Aquaporins in the plant kingdom: the regulatory mechanisms revisited

Abstract

More than 30 years ago, biophysicist and animal physiologists supported the hypothesis of the existence of pores facilitating water transport through membranes since certain animal structures were unusually permeable to water. Although plant physiologists also discussed the existence of water channels since the early 1960s, the survey remained marginal in the field (reviewed by Chrispeels and Maurel 1994). It was in 1992 that the hypothetical proteinaceous water channel was identified (named CHIP28, now AQP1) by Preston et. al. This discovery opened the molecular detection of homologous proteins in all kingdoms. The term “aquaporins” (AQPs) was suggested later, when other two proteins belonging to the MIP26 family (WCH-CD -from mammalian collecting ductand g-TIP -from tonoplast of Arabidopsis thaliana-) were also characterized as water channels (Agre et al., 1993). The first cloned and functionally expressed aquaporin from plants was therefore g-TIP (now TIP1;1) (Maurel et al., 1993). Since this event, plant aquaporins captured significant attention. This article intends to explore the regulatory mechanisms in plant aquaporins and to contrast them with those achievements made on their animal homologues. The aim is to merge the contributions made by both fields of research.