Are plant annexins new components of protein complexes at membrane contact sites?

Annexins, as cytosolic and membrane-associated proteins, are essential for cellular processes in a wide range of eukaryotic organisms, spanning from humans to plants. They can bind calcium ions, phospholipids and cytoskeletal components, and thus play a crucial role in membrane organization, dynamics and trafficking, as well as in development and environmental stress responses of eukaryotes. A relatively new concept suggests that animal annexins AnxA6 and AnxA1 participate in protein complexes with other proteins, such as Drp1, Rab GTPase 7, TBC1D15, or FIS1, that are important for the establishment and function of membrane contact sites (MCSs) between several subcellular compartments. Plant annexins show diverse subcellular localizations, including putative MCSs between organelles, but their participation in MCS protein complexes is unknown. Despite limited homology with the MCS-localized animal annexins AnxA6 and AnxA1, bioinformatic analyses, AlphaFold-Multimer modelling and fluorescence confocal microscopy support a possible role for Arabidopsis annexins in MCS formation and function. All eight Arabidopsis annexins are predicted to have FFAT motifs that may be potentially important for MCSs formation between endoplasmic reticulum and other organelles. Moreover, there are plant dynamin, Rab GTPase, TBC1D15, and FIS1 and VAMP homologs, which might form functional complexes with some plant annexins in MCSs. This update provides a new perspective on plant annexins, presenting them as new putative players in protein complexes important for organellar interactions in MCSs.