Butowt Rafal, Granot David, Rodríguez-García María Isabel
Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, E-18008 Granada, Spain.
Plant Cell Physiol. 2003 Nov;44(11):1152-61. doi: 10.1093/pcp/pcg149.
Metabolite-specific transporters are present in the inner membrane of the plastid envelope allowing transport between the plastid and other cellular compartments. A plastidic glucose translocator (pGlcT) in leaf mesophyll cells transports glucose from chloroplast stroma to the cytosol after amylolytic starch degradation at night. Here we report the cloning of a pGlcT expressed in olive fruits (Olea europea L.). Our results showed high expression of pGlcT in non-green heterotrophic fruit tissues. Expression of pGlcT in olive fruits was somewhat higher compared to leaves, and continued until the black, mature fruit stage. We cloned part of tomato pGlcT and found that it is also expressed throughout fruit development implying a role for pGlcT in heterotrophic tissues. Light and electron microscopic characterization of plastid structural changes during olive fruit ripening revealed the transition of chloroplast-like plastids into starchless, non-green plastids; in mature olive fruits only chromoplasts were present. Together, these findings suggest that olive pGlcT is abundant in chromoplasts during structural changes, and provide evidence that pGlcT may play different physiological roles in ripening fruits and possibly in other non-photosynthetic organs.
代谢物特异性转运体存在于质体包膜的内膜中，可实现质体与其他细胞区室之间的转运。夜间淀粉分解后，叶肉细胞中的质体葡萄糖转运体（pGlcT）将葡萄糖从叶绿体基质转运至细胞质。本文报道了在油橄榄果实（油橄榄）中表达的一种pGlcT的克隆。我们的结果显示pGlcT在非绿色异养果实组织中高表达。与叶片相比，pGlcT在油橄榄果实中的表达略高，并持续至黑色成熟果实阶段。我们克隆了番茄pGlcT的部分序列，发现其在果实发育过程中也持续表达，这表明pGlcT在异养组织中发挥作用。油橄榄果实成熟过程中质体结构变化的光镜和电镜特征显示，类叶绿体向无淀粉、非绿色质体转变；在成熟油橄榄果实中仅存在有色体。这些发现共同表明，在结构变化过程中，油橄榄pGlcT在有色体中含量丰富，并提供了证据证明pGlcT可能在成熟果实以及可能在其他非光合器官中发挥不同的生理作用。
