ER membrane aquaporins in plants

Abstract

Plant has a large aquaporin family with more than 30 members which are divided into four subfamilies: plasma membrane intrinsic protein (PIP), tonoplast intrinsic protein (TIP), nodulin 26-like intrinsic proteins (NIP), and small and basic intrinsic proteins (SIP). Their primary structure, transport substrate, functional regulation, gene expression profile, protein amount, and intracellular localization are diversified. The SIP members have short N-terminal tails. Most aquaporins have two sets of common Asn-Pro-Ala (NPA) motif; however, the first motif of SIP1;1, SIP1;2, and SIP2;1 is changed to NPT, NPC, and NPL, respectively. SIP1;1 and SIP1;2, but not SIP2;1, have water transport activity. A recent study revealed that all three members of SIP are localized to the ER membrane and expressed in a cell specific manner in Arabidopsis thaliana. An overview is given on the main features of the SIP members in terms of their primary structure, ER membrane retention, homologues in mammals, and physiological function.

Pollen-Specific Aquaporins NIP4;1 and NIP4;2 Are Required for Pollen Development and Pollination in Arabidopsis thaliana

“…Plant AQPs are classified into seven subfamilies: plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), NOD26-like intrinsic proteins (NIPs), small basic intrinsic proteins (SIPs), X intrinsic proteins (XIPs), hybrid intrinsic proteins, and GlpF-like intrinsic proteins (Abascal et al, 2014). AQPs have been identified in most tissues of the anthers (Ruiter et al, 1997;O'Brien et al, 2002;Alexandersson et al, 2005;Bots et al, 2005a;Fujita et al, 2010) and some are pollen specific (Bock et al, 2006;Maeshima and Ishikawa, 2008;Soto et al, 2008; this study). Pollen AQPs transport water, small solutes, and/or gases during pollen development, germination, and pollen tube growth (Bock et al, 2006;Soto et al, 2008;Wudick et al, 2014).…”

Pollen vacuoles and their significance

“…They have been detected in most anther tissues (Ruiter et al 1997;O'Brien et al 2002;Alexandersson et al 2005;Bots et al 2005). Some aquaporin genes are pollen specific (Bock et al 2006;Maeshima and Ishikawa 2008;Soto et al 2008), suggesting that expression of aquaporins in pollen is under strict regulation by the gametophytic programme. Although they are likely involved in the process of water accumulation within developing vacuoles during vacuolation, the involvement of aquaporins has not yet been clearly reported in pollen development but rather in pollen germination upon contact with the stigma (Ikeda et al 1997).…”

Physiological Roles for the PIP Family of Plant Aquaporins

“…Evidence points towards regulation by changes in gene expression, protein translation and protein turnover (abundance), posttranslational, reversible modifications, intracellular changes in pH, subcellular protein targeting, recycling within membranes, and heterotetramerization (Fortin et al 1987;Morrison et al 1988;Daniels et al 1994;Kammerloher et al 1994;Robinson et al 1996;Fleurat-Lessard et al 1997;Chaumont et al 1998Chaumont et al , 2000Barkla et al 1999;Barrieu et al 1999;Cutler et al 2000;Kirch et al 2000;Verkman and Mitra 2000;Reisen et al 2003;VeraEstrella et al 2004;Ma et al 2004;Ishikawa et al 2005;Boursiac et al 2005;Prak et al 2008;Maeshina and Ishikawa 2008). By directly affecting the gating of the channel, a basis for short-term regulation exists that would allow fast fine-tuning of water or metabolite permeability.…”