Abstract
Karrikins (KARs) are chemicals in smoke that can enhance germination of many plants. Lettuce (Lactuca sativa) cv. Grand Rapids germinates in response to nanomolar karrikinolide (KAR1). Lettuce is much less responsive to KAR2 or a mixture of synthetic strigolactone analogs, rac-GR24. We investigated the molecular basis of selective and sensitive KAR1 perception in lettuce. The lettuce genome contains two copies of KARRIKIN INSENSITIVE2 (KAI2), which in Arabidopsis (Arabidopsis thaliana) encodes a receptor that is required for KAR responses. LsKAI2b is more highly expressed than LsKAI2a in dry achenes and during early stages of imbibition. Through cross-species complementation assays in Arabidopsis, we found that an LsKAI2b transgene confers robust responses to KAR1, but LsKAI2a does not. Therefore, LsKAI2b likely mediates KAR1 responses in lettuce. We compared homology models of KAI2 proteins from lettuce and a fire-follower, whispering bells (Emmenanthe penduliflora). This identified pocket residues 96, 124, 139, and 161 as candidates that influence the ligand specificity of KAI2. Further support for the importance of these residues was found through a broader comparison of pocket residues among 281 KAI2 proteins from 184 asterid species. Almost all KAI2 proteins had either Tyr or Phe identity at position 124. Genes encoding Y124-type KAI2 are more broadly distributed in asterids than in F124-type KAI2. Substitutions at residues 96, 124, 139, and 161 in Arabidopsis KAI2 produced a broad array of responses to KAR1, KAR2, and rac-GR24. This suggests that the diverse ligand preferences observed among KAI2 proteins in plants could have evolved through relatively few mutations.
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Claims 13
Claim · model-written summary
Grand Rapids lettuce germinated in response to nanomolar KAR1.
- Taxon
- Lettuce
Lactuca sativae0 - Material
- cv. Grand Rapidse0
- Treatment
- nanomolar karrikinolide (KAR1)e0
- Outcome
- germinatese0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lettuce (Lactuca sativa) cv. Grand Rapids germinates in response to nanomolar karrikinolide (KAR1).”
Claim · model-written summary
Lettuce was less responsive to KAR2 than to KAR1.
- Taxon
- LettuceLactuca sativae0
- Treatment
- KAR2e0
- Outcome
- responsivee0
- Direction
- much less responsivee0
- Comparator
- KAR1e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lettuce is much less responsive to KAR2 or a mixture of synthetic strigolactone analogs, rac-GR24.”
e1“Lettuce (Lactuca sativa) cv. Grand Rapids germinates in response to nanomolar karrikinolide (KAR1).”
Claim · model-written summary
Lettuce was less responsive to rac-GR24 than to KAR1.
- Taxon
- LettuceLactuca sativae0
- Treatment
- rac-GR24e0
- Outcome
- responsivee0
- Direction
- much less responsivee0
- Comparator
- KAR1e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lettuce is much less responsive to KAR2 or a mixture of synthetic strigolactone analogs, rac-GR24.”
e1“Lettuce (Lactuca sativa) cv. Grand Rapids germinates in response to nanomolar karrikinolide (KAR1).”
Claim · model-written summary
The lettuce genome contains two KAI2 copies.
- Taxon
- lettuceLactuca sativae0
- Gene
- KARRIKIN INSENSITIVE2 (KAI2)e0
- Outcome
- two copies of KARRIKIN INSENSITIVE2 (KAI2)e0
- Value
- two copiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The lettuce genome contains two copies of KARRIKIN INSENSITIVE2 (KAI2)”
Claim · model-written summary
LsKAI2b was more highly expressed than LsKAI2a in dry achenes and early imbibition.
- Taxon
- lettuceLactuca sativae1
- Organ / stage
- dry achenese0
- Gene
- LsKAI2be0
- Outcome
- LsKAI2b is more highly expressede0
- Direction
- more highlye0
- Comparator
- LsKAI2ae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“LsKAI2b is more highly expressed than LsKAI2a in dry achenes and during early stages of imbibition.”
e1“The lettuce genome”
Claim · model-written summary
An LsKAI2b transgene conferred robust KAR1 responses in Arabidopsis.
- Taxon
- Arabidopsis
Arabidopsise0 - Treatment
- an LsKAI2b transgenee0
- Gene
- LsKAI2be0
- Outcome
- robust responses to KAR1e0
- Comparator
- LsKAI2ae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Through cross-species complementation assays in Arabidopsis, we found that an LsKAI2b transgene confers robust responses to KAR1, but LsKAI2a does not.”
Claim · model-written summary
An LsKAI2a transgene did not confer robust KAR1 responses in Arabidopsis.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Through cross-species complementation assays in Arabidopsis, we found that an LsKAI2b transgene confers robust responses to KAR1, but LsKAI2a does not.”
Claim · model-written summary
The authors infer that LsKAI2b likely mediates KAR1 responses in lettuce.
- Taxon
- lettuceLactuca sativae0
- Gene
- LsKAI2be0
- Outcome
- KAR1 responsese0
- Qualifier
- likely mediatese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Therefore, LsKAI2b likely mediates KAR1 responses in lettuce.”
Claim · model-written summary
KAI2 pocket residues 96, 124, 139 and 161 were candidate determinants of ligand specificity.
- Taxon
- lettuceLactuca sativae0
- Gene
- KAI2e0
- Outcome
- pocket residues 96, 124, 139, and 161 as candidates that influence the ligand specificity of KAI2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We compared homology models of KAI2 proteins from lettuce and a fire-follower, whispering bells (Emmenanthe penduliflora). This identified pocket residues 96, 124, 139, and 161 as candidates that influence the ligand specificity of KAI2.”
Claim · model-written summary
Almost all surveyed KAI2 proteins carried Tyr or Phe at residue 124.
Verbatim
e0“Almost all KAI2 proteins had either Tyr or Phe identity at position 124.”
e1“281 KAI2 proteins from 184 asterid species”
Claim · model-written summary
Y124-type KAI2 genes were more broadly distributed in asterids than F124-type genes.
Verbatim
e0“Genes encoding Y124-type KAI2 are more broadly distributed in asterids than in F124-type KAI2.”
Claim · model-written summary
Substituting four KAI2 residues in Arabidopsis produced diverse responses to three ligands.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- Substitutions at residues 96, 124, 139, and 161e0
- Gene
- KAI2e0
- Outcome
- a broad array of responses to KAR1, KAR2, and rac-GR24e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Substitutions at residues 96, 124, 139, and 161 in Arabidopsis KAI2 produced a broad array of responses to KAR1, KAR2, and rac-GR24.”
Claim · model-written summary
The authors suggest diverse KAI2 ligand preferences could evolve through few mutations.
- Taxon
- plantsViridiplantaee0
- Gene
- KAI2e0
- Outcome
- diverse ligand preferencese0
- Qualifier
- relatively few mutationse0
Verbatim
e0“This suggests that the diverse ligand preferences observed among KAI2 proteins in plants could have evolved through relatively few mutations.”
The same questions in other papers
nanoparticle · growth · Lactuca sativa (garden lettuce)Positive and negative results
20 papers in the same direction as this paper · 6 in the opposite direction
- no effect
- negative
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See all 27 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.