The aim of this study is to identify and functionally characterizesolute transporters from the chloroplast thylakoid membrane ofArabidopsis thaliana. As compared to chloroplast envelope transporters,much less information is available for transport processesacross the thylakoid membrane, which is mostly studied as thesite of light-driven photosynthetic reactions coupled to ATP synthesis.Although there are many reported examples of transportactivities, only a few thylakoid transporters have been identifiedat the gene level. Using bioinformatics analyses, we have predictedthe existence of approx. fifteen thylakoid transporters. Forexperimental validation, we have carried out immuno-localizationstudies used peptide-specific antibodies, functional analyses inheterologous system and validation using knockout mutants. Wehave recently identified one ATP/ADP carrier (Thuswaldneret al. JBC 2007) and one Na(+)-dependent phosphate transporter(Ruiz Pavon et al. JBC 2008). They are proposed to participatein the nucleotide metabolism in the thylakoid lumen(Spetea et al. PNAS 20004) as well as to balance the transthylakodproton electrochemical gradient storage. Based on phenotypicanalyses of knockout mutants, we will present novel dataabout the key physiological role of the two transporters duringthe high-light-induced repair of photosystem II complex in thethylakoid membrane. Subsequently, we will make a survey on theoutlook of thylakoid activities awaiting identification of responsibleproteins. Such knowledge is necessary to understand the thylakoidnetwork of transporters, and its role in photosynthesisand adaptation to environmental stress.