Abstract
The plant hormone indole-3-acetic acid (IAA or auxin) mediates the elongation growth of shoot tissues by promoting cell expansion. According to the acid growth theory proposed in the 1970s, auxin activates plasma membrane H+-ATPases (PM H+-ATPases) to facilitate cell expansion by both loosening the cell wall through acidification and promoting solute uptake. Mechanistically, however, this process is poorly understood. Recent findings in Arabidopsis (Arabidopsis thaliana) have demonstrated that auxin-induced SMALL AUXIN UP RNA (SAUR) genes promote elongation growth and play a key role in PM H+-ATPase activation by inhibiting PP2C.D family protein phosphatases. Here, we extend these findings by demonstrating that SAUR proteins also inhibit tomato PP2C.D family phosphatases and that AtSAUR19 overexpression in tomato (Solanum lycopersicum) confers the same suite of phenotypes as previously reported for Arabidopsis. Furthermore, we employ a custom image-based method for measuring hypocotyl segment elongation with high resolution and a method for measuring cell wall mechanical properties, to add mechanistic details to the emerging description of auxin-mediated cell expansion. We find that constitutive expression of GFP-AtSAUR19 bypasses the normal requirement of auxin for elongation growth by increasing the mechanical extensibility of excised hypocotyl segments. In contrast, hypocotyl segments overexpressing a PP2C.D phosphatase are specifically impaired in auxin-mediated elongation. The time courses of auxin-induced SAUR expression and auxin-dependent elongation growth were closely correlated. These findings indicate that induction of SAUR expression is sufficient to elicit auxin-mediated expansion growth by activating PM H+-ATPases to facilitate apoplast acidification and mechanical wall loosening.
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Claims 7
Claim · model-written summary
SAUR proteins inhibited tomato PP2C.D family phosphatases.
- Taxon
- Tomato
Solanum lycopersicumt0 - Gene
- SAUR proteinse0
- Outcome
- inhibit tomato PP2C.D family phosphatasese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SAUR proteins also inhibit tomato PP2C.D family phosphatases”
t0“Tomato”
Claim · model-written summary
AtSAUR19 overexpression conferred the previously reported Arabidopsis phenotype suite in tomato.
- Taxon
- TomatoSolanum lycopersicumt0
- Treatment
- AtSAUR19 overexpressione0
- Gene
- AtSAUR19e0
- Outcome
- same suite of phenotypese0
- Comparator
- Arabidopsise0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtSAUR19 overexpression in tomato (Solanum lycopersicum) confers the same suite of phenotypes as previously reported for Arabidopsis”
t0“Tomato”
Claim · model-written summary
Constitutive GFP-AtSAUR19 expression bypassed auxin requirement for elongation growth.
- Taxon
- TomatoSolanum lycopersicumt0
- Organ / stage
- hypocotyl segmentse0
- Treatment
- constitutive expression of GFP-AtSAUR19e0
- Gene
- GFP-AtSAUR19e0
- Outcome
- elongation growthe0
- Direction
- bypassese0
- Comparator
- normal requirement of auxine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“constitutive expression of GFP-AtSAUR19 bypasses the normal requirement of auxin for elongation growth by increasing the mechanical extensibility of excised hypocotyl segments”
t0“Tomato”
Claim · model-written summary
Constitutive GFP-AtSAUR19 expression increased mechanical extensibility of excised hypocotyl segments.
- Taxon
- TomatoSolanum lycopersicumt0
- Treatment
- constitutive expression of GFP-AtSAUR19e0
- Gene
- GFP-AtSAUR19e0
- Outcome
- mechanical extensibility of excised hypocotyl segmentse0
- Direction
- increasinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“constitutive expression of GFP-AtSAUR19 bypasses the normal requirement of auxin for elongation growth by increasing the mechanical extensibility of excised hypocotyl segments”
t0“Tomato”
Claim · model-written summary
PP2C.D overexpression impaired auxin-mediated hypocotyl elongation.
- Taxon
- TomatoSolanum lycopersicumt0
- Treatment
- overexpressing a PP2C.D phosphatasee0
- Gene
- PP2C.D phosphatasee0
- Outcome
- auxin-mediated elongatione0
- Direction
- impairede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“hypocotyl segments overexpressing a PP2C.D phosphatase are specifically impaired in auxin-mediated elongation”
t0“Tomato”
Claim · model-written summary
Time courses of auxin-induced SAUR expression and auxin-dependent elongation were closely correlated.
- Taxon
- TomatoSolanum lycopersicumt0
- Gene
- SAURe0
- Outcome
- auxin-dependent elongation growthe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The time courses of auxin-induced SAUR expression and auxin-dependent elongation growth were closely correlated”
t0“Tomato”
Claim · model-written summary
The authors inferred that SAUR induction can elicit expansion by activating PM H+-ATPases, acidification and wall loosening.
- Taxon
- TomatoSolanum lycopersicumt0
- Gene
- SAURe0
- Outcome
- auxin-mediated expansion growthe0
- Qualifier
- activating PM H+-ATPases to facilitate apoplast acidification and mechanical wall looseninge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“induction of SAUR expression is sufficient to elicit auxin-mediated expansion growth by activating PM H+-ATPases to facilitate apoplast acidification and mechanical wall loosening”
t0“Tomato”
The same questions in other papers
overexpression · growth · Solanum lycopersicum (tomato)Positive and negative results
3 papers in the same direction as this paper · 7 in the opposite direction
- negative
- no effect
- negative
7 papers more in this group
See all 11 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.