Characterisation of the roles of PAM71 and PAM71HL in manganese homeostasis in chloroplasts

• Applicant: Privatdozentin Dr. Anja Schneider
• Subject Area: Plant Physiology
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 390634684

The photosynthetic water splitting takes place in a manganese-containing metal complex (the Mn cluster) embedded at the luminal side in photosystem II. By analyzing an Arabidopsis thaliana mutant with a strongly impaired photosystem II function, we could identify the membrane protein PHOTOSYNTHESIS AFFECTED MUTANT71 (PAM71), which plays a crucial role in the transport of manganese via the thylakoid membrane into the thylakoid lumen. Consequently, the pam71 mutant has less manganese available for assembling adequate amounts of the Mn cluster, impairing photosynthetic performance. PAM71 belongs to a protein family with members in plants, green algae, cyanobacteria and animals including humans. Besides PAM71, four PAM71-like proteins are found in Arabidopsis thaliana. For the closest PAM71 homolog, PAM71HL, a chloroplast localization is also predicted. Preliminary studies have shown that photosynthetic performance in the pam71hl mutant is markedly reduced and we could show that PAM71 and PAM71HL have non-redundant functions in chloroplasts. Furthermore, we identified an interaction partner of PAM71 in the thylakoid lumen. This project (I) aims to elucidate the function of PAM71HL, especially in regard to manganese homeostasis in chloroplasts. (II) Complementation studies will provide information on whether the molecular functions of PAM71, PAM71HL and their homologs from other organisms are conserved. (III) The function of PAM71 and PAM71HL in relation to manganese deficiency or stress will be examined in lines with altered PAM71/PAM71HL expression. (IV) Interaction partners of PAM71 will be characterized.

• DFG Programme: Research Grants