FRET imaging in living maize cells reveals that plasma membrane aquaporins interact to regulate their subcellular localization

Abstract

Zea mays plasma membrane intrinsic proteins (ZmPIPs) fall into two groups, ZmPIP1s and ZmPIP2s, that exhibit different water channel activities when expressed in Xenopus oocytes. ZmPIP1s are inactive, whereas ZmPIP2s induce a marked increase in the membrane osmotic water permeability coefficient, P f. We previously showed that, in Xenopus oocytes, ZmPIP1;2 and ZmPIP2;1 interact to increase the cell Pf. Here, we report the localization and interaction of ZmPIP1s and ZmPIP2s in living maize cells. ZmPIPs were fused to monomeric yellow fluorescent protein and/or monomeric cyan fluorescent protein and expressed transiently in maize mesophyll protoplasts. When expressed alone, ZmPIP1 fusion proteins were retained in the endoplasmic reticulum, whereas ZmPIP2s were found in the plasma membrane. Interestingly, when coexpressed with ZmPIP2s, ZmPIP1s were relocalized to the plasma membrane. Using FRET/fluorescence lifetime imaging microscopy, we demonstrated that this relocalization results from interaction between ZmPIP1s and ZmPIP2s. Immunoprecipitation experiments provided additional evidence for the association of ZmPIP1;2 and ZmPIP2;1 in maize roots and suspension cells. These data suggest that PIP1-PIP2 interaction is required for in planta PIP1 trafficking to the plasma membrane to modulate plasma membrane permeability.protein interaction ͉ trafficking ͉ Zea mays plasma membrane intrinsic protein

Proteomic changes in maize as a response to heavy metal (lead) stress revealed by iTRAQ quantitative proteomics

“…Moreover, coexpression of nonfunctional ZmPIP1;1 and ZmPIP1;2 isoforms with functional ZmPIP2 protein could enhance their aquaporin activity significantly in maize (Fetter et al, 2004). Further study suggested that PIP1 trafficking would be required for the plasma membrane by PIP1-PIP2 interaction, thereby modulating plasma membrane permeability (Zelazny et al, 2007). We demonstrated that PIPs might facilitate the transport of molecules by modulating plasma membrane permeability in response to Pb pollution.…”

Barley plasma membrane intrinsic proteins (PIP Aquaporins) as water and CO2 transporters

“…Interactions between ZmPIP1s and ZmPIP2s were clearly demonstrated in living maize cells using a FRET imaging system [31]. At present, however, there is no information suggesting whether heteromerization regulation is or is not involved in the regulation of aquaporin activity and cellular water transport in plant cells under salt or osmotic stress.…”

Aquaporin structure–function relationships: Water flow through plant living cells

“…The accumulation of transcripts arising from NgMIP2, NgMIP3 and NgMIP4 diminished dramatically in drought-stressed plants. This down-regulation of MIP gene expression may result in reduced membrane water permeability and may encourage cellular water conservation during periods of dehydration stress [116,122,123].…”

“…There is growing evidence that suggests that aquaporins play different roles throughout plant development [120][121][122][123][124][125]. Therefore, aquaporin genomic information is important because, assigning physiological function via transgenic reduction or removal of gene expression requires sequence information for precise targeting.…”

“…Direct determination of the location of each aquaporin within tissues is still required to understand its function in the plant. A powerful tool in elucidating the aquaporin function is given by the reverse genetics that can also reveal unexpected function of water channel proteins, which benefit to our understanding of sequence-structure and structure-function relationships in plants [2,4,5,9,121,122]. This should be done both at the transcript and at the protein level because aquaporin turnover appears to be variable, such as when comparing constitutively expressed and inducible aquaporins.…”