Abstract
The exocyst, a eukaryotic tethering complex, coregulates targeted exocytosis as an effector of small GTPases in polarized cell growth. In land plants, several exocyst subunits are encoded by double or triple paralogs, culminating in tens of EXO70 paralogs. Out of 23 Arabidopsis thaliana EXO70 isoforms, we analyzed seven isoforms expressed in pollen. Genetic and microscopic analyses of single mutants in EXO70A2, EXO70C1, EXO70C2, EXO70F1, EXO70H3, EXO70H5, and EXO70H6 genes revealed that only a loss-of-function EXO70C2 allele resulted in a significant male-specific transmission defect (segregation 40%:51%:9%) due to aberrant pollen tube growth. Mutant pollen tubes grown in vitro exhibited an enhanced growth rate and a decreased thickness of the tip cell wall, causing tip bursts. However, exo70C2 pollen tubes could frequently recover and restart their speedy elongation, resulting in a repetitive stop-and-go growth dynamics. A pollen-specific depletion of the closest paralog, EXO70C1, using artificial microRNA in the exo70C2 mutant background, resulted in a complete pollen-specific transmission defect, suggesting redundant functions of EXO70C1 and EXO70C2. Both EXO70C1 and EXO70C2, GFP tagged and expressed under the control of their native promoters, localized in the cytoplasm of pollen grains, pollen tubes, and also root trichoblast cells. The expression of EXO70C2-GFP complemented the aberrant growth of exo70C2 pollen tubes. The absent EXO70C2 interactions with core exocyst subunits in the yeast two-hybrid assay, cytoplasmic localization, and genetic effect suggest an unconventional EXO70 function possibly as a regulator of exocytosis outside the exocyst complex. In conclusion, EXO70C2 is a novel factor contributing to the regulation of optimal tip growth of Arabidopsis pollen tubes.
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Claims 11
Claim · model-written summary
Only EXO70C2 loss of function among seven pollen isoforms caused a significant male transmission defect.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianat0 - Treatment
- loss-of-function EXO70C2 allelee0
- Gene
- EXO70C2e0
- Outcome
- male-specific transmission defecte0
- Value
- 40%:51%:9%e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“only a loss-of-function EXO70C2 allele resulted in a significant male-specific transmission defect (segregation 40%:51%:9%) due to aberrant pollen tube growth”
t0“Arabidopsis thaliana EXO70 isoforms”
Claim · model-written summary
EXO70C2 mutant pollen tubes grew faster in vitro.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Mutante0
- Outcome
- growth ratee0
- Direction
- enhancede0
- Setting
- in vitroe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mutant pollen tubes grown in vitro exhibited an enhanced growth rate”
t0“Arabidopsis thaliana EXO70 isoforms”
Claim · model-written summary
EXO70C2 mutant pollen tube tips had thinner cell walls.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Mutante1
- Outcome
- thickness of the tip cell walle0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a decreased thickness of the tip cell wall”
t0“Arabidopsis thaliana EXO70 isoforms”
e1“Mutant pollen tubes grown in vitro exhibited an enhanced growth rate”
Claim · model-written summary
EXO70C2 mutant pollen tube tips burst.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Outcome
- tip burstse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“causing tip bursts”
t0“Arabidopsis thaliana EXO70 isoforms”
Claim · model-written summary
EXO70C2 pollen tubes often recovered and resumed rapid growth, creating stop-and-go dynamics.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Material
- exo70C2e0
- Outcome
- repetitive stop-and-go growth dynamicse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exo70C2 pollen tubes could frequently recover and restart their speedy elongation, resulting in a repetitive stop-and-go growth dynamics”
t0“Arabidopsis thaliana EXO70 isoforms”
Claim · model-written summary
EXO70C1 depletion in the exo70C2 background completely blocked pollen-specific transmission.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Material
- exo70C2 mutante0
- Treatment
- pollen-specific depletione0
- Gene
- EXO70C1e0
- Outcome
- pollen-specific transmission defecte0
- Direction
- completee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A pollen-specific depletion of the closest paralog, EXO70C1, using artificial microRNA in the exo70C2 mutant background, resulted in a complete pollen-specific transmission defect”
t0“Arabidopsis thaliana EXO70 isoforms”
Claim · model-written summary
EXO70C1 and EXO70C2 were inferred to have redundant functions.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Gene
- EXO70C1 and EXO70C2e0
- Outcome
- redundant functionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“suggesting redundant functions of EXO70C1 and EXO70C2”
t0“Arabidopsis thaliana EXO70 isoforms”
Claim · model-written summary
EXO70C1 and EXO70C2 localized to cytoplasm of pollen grains, pollen tubes and root trichoblast cells.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- pollen grains, pollen tubes, and also root trichoblast cellse0
- Gene
- EXO70C1 and EXO70C2e0
- Outcome
- localized in the cytoplasme0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both EXO70C1 and EXO70C2, GFP tagged and expressed under the control of their native promoters, localized in the cytoplasm of pollen grains, pollen tubes, and also root trichoblast cells”
t0“Arabidopsis thaliana EXO70 isoforms”
Claim · model-written summary
EXO70C2-GFP expression complemented aberrant exo70C2 pollen tube growth.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- expression of EXO70C2-GFPe0
- Gene
- EXO70C2-GFPe0
- Outcome
- aberrant growthe0
- Direction
- complementede0
- Comparator
- exo70C2 pollen tubese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The expression of EXO70C2-GFP complemented the aberrant growth of exo70C2 pollen tubes”
t0“Arabidopsis thaliana EXO70 isoforms”
Claim · model-written summary
EXO70C2 did not interact with core exocyst subunits in a yeast two-hybrid assay.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Gene
- EXO70C2e0
- Outcome
- interactions with core exocyst subunitse0
- Direction
- absente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“absent EXO70C2 interactions with core exocyst subunits in the yeast two-hybrid assay”
t0“Arabidopsis thaliana EXO70 isoforms”
Claim · model-written summary
EXO70C2 was proposed to regulate exocytosis outside the exocyst complex.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Gene
- EXO70e0
- Outcome
- regulator of exocytosise0
- Qualifier
- outside the exocyst complexe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“suggest an unconventional EXO70 function possibly as a regulator of exocytosis outside the exocyst complex”
t0“Arabidopsis thaliana EXO70 isoforms”
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