Abstract

There are eight annexin genes in the model species Arabidopsis thaliana. Annexins are thought to have diverse roles ranging from hydrolysis of ATP and GTP , cation channel formation and regulation, to exocytosis and cell cycle control. Plant annexins are able to bind intracellular calcium with an endonexin fold within a five α helical annexin repeat and have been discovered in a number of cellular compartments in various species and tissues. A. thaliana Annexin 1 (ANNAt1) is highly expressed in the roots and increases in expression levels of ANN At1 have been recorded in response to drought, salinity, cold, heat and heavy metal stress. To date ANN At1 has been experimentally shown to function as a plasma membrane calcium and potassium conductive protein, activated by hydroxyl radicals (in lipid bilayers) and salt stress (epidermal protoplasts) implicating the protein in sodicity signalling. Reactive oxygen species activated calcium channels also function in growth, indicating ANN At1 may function in this essential pathway.