The Arabidopsis vacuolar sugar transporter SWEET2 limits carbon sequestration from roots and restricts Pythium infection
The Arabidopsis vacuolar sugar transporter SWEET2 limits carbon sequestration from roots and restricts Pythium infection
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DOI：
10.1111/tpj.12948
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发表时间：
2015-09-01
期刊：
影响因子：
7.2
通讯作者：
Guo, Woei-Jiun
中科院分区：
文献类型：
--
作者：
Chen, Hsin-Yi;Huh, Jung-Hyun;Guo, Woei-Jiun
植物根将其同化碳的很大一部分分泌到根际。假定的糖转运蛋白 SWEET2 在拟南芥根中高度表达。 SWEET2-葡萄糖醛酸酶融合物的表达模式证实，SWEET2 在根细胞中高度积累，因此可能有助于糖分泌，特别是根尖表皮细胞的糖分泌。 SWEET2-绿色荧光蛋白融合物定位于液泡膜，吞噬了主要的糖储存室。对酵母中 SWEET2 活性的功能分析表明，葡萄糖类似物 2-脱氧葡萄糖的摄取活性较低，这与葡萄糖穿过液泡膜转运的作用一致。功能丧失的 sweet2 突变体表现出对过量葡萄糖的耐受性降低、叶片中葡萄糖积累降低、根部葡萄糖衍生碳流出增加 15-25%，这表明 SWEET2 具有防止根组织糖损失的作用。在腐霉感染期间，SWEET2 根表达被诱导超过 10 倍。重要的是，sweet2 突变体更容易受到卵菌的影响，感染后表现出生长受损。我们认为根表达的液泡 SWEET2 可能通过减少液泡中隔离的葡萄糖的可用性来调节糖分泌，从而限制根际的碳损失。此外，由于 SWEET2 活性，根际糖的利用率降低有助于对腐霉的抗性。
Plant roots secrete a significant portion of their assimilated carbon into the rhizosphere. The putative sugar transporter SWEET2 is highly expressed in Arabidopsis roots. Expression patterns of SWEET2--glucuronidase fusions confirmed that SWEET2 accumulates highly in root cells and thus may contribute to sugar secretion, specifically from epidermal cells of the root apex. SWEET2-green fluorescent protein fusions localized to the tonoplast, which engulfs the major sugar storage compartment. Functional analysis of SWEET2 activity in yeast showed low uptake activity for the glucose analog 2-deoxyglucose, consistent with a role in the transport of glucose across the tonoplast. Loss-of-function sweet2 mutants showed reduced tolerance to excess glucose, lower glucose accumulation in leaves, and 15-25% higher glucose-derived carbon efflux from roots, suggesting that SWEET2 has a role in preventing the loss of sugar from root tissue. SWEET2 root expression was induced more than 10-fold during Pythium infection. Importantly, sweet2 mutants were more susceptible to the oomycete, showing impaired growth after infection. We propose that root-expressed vacuolar SWEET2 modulates sugar secretion, possibly by reducing the availability of glucose sequestered in the vacuole, thereby limiting carbon loss to the rhizosphere. Moreover, the reduced availability of sugar in the rhizosphere due to SWEET2 activity contributes to resistance to Pythium.