UDP-arabinopyranose mutase gene expressions are required for the biosynthesis of the arabinose side chain of both pectin and arabinoxyloglucan, and normal leaf expansion in Nicotiana tabacum
UDP-arabinopyranose mutase gene expressions are required for the biosynthesis of the arabinose side chain of both pectin and arabinoxyloglucan, and normal leaf expansion in Nicotiana tabacum
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DOI：
10.1007/s10265-017-0985-6
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发表时间：
2018-03-01
影响因子：
2.8
通讯作者：
Iwai, Hiroaki
中科院分区：
文献类型：
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作者：
Honta, Hideyuki;Inamura, Takuya;Iwai, Hiroaki
植物细胞壁由多糖如纤维素、半纤维素和果胶组成，其位置和功能根据植物类型而不同。阿拉伯糖是许多不同细胞壁组分的组成部分，包括果胶鼠李糖半乳糖醛酸聚糖I（RG-I）和II（RG-II）、葡糖醛酸阿拉伯聚糖（GAX）和阿拉伯木葡聚糖（AXG）。阿拉伯糖主要存在于呋喃糖中，而不是热力学更稳定的吡喃糖形式。UDP-吡喃阿拉伯糖变位酶（UAMs）在水稻中能将UDP-吡喃阿拉伯糖（UDP-Arap）转化为UDP-阿拉伯呋喃糖（UDP-Araf）。UAM参与多糖的生物合成和发育过程。阿拉伯糖残基可以是许多多糖的组分，包括支链（1 -> 5）-α-阿拉伯聚糖、果胶多糖中的阿拉伯半乳聚糖和阿拉伯木葡聚糖，其在茄科植物的细胞壁中丰富。因此，为了阐明UAM和阿拉伯聚糖侧链的作用，我们分析了烟草（Nicotiana tabacum L.）中的UAM RNA干扰转化体。烟草UAM基因家族由四个成员组成。我们产生了RNAi转化体（NtUAM-KD）以下调所有四个UAM成员。NtUAM-KD表现出愈伤组织样结构形式的异常叶发育和叶表皮中的许多孔。在NtUAM-KD叶的组织中观察到果胶阿拉伯聚糖含量的明显降低。在NtUAM-KD中，富含木葡聚糖的细胞壁级分中的阿拉伯糖/木糖比率急剧降低。这些结果表明，在茄科植物的RG-I和AXG的Ara侧链生物合成所需的UAMs，阿拉伯糖介导的细胞壁网络可能是重要的正常叶片扩展。
Plant cell walls are composed of polysaccharides such as cellulose, hemicelluloses, and pectins, whose location and function differ depending on plant type. Arabinose is a constituent of many different cell wall components, including pectic rhamnogalacturonan I (RG-I) and II (RG-II), glucuronoarabinoxylans (GAX), and arabinoxyloglucan (AXG). Arabinose is found predominantly in the furanose rather than in the thermodynamically more stable pyranose form. The UDP-arabinopyranose mutases (UAMs) have been demonstrated to convert UDP-arabinopyranose (UDP-Arap) to UDP-arabinofuranose (UDP-Araf) in rice (Oryza sativa L.). The UAMs have been implicated in polysaccharide biosynthesis and developmental processes. Arabinose residues could be a component of many polysaccharides, including branched (1 -> 5)-alpha-arabinans, arabinogalactans in pectic polysaccharides, and arabinoxyloglucans, which are abundant in the cell walls of solanaceous plants. Therefore, to elucidate the role of UAMs and arabinan side chains, we analyzed the UAM RNA interference transformants in tobacco (Nicotiana tabacum L.). The tobacco UAM gene family consists of four members. We generated RNAi transformants (NtUAM-KD) to down-regulate all four of the UAM members. The NtUAM-KD showed abnormal leaf development in the form of a callus-like structure and many holes in the leaf epidermis. A clear reduction in the pectic arabinan content was observed in the tissue of the NtUAM-KD leaf. The arabinose/xylose ratio in the xyloglucan-rich cell wall fraction was drastically reduced in NtUAM-KD. These results suggest that UAMs are required for Ara side chain biosynthesis in both RG-I and AXG in Solanaceae plants, and that arabinan-mediated cell wall networks might be important for normal leaf expansion.