Abstract
Changes in cytoplasmic Ca2+ levels are involved in the regulation of several plant genes. However, to our knowledge, no regions of genes or specific cis elements have been shown to be involved in the regulation of plant gene expression by cytosolic Ca2+ signaling. The maize (Zea mays) gene cab-m1, which encodes a light-harvesting chlorophyll a/b-binding apoprotein, is positively photoregulated in mesophyll cells (MC) but not in bundle-sheath cells (BSC). This gene is highly preferentially expressed in maize MC versus BSC. In situ transient expression assays have revealed that exposure of tissues to ethyleneglycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA), which chelates Ca2+, blocks the photostimulation of cab-m1 full promoter (-1026 to + 14) activity in MC of leaf segments of dark-grown maize seedlings. EGTA has no effect on expression in BSC. These results suggest that light-induced elevation of the cytosolic Ca2+ concentration in MC is required for the enhancement of cab-m1 expression in MC. Deletion of the sequence from -1026 to -360 completely abolished Ca2+ responsiveness of cab-m1 expression in MC. On the other hand, a 54-bp fragment in the 5' flanking region (-953 to -899 relative to the translation start site) conferred Ca2+ responsiveness on a -359 core promoter: reporter gene, suggesting that Ca2+ signaling is mediated via specific sequences in this short fragment. Furthermore, possible involvement of Ca(2+)-calmodulin in the signal transduction chain for regulating cab-m1 expression was suggested by the results of inhibitor experiments.
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Claims 7
Claim · model-written summary
Maize cab-m1 is photoregulated in mesophyll but not bundle-sheath cells.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The maize (Zea mays) gene cab-m1, which encodes a light-harvesting chlorophyll a/b-binding apoprotein, is positively photoregulated in mesophyll cells (MC) but not in bundle-sheath cells (BSC).”
Claim · model-written summary
cab-m1 expression is highly preferential in maize mesophyll versus bundle-sheath cells.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This gene is highly preferentially expressed in maize MC versus BSC.”
t0“Maize cab-m1”
Claim · model-written summary
EGTA blocked photostimulation of cab-m1 full-promoter activity in maize mesophyll cells.
- Organ / stage
- MC of leaf segments of dark-grown maize seedlingse0
- Treatment
- ethyleneglycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA)e0
- Outcome
- photostimulation of cab-m1 full promoter (-1026 to + 14) activitye0
- Direction
- blockse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exposure of tissues to ethyleneglycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA), which chelates Ca2+, blocks the photostimulation of cab-m1 full promoter (-1026 to + 14) activity in MC of leaf segments of dark-grown maize seedlings.”
Claim · model-written summary
EGTA had no effect on maize bundle-sheath expression.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“EGTA has no effect on expression in BSC.”
t0“Maize”
Claim · model-written summary
Deleting the -1026 to -360 sequence abolished calcium responsiveness of cab-m1 in maize mesophyll cells.
- Treatment
- Deletion of the sequence from -1026 to -360e0
- Gene
- cab-m1e0
- Outcome
- Ca2+ responsiveness of cab-m1 expression in MCe0
- Direction
- completely abolishede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Deletion of the sequence from -1026 to -360 completely abolished Ca2+ responsiveness of cab-m1 expression in MC.”
t0“Maize”
Claim · model-written summary
A 54-bp flanking fragment conferred calcium responsiveness on a maize cab-m1 core promoter reporter.
- Treatment
- a 54-bp fragment in the 5' flanking region (-953 to -899 relative to the translation start site)e0
- Gene
- cab-m1t0
- Outcome
- Ca2+ responsivenesse0
- Direction
- conferrede0
- Comparator
- -359 core promotere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a 54-bp fragment in the 5' flanking region (-953 to -899 relative to the translation start site) conferred Ca2+ responsiveness on a -359 core promoter: reporter gene”
t0“Maize cab-m1”
Claim · model-written summary
Inhibitor experiments suggested possible calcium-calmodulin involvement in maize cab-m1 regulation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“possible involvement of Ca(2+)-calmodulin in the signal transduction chain for regulating cab-m1 expression was suggested by the results of inhibitor experiments.”
t0“Maize”
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