Novel type aquaporin SIPs are mainly localized to the ER membrane and show cell‐specific expression in <i>Arabidopsis thaliana</i>

Ishikawa, Fumiyoshi; Suga, Shinobu; Uemura, Tomohiro; Sato, Masa H.; Maeshima, Masayoshi

doi:10.1016/j.febslet.2005.09.076

Cited by 183 publications

(148 citation statements)

References 34 publications

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“…Similar to what was observed in pollen, we detected a consistent, intracellular PIN8-GFP signal co-localized with ER markers, such as BIP2 (ref. 28) in root cells ( Fig. 3d-f, p).…”

Section: Pin8 Is Expressed and Functions In The Male Gametophytementioning

confidence: 90%

ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

et al. 2012

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Auxin is a key coordinative signal required for many aspects of plant development and its levels are controlled by auxin metabolism and intercellular auxin transport. Here we find that a member of PIn auxin transporter family, PIn8 is expressed in male gametophyte of Arabidopsis thaliana and has a crucial role in pollen development and functionality. Ectopic expression in sporophytic tissues establishes a role of PIn8 in regulating auxin homoeostasis and metabolism. PIn8 co-localizes with PIn5 to the endoplasmic reticulum (ER) where it acts as an auxin transporter. Genetic analyses reveal an antagonistic action of PIn5 and PIn8 in the regulation of intracellular auxin homoeostasis and gametophyte as well as sporophyte development. our results reveal a role of the auxin transport in male gametophyte development in which the distinct actions of ER-localized PIn transporters regulate cellular auxin homoeostasis and maintain the auxin levels optimal for pollen development and pollen tube growth.

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“…Similar to what was observed in pollen, we detected a consistent, intracellular PIN8-GFP signal co-localized with ER markers, such as BIP2 (ref. 28) in root cells ( Fig. 3d-f, p).…”

Section: Pin8 Is Expressed and Functions In The Male Gametophytementioning

confidence: 90%

ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

et al. 2012

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“…subfamily), and it has been suggested that they are glycerol (MIP1) or water and glycerol (MIP2) transporters. MIP3 exhibits the greatest similarity to plant small basic intrinsic proteins (SIPs) (31), which generally are localized in the plant endoplasmic reticulum (ER) membrane (32). MIP1 and MIP3 were readily detected using reverse transcription-PCR, indicating that MIP2 is expressed only weakly, if at all, in our culture conditions.…”

Section: Osmoregulation Inmentioning

confidence: 90%

The Contractile Vacuole as a Key Regulator of Cellular Water Flow in Chlamydomonas reinhardtii

2014

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Most freshwater flagellates use contractile vacuoles (CVs) to expel excess water. We have used Chlamydomonas reinhardtii as a green model system to investigate CV function during adaptation to osmotic changes in culture medium. We show that the contractile vacuole in Chlamydomonas is regulated in two different ways. The size of the contractile vacuoles increases during cell growth, with the contraction interval strongly depending on the osmotic strength of the medium. In contrast, there are only small fluctuations in cytosolic osmolarity and plasma membrane permeability. Modeling of the CV membrane permeability indicates that only a small osmotic gradient is necessary for water flux into the CV, which most likely is facilitated by the aquaporin major intrinsic protein 1 (MIP1). We show that MIP1 is localized to the contractile vacuole, and that the expression rate and protein level of MIP1 exhibit only minor fluctuations under different osmotic conditions. In contrast, SEC6, a protein of the exocyst complex that is required for the water expulsion step, and a dynamin-like protein are upregulated under strong hypotonic conditions. The overexpression of a CreMIP1-GFP construct did not change the physiology of the CV. The functional implications of these results are discussed. In hypotonic media, cells/organisms take up water by osmosis. Water uptake occurs only if the water potential inside the cell is more negative than that outside the cell. The amount of water taken up in a given time depends on (i) the water potential gradient between the medium and the cell interior, (ii) the surface area of the plasma membrane (PM), and (iii) the extent to which the PM is permeable to water. Cells can use three strategies to prevent bursting caused by the osmotic influx of water in a hypotonic environment. First, organisms can modify the composition of its interior, its surface area, and/or its PM permeability to limit water uptake. Second, organisms can use a cell wall to generate a cell wall pressure potential (turgor) to balance the osmotic water potential, as many algae, plants, and fungi do. However, many unicellular protists do not possess a rigid cell wall. Instead, these protists use a third strategy: they employ water pumps called contractile vacuoles (CVs) to remove excess water. CVs are specialized vacuoles that slowly accumulate water during diastole and periodically expel the liquid rapidly into the medium (systole) (1-4).Although CV morphologies and behaviors differ among various organisms (see for a recent comparison of the contractile vacuoles of a variety of protists), the basic mechanism (water uptake into the CV by osmosis) appears to be conserved between different eukaryotes. The same proteins/ cellular processes have been implicated in CV function in Amoeba, Dictyostelium, Paramecium, Trypanosoma, and green algae (e.g., proton pumps and aquaporins) (3, 4, 6). However, we still do not know anything about what other factors (ion transport systems) are needed to build up the necessary osmotic gradient in a...

