Noronha Henrique, Conde Carlos, Delrot Serge, Gerós Hernâni
Centro de Investigação e de Tecnologias Agro-ambientais e Biológicas CITAB, Vila Real, Portugal.
Planta. 2015 Oct;242(4):909-20. doi: 10.1007/s00425-015-2329-x. Epub 2015 May 26.
Two grapevine glucose-6-Pi plastidial transporters differently expressed in plant organs and in response to environmental and hormonal signals are characterized. They are involved in starch accumulation in berries and canes. In grapevine, starch accumulation in the trunk is important for winter storage of carbon and in the flower for reproductive development. Berries also accumulate starch in their plastids, which are also involved in the synthesis of aroma compounds important for fruit quality. The present work characterizes two glucose-phosphate translocators (VvGPT1, VvGPT2) that control the accumulation of starch in grape amyloplasts. Three different splicing variants identified for VvGPT2 (VvGPT2α, VvGPT2β and VvGPT2Ω) were more expressed in the leaves than in other organs. In contrast, VvGPT1 transcripts were more abundant in mature berries, canes and flowers than in the leaves. Expression of 35S-VvGPT1-GFP and 35S-VvGPT2Ω-GFP in tobacco leaf epidermal cells showed that the fusion proteins localized at the plastidial envelope. Complementation of the Arabidopsis pgi1-1 mutant impaired in leaf starch synthesis restored its ability to synthesize starch, demonstrating that VvGPT1 and VvGPT2Ω mediate the transport of glucose-6-Pi across the plastidial envelope. In grape cell suspensions, ABA, light and galactinol, together with sucrose and fructose, significantly increased the transcript abundance of VvGPT1, whereas VvGPT2Ω expression was affected only by sucrose. In addition, elicitation with methyl jasmonate strongly upregulated VvGPT1, VvGPT2Ω and VvPAL1, suggesting a role for GPTs in the production of secondary compounds in grapevine. Moreover, in grapevines cultivated in field conditions, VvGPT1 expression was higher in berries more exposed to the sun and subjected to higher temperatures. Although both VvGPT1 and VvGPT2 mediate the same function at the molecular level, they exhibit different expression levels and regulation in plant organs and in response to environmental and hormonal signals.
对两种在植物器官中表达不同且对环境和激素信号有响应的葡萄葡萄糖-6-磷酸质体转运体进行了表征。它们参与浆果和茎中淀粉的积累。在葡萄中，树干中淀粉的积累对碳的冬季储存很重要，而在花中对生殖发育很重要。浆果在其质体中也积累淀粉，质体还参与对果实品质很重要的香气化合物的合成。目前的工作表征了两种控制葡萄淀粉体中淀粉积累的葡萄糖-磷酸转运体（VvGPT1、VvGPT2）。为VvGPT2鉴定出的三种不同剪接变体（VvGPT2α、VvGPT2β和VvGPT2Ω）在叶片中的表达高于其他器官。相比之下，VvGPT1转录本在成熟浆果、茎和花中比在叶片中更丰富。在烟草叶表皮细胞中35S-VvGPT1-GFP和35S-VvGPT2Ω-GFP的表达表明融合蛋白定位于质体包膜。在叶片淀粉合成受损的拟南芥pgi1-1突变体的互补恢复了其合成淀粉的能力，证明VvGPT1和VvGPT2Ω介导葡萄糖-6-磷酸穿过质体包膜的转运。在葡萄细胞悬浮液中，脱落酸、光和半乳糖醇与蔗糖和果糖一起显著增加了VvGPT1的转录本丰度，而VvGPT2Ω的表达仅受蔗糖影响。此外，用茉莉酸甲酯诱导强烈上调了VvGPT1、VvGPT2Ω和VvPAL1，表明GPTs在葡萄次生化合物的产生中起作用。此外，在田间条件下种植的葡萄中，VvGPT1在更多暴露于阳光和更高温度的浆果中表达更高。虽然VvGPT1和VvGPT2在分子水平上介导相同的功能，但它们在植物器官中以及对环境和激素信号的响应中表现出不同的表达水平和调控。
