Abstract
Serration found along leaf margins shows species-specific characters. Whereas compound leaf development is well studied, the process of serration formation is largely unknown. To understand mechanisms of serration development, we investigated distinctive features of cells that could give rise to tooth protrusion in the simple-leaf plant Arabidopsis. After the emergence of a tooth, marginal cells, except for cells at the sinuses and tips, started to elongate rapidly. Localized cell division seemed to keep cells at the sinus smaller, rather than halt cell elongation. As leaves matured, the marginal cell number between teeth became similar in any given tooth. These results suggest that teeth are formed by repetition of an unknown mechanism that spatially monitors cell number and regulates cell division. We then examined the role of CUP-SHAPED COTYLEDON 2 (CUC2) in serration development. cuc2-3 forms fewer hydathodes and auxin maxima, visualized by DR5rev::GFP, at the leaf margin, suggesting that CUC2 patterns serration through the regulation of auxin. In contrast to a previous interpretation, comparison of leaf outlines revealed that CUC2 promotes outgrowth of teeth rather than suppression of growth at the sinuses. We found that mutants with increased CUC2 expression form ectopic tissues and mis-express SHOOT MERISTEMLESS (STM) at the sinus between the enhanced teeth. Similar but infrequent STM expression was found in the wild type, indicating STM involvement in the serration of simple leaves. Our study provides insights into the morphological and molecular mechanisms for leaf development and tooth formation, and highlights similarities between serration and compound leaf development.
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Claims 11
Claim · model-written summary
After tooth emergence, marginal cells except sinus and tip cells elongate rapidly.
- Taxon
- Arabidopsis
Arabidopsist0 - Organ / stage
- marginal cellse0
- Outcome
- elongate rapidlye0
- Direction
- elongate rapidlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After the emergence of a tooth, marginal cells, except for cells at the sinuses and tips, started to elongate rapidly.”
t0“Arabidopsis”
Claim · model-written summary
Localized division appears to keep sinus cells smaller.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- cells at the sinus smallere0
- Qualifier
- Localized cell divisione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Localized cell division seemed to keep cells at the sinus smaller, rather than halt cell elongation.”
t0“Arabidopsis”
Claim · model-written summary
Marginal cell numbers between teeth became similar as leaves matured.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- marginal cell number between teethe0
- Direction
- became similare0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As leaves matured, the marginal cell number between teeth became similar in any given tooth.”
t0“Arabidopsis”
Claim · model-written summary
The authors infer repeated spatial monitoring of cell number and regulation of cell division during tooth formation.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- teeth are formede0
- Qualifier
- spatially monitors cell number and regulates cell divisione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“teeth are formed by repetition of an unknown mechanism that spatially monitors cell number and regulates cell division.”
t0“Arabidopsis”
Claim · model-written summary
cuc2-3 forms fewer leaf margin hydathodes and auxin maxima.
- Taxon
- ArabidopsisArabidopsist0
- Material
- cuc2-3e0
- Outcome
- hydathodes and auxin maximae0
- Direction
- fewere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cuc2-3 forms fewer hydathodes and auxin maxima, visualized by DR5rev::GFP, at the leaf margin”
t0“Arabidopsis”
Claim · model-written summary
CUC2 is inferred to pattern serration through auxin regulation.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- CUC2e0
- Compound
- auxine0
- Outcome
- serratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“suggesting that CUC2 patterns serration through the regulation of auxin.”
t0“Arabidopsis”
Claim · model-written summary
CUC2 promotes tooth outgrowth.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- CUC2e0
- Outcome
- outgrowth of teethe0
- Direction
- promotese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CUC2 promotes outgrowth of teeth rather than suppression of growth at the sinuses.”
t0“Arabidopsis”
Claim · model-written summary
Mutants with increased CUC2 expression form ectopic tissues.
- Taxon
- ArabidopsisArabidopsist0
- Material
- mutantse0
- Gene
- CUC2e0
- Outcome
- ectopic tissuese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mutants with increased CUC2 expression form ectopic tissues and mis-express SHOOT MERISTEMLESS (STM) at the sinus between the enhanced teeth.”
t0“Arabidopsis”
Claim · model-written summary
Mutants with increased CUC2 expression mis-express STM at the sinus.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- sinuse0
- Gene
- SHOOT MERISTEMLESS (STM)e0
- Outcome
- mis-expresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mutants with increased CUC2 expression form ectopic tissues and mis-express SHOOT MERISTEMLESS (STM) at the sinus between the enhanced teeth.”
t0“Arabidopsis”
Claim · model-written summary
STM expression also occurs infrequently in wild type.
- Taxon
- ArabidopsisArabidopsist0
- Material
- wild typee0
- Gene
- STMe0
- Outcome
- STM expressione0
- Qualifier
- infrequente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Similar but infrequent STM expression was found in the wild type”
t0“Arabidopsis”
Claim · model-written summary
The authors infer STM involvement in simple-leaf serration.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- STMe0
- Outcome
- serration of simple leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“indicating STM involvement in the serration of simple leaves.”
t0“Arabidopsis”