Ascorbate oxidase in plant growth, development and stress tolerance

Ascorbate oxidase (AO) is a member of the multi-copper oxidase family of enzymes and converts ascorbate to monodehydroascorbate at the same time as reducing oxygen to water. The enzyme is present in the apoplastic space of plant cells and seems to be particularly highly expressed in roots and fruits of the Cucurbitaceae family. Cell expansion and division seem to be affected by AO activity and at the whole-plant level resource allocation and yield. The enzyme is suggested to play a role in signaling between the external environment and the cell, and AO gene expression responds to wounding, plant hormones, and stress. The enzyme appears to function in plant growth and development and multiple links have been found with tolerance to abiotic and biotic stress, mostly through the use of transgenic plants. This chapter will discuss the roles of AO in plant growth, development, and stress tolerance that current research has highlighted and will also examine further roles the enzyme could play at a cellular level