Abstract
As a second messenger, calcium is involved in auxin signaling, and previous studies demonstrated that Arabidopsis CAX1 (Ca 2+ /H + exchanger) is involved in the auxin transduction pathway. This study was performed to investigate the possible role of auxin-binding proteins ABP1 and ABP4 in Ca 2+ /auxin-regulated growth in maize (Zea mays L.). We identified and cloned two AtCAX1 homologs in maize, ZCAX2 and ZCAX3. Using maize loss-of-function abp1 and abp4 mutants, the role of ABPs in Ca 2+ -dependent growth and in the Ca 2+ /auxin-regulated expression of the CAX genes was investigated in etiolated maize seedlings. Exogenous Ca 2+ enhanced mesocotyl but not coleoptile growth in WT, abp1, abp4, and abp1/abp4 mutants, but the maximum stimulation was in abp4. As well, in the abp4 mutant, maximum accumulation of Ca 2+ was observed when seedlings were exposed to exogenous Ca 2+ . In the mesocotyl of abp4 and double mutants, the expression of ZCAX3 was significantly reduced in the absence of exogenous Ca 2+ , whereas exogenous Ca 2+ significantly up-regulated its expression in both mutants. This effect of Ca 2+ was not observed in the coleoptile. In the absence of NAA, knockout of ABP4 led to significant drop of ZCAX3 expression in the mesocotyl, and exogenous auxin significantly inhibited expression of the ZCAX3 in WT, but not in abp mutants. This effect of auxin was not observed in the coleoptile. Our results indicate that in the absence of NAA, functional ABP4 is required for ZCAX3 expression and that ABP4 mediates the inhibitory effect of NAA on ZCAX3 expression. We provided evidence for a cross talk between ABP4, exogenous auxin, Ca 2+ , and ZCAX3 during growth of etiolated maize mesocotyl.
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Claims 15
Claim · model-written summary
Two AtCAX1 homologs, ZCAX2 and ZCAX3, were identified and cloned in maize.
Zea maysNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We identified and cloned two AtCAX1 homologs in maize, ZCAX2 and ZCAX3.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Exogenous calcium enhanced mesocotyl growth in WT, abp1, abp4, and double mutants.
- Material
- WT, abp1, abp4, and abp1/abp4 mutantse0
- Treatment
- Exogenous Ca 2+e0
- Outcome
- mesocotyle0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous Ca 2+ enhanced mesocotyl but not coleoptile growth in WT, abp1, abp4, and abp1/abp4 mutants, but the maximum stimulation was in abp4.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Exogenous calcium did not enhance coleoptile growth in the four maize genotypes.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous Ca 2+ enhanced mesocotyl but not coleoptile growth in WT, abp1, abp4, and abp1/abp4 mutants, but the maximum stimulation was in abp4.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
The abp4 mutant showed the maximum calcium stimulation of mesocotyl growth.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the maximum stimulation was in abp4.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
The abp4 mutant showed maximum calcium accumulation after exogenous calcium exposure.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the abp4 mutant, maximum accumulation of Ca 2+ was observed when seedlings were exposed to exogenous Ca 2+”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Without exogenous calcium, ZCAX3 expression was significantly reduced in abp4 mesocotyls.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the mesocotyl of abp4 and double mutants, the expression of ZCAX3 was significantly reduced in the absence of exogenous Ca 2+”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Without exogenous calcium, ZCAX3 expression was significantly reduced in double-mutant mesocotyls.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the mesocotyl of abp4 and double mutants, the expression of ZCAX3 was significantly reduced in the absence of exogenous Ca 2+”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Exogenous calcium significantly increased ZCAX3 expression in abp4 mesocotyls.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exogenous Ca 2+ significantly up-regulated its expression in both mutants.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Exogenous calcium significantly increased ZCAX3 expression in double-mutant mesocotyls.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exogenous Ca 2+ significantly up-regulated its expression in both mutants.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Calcium did not produce this ZCAX3 expression effect in coleoptiles.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This effect of Ca 2+ was not observed in the coleoptile.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
ABP4 knockout significantly reduced ZCAX3 mesocotyl expression without NAA.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the absence of NAA, knockout of ABP4 led to significant drop of ZCAX3 expression in the mesocotyl”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Exogenous auxin significantly inhibited ZCAX3 expression in WT maize.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exogenous auxin significantly inhibited expression of the ZCAX3 in WT, but not in abp mutants.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Exogenous auxin did not inhibit ZCAX3 expression in abp mutants.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exogenous auxin significantly inhibited expression of the ZCAX3 in WT, but not in abp mutants.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Auxin did not produce the ZCAX3 expression effect in coleoptiles.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This effect of auxin was not observed in the coleoptile.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
Claim · model-written summary
Functional ABP4 is required for ZCAX3 expression without NAA and mediates NAA inhibition.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Our results indicate that in the absence of NAA, functional ABP4 is required for ZCAX3 expression and that ABP4 mediates the inhibitory effect of NAA on ZCAX3 expression.”
t0“maize (Zea mays)”
t1“abp4 and double mutants”
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