Annexins in the plant kingdom: perspectives and potentials
Recent advances in the field of plant annexins open a variety of new perspectives for this subfamily of annexin proteins. Ever since the first plant annexins were discovered, the majority of studies treated these proteins as "first grade" relatives of the more intensely studied vertebrate annexins. In fact, along the line there have been observations indicating otherwise, and based on the current knowledge it is quite clear that the relationship between vertebrate and plant annexins is more distant. Functionally, plant annexins have been implicated in apolar growth, growth regulation and stress response. Their expression is cell- and tissue-specific as well as developmentally regulated and their spatial distribution inside the cell agrees with that of their vertebrate relatives. On the molecular level, plant annexins behave similar to vertebrate annexins; however, distinct differences are beginning to emerge which are supported by structural findings based on two crystal structures to date. Structural insights have also revealed exciting new features, among them a putatively RedOx active motif and a loop motion in the first domain, which has been "frozen" in crystallographic snapshots of three different conformations. Based on current knowledge obtained from structural and functional studies this review discusses perspectives and potentials of the subfamily of plant annexins.