Abstract
BACKGROUND: Glycosylphosphatidylinositol (GPI) addition is one of the several post-translational modifications to proteins that increase their affinity for membranes. In eukaryotes, the GPI transamidase complex (GPI-T) catalyzes the attachment of pre-assembled GPI anchors to GPI-anchored proteins (GAPs) through a transamidation reaction. A mutation in AtGPI8 (gpi8-2), the putative catalytic subunit of GPI-T in Arabidopsis, is transmitted normally through the female gametophyte (FG), indicating the FG tolerates loss of GPI transamidation. In contrast, gpi8-2 almost completely abolishes male gametophyte (MG) function. Still, the unexpected finding that gpi8-2 FGs function normally requires further investigation. Additionally, specific developmental defects in the MG caused by loss of GPI transamidation remain poorly characterized. RESULTS: Here we investigated the effect of loss of AtPIG-S, another GPI-T subunit, in both gametophytes. Like gpi8-2, we showed that a mutation in AtPIG-S (pigs-1) disrupted synergid localization of LORELEI (LRE), a putative GAP critical for pollen tube reception by the FG. Still, pigs-1 is transmitted normally through the FG. Conversely, pigs-1 severely impaired male gametophyte (MG) function during pollen tube emergence and growth in the pistil. A pPIGS:GFP-PIGS transgene complemented these MG defects and enabled generation of pigs-1/pigs-1 seedlings. However, the pPIGS:GFP-PIGS transgene seemingly failed to rescue the function of AtPIG-S in the sporophyte, as pigs-1/pigs-1, pPIGS:GFP-PIGS seedlings died soon after germination. CONCLUSIONS: Characterization of pigs-1 provided further evidence that the FG tolerates loss of GPI transamidation more than the MG and that the MG compared to the FG may be a better haploid system to study the role of GPI-anchoring. Pigs-1 pollen develops normally and thus represent a tool in which GPI anchor biosynthesis and transamidation of GAPs have been uncoupled, offering a potential way to study free GPI in plant development. While previously reported male fertility defects of GPI biosynthesis mutants could have been due either to loss of GPI or GAPs lacking the GPI anchor, our results clarified that the loss of mature GAPs underlie male fertility defects of GPI-deficient pollen grains, as pigs-1 is defective only in the downstream transamidation step.
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Claims 8
Claim · model-written summary
pigs-1 disrupted synergid localization of LORELEI.
- Taxon
- Arabidopsis
Arabidopsist0 - Treatment
- a mutation in AtPIG-S (pigs-1)e0
- Gene
- AtPIG-Se0
- Outcome
- synergid localization of LORELEI (LRE)e0
- Direction
- disruptede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a mutation in AtPIG-S (pigs-1) disrupted synergid localization of LORELEI (LRE)”
t0“Arabidopsis”
Claim · model-written summary
pigs-1 transmitted normally through the female gametophyte.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- pigs-1e0
- Outcome
- transmitted normally through the FGe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pigs-1 is transmitted normally through the FG”
t0“Arabidopsis”
Claim · model-written summary
pigs-1 severely impaired male gametophyte function during pollen tube emergence and pistil growth.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- pollen tube emergence and growth in the pistile0
- Gene
- pigs-1e0
- Outcome
- male gametophyte (MG) functione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pigs-1 severely impaired male gametophyte (MG) function during pollen tube emergence and growth in the pistil”
t0“Arabidopsis”
Claim · model-written summary
The pPIGS:GFP-PIGS transgene complemented male gametophyte defects.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- pPIGS:GFP-PIGS transgenee0
- Gene
- pPIGS:GFP-PIGSe0
- Outcome
- MG defectse0
- Direction
- complementede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A pPIGS:GFP-PIGS transgene complemented these MG defects”
t0“Arabidopsis”
Claim · model-written summary
The transgene enabled generation of homozygous pigs-1 seedlings.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- pigs-1/pigs-1e0
- Outcome
- generation of pigs-1/pigs-1 seedlingse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“enabled generation of pigs-1/pigs-1 seedlings”
t0“Arabidopsis”
Claim · model-written summary
Homozygous pigs-1 seedlings bearing pPIGS:GFP-PIGS died soon after germination.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- seedlingse0
- Gene
- pigs-1/pigs-1e0
- Outcome
- seedlings died soon after germinatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pigs-1/pigs-1, pPIGS:GFP-PIGS seedlings died soon after germination”
t0“Arabidopsis”
Claim · model-written summary
pigs-1 pollen developed normally.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- pollene0
- Gene
- Pigs-1e0
- Outcome
- pollen develops normallye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Pigs-1 pollen develops normally”
t0“Arabidopsis”
Claim · model-written summary
The authors infer that mature GPI anchored protein loss underlies male fertility defects.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- pollen grainse0
- Gene
- GAPse0
- Outcome
- male fertility defectse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the loss of mature GAPs underlie male fertility defects of GPI-deficient pollen grains”
t0“Arabidopsis”
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