Abstract
Genes directly involved in male/female and host/parasite interactions are believed to be under positive selection. The flowering plant Arabidopsis thaliana has more than 300 defensin-like (DEFL) genes, which are likely to be involved in both natural immunity and cell-to-cell communication including pollen-pistil interactions. However, little is known of the relationship between the molecular evolution of DEFL genes and their functions. Here, we identified a recently evolved cluster of DEFL genes in A. thaliana and demonstrated that these DEFL (cysteine-rich peptide [CRP810_1]) peptides, named AtLURE1 peptides, are pollen tube attractants guiding pollen tubes to the ovular micropyle. The AtLURE1 genes formed the sole species-specific cluster among DEFL genes compared to its close relative, A. lyrata. No evidence for positive selection was detected in AtLURE1 genes and their orthologs, implying neutral evolution of AtLURE1 genes. AtLURE1 peptides were specifically expressed in egg-accompanying synergid cells and secreted toward the funicular surface through the micropyle. Genetic analyses showed that gametophytic mutants defective in micropylar guidance (myb98, magatama3, and central cell guidance) do not express AtLURE1 peptides. Downregulation of the expression of these peptides impaired precise pollen tube attraction to the micropylar opening of some populations of ovules. Recombinant AtLURE1 peptides attracted A. thaliana pollen tubes at a higher frequency compared to A. lyrata pollen tubes, suggesting that these peptides are species-preferential attractants in micropylar guidance. In support of this idea, the heterologous expression of a single AtLURE1 peptide in the synergid cell of Torenia fournieri was sufficient to guide A. thaliana pollen tubes to the T. fournieri embryo sac and to permit entry into it. Our results suggest the unique evolution of AtLURE1 genes, which are directly involved in male-female interaction among the DEFL multigene family, and furthermore suggest that these peptides are sufficient to overcome interspecific barriers in gametophytic attraction and penetration.
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Claims 9
Claim · model-written summary
A recently evolved DEFL cluster was identified in A. thaliana.
- Taxon
- A. thaliana
Arabidopsis thalianae0 - Gene
- DEFL genese0
- Outcome
- recently evolved cluster of DEFL genese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we identified a recently evolved cluster of DEFL genes in A. thaliana”
Claim · model-written summary
AtLURE1 peptides guide pollen tubes to the ovular micropyle.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- AtLURE1 peptidese0
- Outcome
- guiding pollen tubes to the ovular micropylee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtLURE1 peptides, are pollen tube attractants guiding pollen tubes to the ovular micropyle”
t0“Arabidopsis”
Claim · model-written summary
AtLURE1 was the only species-specific DEFL cluster relative to A. lyrata.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- AtLURE1 genese0
- Outcome
- sole species-specific cluster among DEFL genese0
- Comparator
- A. lyratae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The AtLURE1 genes formed the sole species-specific cluster among DEFL genes compared to its close relative, A. lyrata”
t0“Arabidopsis”
Claim · model-written summary
No evidence of positive selection was found in AtLURE1 genes and their orthologs.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- AtLURE1 genese0
- Outcome
- No evidence for positive selectione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“No evidence for positive selection was detected in AtLURE1 genes and their orthologs”
t0“Arabidopsis”
Claim · model-written summary
AtLURE1 peptides were expressed in synergid cells and secreted toward the funicular surface through the micropyle.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- egg-accompanying synergid cellse0
- Gene
- AtLURE1 peptidese0
- Outcome
- specifically expressed in egg-accompanying synergid cells and secreted toward the funicular surface through the micropylee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtLURE1 peptides were specifically expressed in egg-accompanying synergid cells and secreted toward the funicular surface through the micropyle”
t0“Arabidopsis”
Claim · model-written summary
Micropylar-guidance mutants lacked AtLURE1 peptide expression.
- Taxon
- ArabidopsisArabidopsist0
- Material
- gametophytic mutantse0
- Gene
- AtLURE1 peptidese0
- Outcome
- do not express AtLURE1 peptidese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gametophytic mutants defective in micropylar guidance (myb98, magatama3, and central cell guidance) do not express AtLURE1 peptides”
t0“Arabidopsis”
Claim · model-written summary
Downregulation of AtLURE1 peptide expression impaired precise pollen tube attraction.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- Downregulation of the expression of these peptidese0
- Outcome
- precise pollen tube attraction to the micropylar openinge0
- Direction
- impairede0
- Qualifier
- some populations of ovulese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Downregulation of the expression of these peptides impaired precise pollen tube attraction to the micropylar opening of some populations of ovules”
t0“Arabidopsis”
Claim · model-written summary
Recombinant AtLURE1 peptides attracted A. thaliana pollen tubes more frequently than A. lyrata pollen tubes.
- Taxon
- A. thalianaArabidopsis thalianae0
- Treatment
- Recombinant AtLURE1 peptidese0
- Outcome
- attracted A. thaliana pollen tubese0
- Direction
- highere0
- Comparator
- A. lyrata pollen tubese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Recombinant AtLURE1 peptides attracted A. thaliana pollen tubes at a higher frequency compared to A. lyrata pollen tubes”
Claim · model-written summary
Heterologous AtLURE1 expression in Torenia fournieri synergid cells guided A. thaliana pollen tubes into its embryo sac.
- Taxon
- Torenia fournieri
Torenia fournierie0 - Organ / stage
- synergid celle0
- Treatment
- heterologous expression of a single AtLURE1 peptidee0
- Gene
- AtLURE1 peptidee0
- Outcome
- guide A. thaliana pollen tubes to the T. fournieri embryo sac and to permit entry into ite0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the heterologous expression of a single AtLURE1 peptide in the synergid cell of Torenia fournieri was sufficient to guide A. thaliana pollen tubes to the T. fournieri embryo sac and to permit entry into it”
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