到质膜的信号序列。有人提出，FLA通过在植物细胞外基质中形成一系列相互作用来发挥结构和信号传导功能，这类似于动物中含FAS1的蛋白质。FLA B组成员包含两个FAS1结构域，预计不是GPI锚定的。B组中没有成员进行过功能表征，也没有解析其亚细胞定位，这限制了对其功能的理解。我们研究了主要在花序组织中表达的B组。在A组成员和茎特异性的之后，是茎中表达最高的。在野生型背景下由内源性推定启动子驱动的FLA16 - YFP融合蛋白在具有次生细胞壁的细胞中表达，并且FLA16显示出具有适度糖基化的细胞壁糖蛋白的特征。对突变体的研究表明，FLA16的缺失导致茎长度减少和生物力学特性改变，这可能是纤维素水平降低的结果。免疫标记表明支持FLA16定位于束间茎纤维细胞的质膜和（质外体）细胞壁。这些结果共同表明，具有两个FAS1结构域的FLA16在植物次生细胞壁合成和功能中起作用。
原文中“tether them to the plasma membrane”中的“tether”可能有误，推测可能是“anchor”之类的词，这里暂按原文翻译。
