Distribution Of Energy Storage Substances In Arabidopsis Source And Sink Organs By Glucose-6-phosphate Translocater

During photosynthesis,plants convert the light energy and water to oxgen and sucrose in the source tissue.The distribution of carbohydrates synthesized from the source organs to various sink organs is a highly regulated process,which is essential to maintain the autotrophic growth and reproduction of plants.Starch and lipid serves as the main storage compounds to provide carbon/energy sourcese in sink tissues in plants.This research is foucused on the underlying molecular mechanism of distribution of storage compounds between sources organs and sink organs in Arabidopsis.Here,we found that glucose-6-phosphate translocater 1?GPT1?,a plastid-localized Glc-6-P importer,plays a vital role in this process.GPT1 protein is localized on the membrane of non-photosynthetic plastids and transports glucose-6-phosphate?Glc-6-P?into plastids for starch and/or fatty acid biosynthesis.GPT1 is an esstial gene in Arabidopsis for gpt1 mutant is lethal.To overcome this,in this study,we constructed estradiol inducible GPT1 RNAi;P_GPT1:GPT1-eYFP;gpt1^-/-,to explore the function of GPT1 on starch accumulation in the source and sink organs.GPT1 RNAi resulted in delayed growth of Arabidopsis seedlings with excessive accumulation of starch in chloroplasts of leaves and no accumulation of starch in plastids of roots.Specifically silence the GPT1 in roots resulted in similar phenotype.Results showed that GPT1 in non-photosynthetic plastids could regulate starch metabolism in source organs,which may involve the transport and utilization of Glc-6-P as the main source of starch synthesis.In addition,on the basis of the observation of the embryos and seeds of embryo-specific GPT1 RNAi plants,it was found that the embryo development was delayed and abnormal and the seed volume was reduced as compared to the wild-type plants.Furthermore,the accumulation and distribution of lipid body were abnormal during various stages of embryonic development in embryo-specific GPT1 RNAi.Sugar produced from plant photosynthesis plays a central role to support and integrate the functions and actions of internal and external regulatory signals in driving diverse biological processes from embryogenesis to senescence.As a crucial hexose phosphate transporter,loss of function of GPT1 could lead to the reduction of transport of Glc-6-P into plastid and therefore impried OPPP pathway and NADPH production,which could result in the inhibition of starch and lipid synthesis in heterotrophic tissues.Abnormal glucose metabolism in sink organs impacts starch metabolism in source organs over a long distance,the sugar signaling molecules involved in this long-distance regulation are expected to be further studied.