Abstract
Maize (Zea mays) stem gravitropism involves differential elongation of cells within a highly specialized region, the stem internodal pulvinus. In the present study, we investigated factors that control gravitropic responses in this system. In the graviresponding pulvinus, hexose sugars (D-Glc and D-Fru) accumulated asymmetrically across the pulvinus. This correlated well with an asymmetric increase in acid invertase activity across the pulvinus. Northern analyses revealed asymmetric induction of one maize acid invertase gene, Ivr2, consistent with transcriptional regulation by gravistimulation. Several lines of evidence indicated that auxin redistribution, as a result of polar auxin transport, is necessary for gravity-stimulated Ivr2 transcript accumulation and differential cell elongation across the maize pulvinus. First, the auxin transport inhibitor, N-1-naphthylphthalamic acid, inhibited gravistimulated curvature and Ivr2 transcript accumulation. Second, a transient gradient of free indole-3-acetic acid (IAA) across the pulvinus was apparent shortly after initiation of gravistimulation. This temporarily free IAA gradient appears to be important for differential cell elongation and Ivr2 transcript accumulation. This is based on the observation that N-1-naphthylphthalamic acid will not inhibit gravitropic responses when applied to pulvinus tissue after the free IAA gradient peak has occurred. Third, IAA alone can stimulate Ivr2 transcript accumulation in non-gravistimulated pulvini. The gravity- and IAA-stimulated increase in Ivr2 transcripts was sensitive to the protein synthesis inhibitor, cycloheximide. Based on these results, a two-phase model describing possible relationships between gravitropic curvature, IAA redistribution, and Ivr2 expression is presented.
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Claims 9
Claim · model-written summary
Hexose sugars accumulated asymmetrically in graviresponding maize pulvini.
- Organ / stage
- pulvinuse0
- Outcome
- hexose sugars (D-Glc and D-Fru)e0
- Direction
- accumulated asymmetricallye0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the graviresponding pulvinus, hexose sugars (D-Glc and D-Fru) accumulated asymmetrically across the pulvinus.”
t0“Maize Pulvinal Cells”
Claim · model-written summary
Acid invertase activity increased asymmetrically across the pulvinus.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This correlated well with an asymmetric increase in acid invertase activity across the pulvinus.”
t0“Maize Pulvinal Cells”
Claim · model-written summary
Gravistimulation asymmetrically induced Ivr2 expression.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Northern analyses revealed asymmetric induction of one maize acid invertase gene, Ivr2, consistent with transcriptional regulation by gravistimulation.”
Claim · model-written summary
Auxin transport inhibition blocked gravistimulated curvature.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the auxin transport inhibitor, N-1-naphthylphthalamic acid, inhibited gravistimulated curvature and Ivr2 transcript accumulation.”
t0“Maize Pulvinal Cells”
Claim · model-written summary
Auxin transport inhibition blocked Ivr2 transcript accumulation.
- Treatment
- N-1-naphthylphthalamic acide0
- Gene
- Ivr2e0
- Outcome
- Ivr2 transcript accumulatione0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the auxin transport inhibitor, N-1-naphthylphthalamic acid, inhibited gravistimulated curvature and Ivr2 transcript accumulation.”
t0“Maize Pulvinal Cells”
Claim · model-written summary
A transient free IAA gradient appeared after gravistimulation began.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a transient gradient of free indole-3-acetic acid (IAA) across the pulvinus was apparent shortly after initiation of gravistimulation.”
t0“Maize Pulvinal Cells”
Claim · model-written summary
Applying the inhibitor after the IAA gradient peak did not inhibit gravitropic responses.
- Treatment
- N-1-naphthylphthalamic acide0
- Outcome
- gravitropic responsese0
- Direction
- will not inhibite0
- Qualifier
- after the free IAA gradient peak has occurrede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N-1-naphthylphthalamic acid will not inhibit gravitropic responses when applied to pulvinus tissue after the free IAA gradient peak has occurred.”
t0“Maize Pulvinal Cells”
Claim · model-written summary
IAA stimulated Ivr2 transcript accumulation without gravistimulation.
- Treatment
- IAAe0
- Gene
- Ivr2e0
- Outcome
- Ivr2 transcript accumulatione0
- Direction
- stimulatee0
- Comparator
- non-gravistimulated pulvinie0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“IAA alone can stimulate Ivr2 transcript accumulation in non-gravistimulated pulvini.”
t0“Maize Pulvinal Cells”
Claim · model-written summary
Cycloheximide inhibited gravity- and IAA-stimulated Ivr2 transcript increases.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The gravity- and IAA-stimulated increase in Ivr2 transcripts was sensitive to the protein synthesis inhibitor, cycloheximide.”
t0“Maize Pulvinal Cells”
The same questions in other papers
naptalam · molecular: expression · Zea mays (maize)Positive and negative results
1 in the opposite direction
- positive
indole-3-acetic acid · molecular: expression · Zea mays (maize)Positive and negative results
2 papers in the same direction as this paper · 1 in the opposite direction
- no effect
- positive
- positive
cycloheximide · molecular: expression · Zea mays (maize)Positive and negative results
3 papers in the same direction as this paper · 1 in the opposite direction
- positive
- no effect
- negative
1 paper more in this group
See all 5 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.