Hotte Naomi S C, Deyholos Michael K
Department of Biological Sciences, Edmonton, T6G 2E9, Canada.
BMC Plant Biol. 2008 Apr 30;8:52. doi: 10.1186/1471-2229-8-52.
Bast fibres from the phloem tissues of flax are scientifically interesting and economically useful due in part to a dynamic system of secondary cell wall deposition. To better understand the molecular mechanisms underlying the process of cell wall development in flax, we extracted proteins from individually dissected phloem fibres (i.e. individual cells) at an early stage of secondary cell wall development, and compared these extracts to protein extracts from surrounding, non-fibre cells of the cortex, using fluorescent (DiGE) labels and 2D-gel electrophoresis, with identities assigned to some proteins by mass spectrometry.
The abundance of many proteins in fibres was notably different from the surrounding non-fibre cells of the cortex, with approximately 13% of the 1,850 detectable spots being significantly (> 1.5 fold, p < or = 0.05) enriched in fibres. Following mass spectrometry, we assigned identity to 114 spots, of which 51 were significantly enriched in fibres. We observed that a K+ channel subunit, annexins, porins, secretory pathway components, beta-amylase, beta-galactosidase and pectin and galactan biosynthetic enzymes were among the most highly enriched proteins detected in developing flax fibres, with many of these proteins showing electrophoretic patterns consistent with post-translational modifications.
The fibre-enriched proteins we identified are consistent with the dynamic process of secondary wall deposition previously suggested by histological and biochemical analyses, and particularly the importance of galactans and the secretory pathway in this process. The apparent abundance of beta-amylase suggests that starch may be an unappreciated source of materials for cell wall biogenesis in flax bast fibres. Furthermore, our observations confirm previous reports that correlate accumulation proteins such as annexins, and specific heat shock proteins with secondary cell wall deposition.
亚麻韧皮组织中的韧皮纤维在科学上具有重要意义且在经济上具有实用价值，部分原因在于其动态的次生细胞壁沉积系统。为了更好地理解亚麻细胞壁发育过程的分子机制，我们在次生细胞壁发育的早期阶段从单独解剖的韧皮纤维（即单个细胞）中提取蛋白质，并使用荧光（差异凝胶电泳，DiGE）标记和二维凝胶电泳，将这些提取物与来自皮层周围非纤维细胞的蛋白质提取物进行比较，通过质谱分析确定了一些蛋白质的身份。
纤维中许多蛋白质的丰度与皮层周围的非纤维细胞显著不同，在1850个可检测斑点中，约13%在纤维中显著富集（>1.5倍，p≤0.05）。经过质谱分析，我们确定了114个斑点的身份，其中51个在纤维中显著富集。我们观察到，钾离子通道亚基、膜联蛋白、孔蛋白、分泌途径成分、β-淀粉酶、β-半乳糖苷酶以及果胶和半乳聚糖生物合成酶是在发育中的亚麻纤维中检测到的最高度富集的蛋白质，其中许多蛋白质的电泳图谱显示出与翻译后修饰一致的特征。
我们鉴定出的富含纤维的蛋白质与先前组织学和生化分析所表明的次生壁沉积动态过程一致，特别是半乳聚糖和分泌途径在这一过程中的重要性。β-淀粉酶的明显丰度表明淀粉可能是亚麻韧皮纤维细胞壁生物合成中未被重视的物质来源。此外，我们的观察结果证实了先前的报道，即膜联蛋白等积累蛋白以及特定的热休克蛋白与次生细胞壁沉积相关。
