Harrington Gregory N, Dibley Katherine E, Ritchie Raymond J, Offler Christina E, Patrick John W
School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia.
Biology A-08, University of Sydney, Sydney, NSW 2006, Australia.
Funct Plant Biol. 2005 Nov;32(11):987-995. doi: 10.1071/FP05081.
Cotyledons of broad bean (Vicia faba L.) develop in an apoplasmic environment that shifts in composition from one dominated by hexoses to one dominated by sucrose. During the latter phase of development, sucrose / H symporter activity and expression is restricted to cotyledon epidermal transfer cell complexes that support sucrose fluxes that are 8.5-fold higher than those exhibited by the storage parenchyma. In contrast, the flux difference between these cotyledon tissues is only 1.7-fold for hexoses. Glucose and fructose uptake was shown to be sensitive to PCMBS and phloridzin, both of which slow H-sugar transport. A low K (or high affinity transporter, HAT) mechanism transports glucose and glucose-analogues exclusively. No HAT system for fructose could be found. A high K (low affinity transporter, LAT) mechanism transports a broader range of hexoses, including glucose and fructose. Consistent with glucose and fructose transport being H-coupled, their uptake was inhibited by dissipating the proton motive force (pmf) by treating cotyledons with carbonyl cyanide m-chlorophenol hydrazone, propionic acid or tetraphenylphosphonium ion. Erythrosin B inhibited hexose uptake, indicating a role for the P-type H-ATPase in establishing the pmf. It is concluded that H-coupled glucose and fructose transport mechanisms occur at plasma membranes of dermal transfer cell complexes and storage parenchyma cells. These transport mechanisms are active during pre- and storage phases of cotyledon development. However, hexose symport only makes a quantitative contribution to cotyledon biomass gain during the pre-storage stage of development.
蚕豆（Vicia faba L.）的子叶在质外体环境中发育，该环境的成分从以己糖为主转变为以蔗糖为主。在发育的后期阶段，蔗糖/H共转运体的活性和表达仅限于子叶表皮转移细胞复合体，该复合体支持的蔗糖通量比贮藏薄壁组织高8.5倍。相比之下，这些子叶组织之间己糖的通量差异仅为1.7倍。葡萄糖和果糖的摄取对PCMBS和根皮苷敏感，这两种物质都会减缓H-糖的运输。低亲和力（或高亲和力转运体，HAT）机制专门运输葡萄糖和葡萄糖类似物。未发现果糖的HAT系统。高亲和力（低亲和力转运体，LAT）机制运输范围更广的己糖，包括葡萄糖和果糖。与葡萄糖和果糖的运输与H偶联一致，通过用羰基氰化物间氯苯腙、丙酸或四苯基鏻离子处理子叶来消散质子动力势（pmf），从而抑制了它们的摄取。赤藓红B抑制己糖摄取，表明P型H-ATPase在建立pmf中起作用。得出的结论是，H偶联的葡萄糖和果糖运输机制发生在表皮转移细胞复合体和贮藏薄壁组织细胞的质膜上。这些运输机制在子叶发育的预贮藏期和贮藏期都很活跃。然而，己糖共转运仅在发育的预贮藏阶段对子叶生物量的增加有定量贡献。
