Role of UDP-Glucuronic Acid Decarboxylase in Xylan Biosynthesis in Arabidopsis

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• 作者：Beiqing Kuang¹ ; ² ; ⁹ ; Xianhai Zhao¹ ; ² ; ⁹ ; Chun Zhou¹ ; ² ; Wei Zeng³ ; Junli Ren⁴ ; Berit Ebert³ ; Cherie T. Beahan³ ; Xiaomei Deng² ; Qingyin Zeng⁵ ; Gongke Zhou⁶ ; Monika S. Doblin³ ; Joshua L. Heazlewood³ ; ⁷ ; Antony Bacic³ ; Xiaoyang Chen¹ ; ² ; ⁸ ; ^{xychen@scau.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Ai-Min Wu¹ ; ² ; ⁸ ; ^{wuaimin@scau.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：UDP-Xylose ; xylan ; UDP-Glucuronic acid decarboxylase ; localization
• 刊名：Molecular Plant
• 出版年：2016
• 出版时间：1 August 2016
• 年：2016
• 卷：9
• 期：8
• 页码：1119-1131
• 全文大小：1571 K

文摘

UDP-xylose (UDP-Xyl) is the Xyl donor used in the synthesis of major plant cell-wall polysaccharides such as xylan (as a backbone-chain monosaccharide) and xyloglucan (as a branching monosaccharide). The biosynthesis of UDP-Xyl from UDP-glucuronic acid (UDP-GlcA) is irreversibly catalyzed by UDP-glucuronic acid decarboxylase (UXS). Until now, little has been known about the physiological roles of UXS in plants. Here, we report that AtUXS1, AtUXS2, and AtUXS4 are located in the Golgi apparatus whereas AtUXS3, AtUXS5, and AtUXS6 are located in the cytosol. Although all six single AtUXS T-DNA mutants and the uxs1 usx2 uxs4 triple mutant show no obvious phenotype, the uxs3 uxs5 uxs6 triple mutant has an irregular xylem phenotype. Monosaccharide analysis showed that Xyl levels decreased in uxs3 uxs5 uxs6 and linkage analysis confirmed that the xylan content in uxs3 xus5 uxs6 declined, indicating that UDP-Xyl from cytosol AtUXS participates in xylan synthesis. Gel-permeation chromatography showed that the molecular weight of non-cellulosic polysaccharides in the triple mutants, mainly composed of xylans, is lower than that in the wild type, suggesting an effect on the elongation of the xylan backbone. Upon saccharification treatment stems of the uxs3uxs5uxs6 triple mutants released monosaccharides with a higher efficiency than those of the wild type. Taken together, our results indicate that the cytosol UXS plays a more important role than the Golgi-localized UXS in xylan biosynthesis.