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“…We compared the fluorescent patterns of various markers (Figures 5A to 5G; see Supplemental Movie 1 online) with that of CHX23-GFP ( Figure 5H; see Supplemental Movie 2 online) and found that the CHX23-GFP signal was similar to that of an ER membrane-bound protein, SIP2. 1-GFP (Ishikawa et al, 2005) (Figure 5E), and an ER lumen protein, GFP-HDEL ( Figure 5F; see Supplemental Movie 1 online). To verify this possibility, tobacco pollen was cotransfected with CHX23-RFP and SIP2.1-GFP or GFP-HDEL.…”

Section: Chx23 Is Localized To Endomembranes Resembling Er In Growingmentioning

confidence: 99%

“…For each bombardment, 1.25 mg DNA and 7 mg tobacco pollen were used. Pollen was transfected with NtPLIM2b-GFP , GFP-Rab2 , GFP-Rab5, mito-GFP, GFP-HDEL (Cheung and Wu, 2007), SIP2.1-GFP (Ishikawa et al, 2005;A. Cheung and H. Wu, unpublished data), and LAT52:GFP (Cheung, 2001) to visualize actin filament, Golgi, endosome, mitochondria, ER, and cytosol, respectively.…”

Section: Plant or Pollen Transformationmentioning

confidence: 99%

Pollen Tubes Lacking a Pair of K+ Transporters Fail to Target Ovules inArabidopsis

et al. 2011

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Flowering plant reproduction requires precise delivery of the sperm cells to the ovule by a pollen tube. Guidance signals from female cells are being identified; however, how pollen responds to those cues is largely unknown. Here, we show that two predicted cation/proton exchangers (CHX) in Arabidopsis thaliana, CHX21 and CHX23, are essential for pollen tube guidance. Male fertility was unchanged in single chx21 or chx23 mutants. However, fertility was impaired in chx21 chx23 double mutant pollen. Wild-type pistils pollinated with a limited number of single and double mutant pollen producing 62% fewer seeds than those pollinated with chx23 single mutant pollen, indicating that chx21 chx23 pollen is severely compromised. Double mutant pollen grains germinated and grew tubes down the transmitting tract, but the tubes failed to turn toward ovules. Furthermore, chx21 chx23 pollen tubes failed to enter the micropyle of excised ovules. Green fluorescent protein-tagged CHX23 driven by its native promoter was localized to the endoplasmic reticulum of pollen tubes. CHX23 mediated K + transport, as CHX23 expression in Escherichia coli increased K + uptake and growth in a pH-dependent manner. We propose that by modifying localized cation balance and pH, these transporters could affect steps in signal reception and/or transduction that are critical to shifting the axis of polarity and directing pollen growth toward the ovule.

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Novel type aquaporin SIPs are mainly localized to the ER membrane and show cell‐specific expression in Arabidopsis thaliana

Cited by 183 publications

References 34 publications

ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

The Contractile Vacuole as a Key Regulator of Cellular Water Flow in Chlamydomonas reinhardtii

Pollen Tubes Lacking a Pair of K+ Transporters Fail to Target Ovules inArabidopsis

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