Gamete Attachment Requires GEX2 for Successful Fertilization in Arabidopsis

Mori, Toshiyuki; Igawa, Tomoko; Tamiya, Gen; Miyagishima, Shin-ya; Berger, Frédéric

doi:10.1016/j.cub.2013.11.030

Cited by 117 publications

(122 citation statements)

References 28 publications

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“…Thus, adhesion depends on species-limited proteins, whereas merger uses broadly conserved HAP2. This new concept in fertilization has since been confirmed in Arabidopsis and Tetrahymena (Sprunck et al, 2012;Cole et al, 2014;Mori et al, 2014;Dresselhaus and Snell, 2014).…”

Section: Introductionmentioning

confidence: 83%

The cytoplasmic domain of the gamete membrane fusion protein HAP2 targets the protein to the fusion site in Chlamydomonas and regulates the fusion reaction

et al. 2015

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Cell-cell fusion between gametes is a defining step during development of eukaryotes, yet we know little about the cellular and molecular mechanisms of the gamete membrane fusion reaction. HAP2 is the sole gamete-specific protein in any system that is broadly conserved and shown by gene disruption to be essential for gamete fusion. The wide evolutionary distribution of HAP2 (also known as GCS1) indicates it was present in the last eukaryotic common ancestor and, therefore, dissecting its molecular properties should provide new insights into fundamental features of fertilization. HAP2 acts at a step after membrane adhesion, presumably directly in the merger of the lipid bilayers. Here, we use the unicellular alga Chlamydomonas to characterize contributions of key regions of HAP2 to protein location and function. We report that mutation of three strongly conserved residues in the ectodomain has no effect on targeting or fusion, although short deletions that include those residues block surface expression and fusion. Furthermore, HAP2 lacking a 237-residue segment of the cytoplasmic region is expressed at the cell surface, but fails to localize at the apical membrane patch specialized for fusion and fails to rescue fusion. Finally, we provide evidence that the ancient HAP2 contained a juxta-membrane, multicysteine motif in its cytoplasmic region, and that mutation of a cysteine dyad in this motif preserves protein localization, but substantially impairs HAP2 fusion activity. Thus, the ectodomain of HAP2 is essential for its surface expression, and the cytoplasmic region targets HAP2 to the site of fusion and regulates the fusion reaction.

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Section: Introductionmentioning

confidence: 83%

The cytoplasmic domain of the gamete membrane fusion protein HAP2 targets the protein to the fusion site in Chlamydomonas and regulates the fusion reaction

et al. 2015

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“…27 Later work revealed that the BSG protein also acts during sperm interactions with the cumulus cells and the zona pellucida. 28 Arabidopsis and Chlamydomonas have GEX2 29,30 and FUS1, 31,32 respectively, both of which are single-pass TM proteins with Ig-like filamin repeat domains. These two proteins are involved in gamete fusion or attachment.…”

Section: Ig-like Domains Play Key Roles During Gamete Interactions Inmentioning

confidence: 99%

Gamete interactions require transmembranous immunoglobulin-like proteins with conserved roles during evolution

Nishimura

L’Hernault

2016

Worm

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C. elegans spe-9 class genes are male germline-enriched in their expression and indispensable during sperm-oocyte fusion. Identification of mammalian orthologs that exhibit similar functions to these C. elegans genes has been a challenge. The mouse Izumo1 gene encodes a sperm-specific, immunoglobulin (Ig)-like transmembrane (TM) protein that is required for gamete fusion. We recently identified the C. elegans spe-45 gene, which shows male germline-enriched expression and encodes an Ig-like TM protein. spe-45 mutant worms produced otherwise normal spermatozoa that cannot fuse with oocytes, causing essentially the same phenotype as that seen in the Izumo1-knockout mice. By counting the number of self-sperm in the spermatheca of spe-45 hermaphrodites, it was found that this gene might be involved in sperm guidance from the uterus into the spermatheca, as well as gamete fusion. Moreover, we discovered that SPE-45 and IZUMO1 share certain functions for gamete fusion, which are presumably related to binding with cis-and/or trans-partners. Intriguingly, various organisms have Ig-like TM proteins that act during gamete interactions, indicating the wide-spread utility of Ig-like domains during fertilization.

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“…To identify these factors, Mori and colleagues performed a new experiment using Arabidopsis gametic marker lines. 5 …”

Section: Fertilization Mechanisms Reside On the Gamete Surface Of Flomentioning

confidence: 99%

Gamete attachment process revealed in flowering plant fertilization

Mori

Igawa

2014

Plant Signaling & Behavior

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Gamete Attachment Requires GEX2 for Successful Fertilization in Arabidopsis

Cited by 117 publications

References 28 publications

The cytoplasmic domain of the gamete membrane fusion protein HAP2 targets the protein to the fusion site in Chlamydomonas and regulates the fusion reaction

The cytoplasmic domain of the gamete membrane fusion protein HAP2 targets the protein to the fusion site in Chlamydomonas and regulates the fusion reaction

Gamete interactions require transmembranous immunoglobulin-like proteins with conserved roles during evolution

Gamete attachment process revealed in flowering plant fertilization

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