Boron bridging of rhamnogalacturonan-II in Rosa and arabidopsis cell cultures occurs mainly in the endo-membrane system and continues at a reduced rate after secretion.
Boron bridging of rhamnogalacturonan-II in Rosa and arabidopsis cell cultures occurs mainly in the endo-membrane system and continues at a reduced rate after secretion.
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DOI：
10.1093/aob/mcac119
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发表时间：
2022-11-17
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影响因子：
4.2
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中科院分区：
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鼠李糖半乳糖醛酸-II（RG-II）是初生细胞壁果胶的结构域。RG-II结构域对通过硼酸二酯桥共价交联，这是正常细胞生长所必需的。解释硼桥的确切机制和作用是困难的，因为有相互矛盾的假设是否桥主要发生在高尔基体系统内，同时分泌或细胞壁内。因此，我们探索了RG-II桥接的动力学。用[14 C]葡萄糖对罗莎和拟南芥的细胞悬浮培养物进行脉冲放射性标记，然后通过内切聚半乳糖醛酸酶消化物的聚丙烯酰胺凝胶电泳追踪新合成的[14 C]RG-II结构域的硼桥状态。14 C标记的最佳培养年龄分别为蔷薇和拟南芥的~5和~1 d。从头[14 C]多糖产生发生在前约90分钟;此后，随着放射性标记分子在壁中“老化”，对其进行跟踪。单体和（硼桥连的）二聚[14 C]RG-II结构域同时出现，两者在[14 C]葡萄糖进料的4分钟内，即在新合成的[14 C]多糖在~15-20分钟分泌到质外体中之前很久，都是可检测的。RG-II的[14 C]单体比率在4至120分钟内保持大致恒定，表明在多糖生物合成期间在高尔基体系统内发生硼桥接。然而，[14 C]二聚体在随后的15小时内略有增加，表明有限的硼桥在分泌后仍在继续。结果表明，在细胞中（因此，当在一个RG-II域的“职业生涯”）硼桥发生，有助于确定可能的生物作用的RG-II二聚化和可能的本地化的供硼糖蛋白或糖脂。
Rhamnogalacturonan-II (RG-II) is a domain of primary cell-wall pectin. Pairs of RG-II domains are covalently cross-linked via borate diester bridges, necessary for normal cell growth. Interpreting the precise mechanism and roles of boron bridging is difficult because there are conflicting hypotheses as to whether bridging occurs mainly within the Golgi system, concurrently with secretion or within the cell wall. We therefore explored the kinetics of RG-II bridging. Cell-suspension cultures of Rosa and arabidopsis were pulse-radiolabelled with [14C]glucose, then the boron bridging status of newly synthesized [14C]RG-II domains was tracked by polyacrylamide gel electrophoresis of endo-polygalacturonase digests. Optimal culture ages for 14C-labelling were ~5 and ~1 d in Rosa and arabidopsis respectively. De-novo [14C]polysaccharide production occurred for the first ~90 min; thereafter the radiolabelled molecules were tracked as they ‘aged’ in the wall. Monomeric and (boron-bridged) dimeric [14C]RG-II domains appeared simultaneously, both being detectable within 4 min of [14C]glucose feeding, i.e. well before the secretion of newly synthesized [14C]polysaccharides into the apoplast at ~15–20 min. The [14C]dimer : [14C]monomer ratio of RG-II remained approximately constant from 4 to 120 min, indicating that boron bridging was occurring within the Golgi system during polysaccharide biosynthesis. However, [14C]dimers increased slightly over the following 15 h, indicating that limited boron bridging was continuing after secretion. The results show where in the cell (and thus when in the ‘career’ of an RG-II domain) boron bridging occurs, helping to define the possible biological roles of RG-II dimerization and the probable localization of boron-donating glycoproteins or glycolipids.
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DOI：
10.1111/nph.13596
发表时间：
2016-01
期刊：
The New phytologist
影响因子：
--
作者：
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通讯作者：
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DOI：
10.1111/tpj.12403
发表时间：
2014-02
期刊：
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影响因子：
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作者：
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通讯作者：
Fry SC
影响因子：
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作者：
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通讯作者：
Azuma, J
DOI：
10.1086/336032
发表时间：
1959-01-01
期刊：
BOT GAZ
影响因子：
--
作者：
NICKELL, LOUIS G.;TULECKE, WALTER
通讯作者：
TULECKE, WALTER
影响因子：
4.3
作者：
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