Abstract
Both light and NO3- are necessary for the appearance of nitrate reductase (NR) activity (NRA) in photosynthetic tissues. To define the light effect more precisely, we examined the response to light/dark transitions on NRA, NR protein (NRP), and NR mRNA in 6-d-old maize (Zea mays cv W64A x W182E) seedlings that had been grown in a light/dark regime for 5 d and then induced with 5 mM KNO3 for 24 h. The decay of NRA and NR mRNA in the shoot was immediate, but there were only minor changes in NRP during the initial 4 h in the dark. In root tissues, in contrast, there was a 4-h delay in the loss of NRA, NRP, and NR mRNA after transfer to the dark. When the seedlings were returned to light after a 2-h interval in the dark, shoot NRA reached 92% of the initial levels within 30 min of illumination. These results indicate that in the shoots (a) NR message production requires light and (b) the NRP that appears with light treatment and that is active is inactivated in the dark. The NRP can be reactivated when the light is turned on after short periods of darkness (2 h). Root tissues, on the other hand, probably respond to the supply of photosynthetically produced metabolites rather than to immediate products of the light reactions of photosynthesis.
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Claims 8
Claim · model-written summary
Shoot nitrate reductase activity and mRNA decayed immediately after dark transfer.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The decay of NRA and NR mRNA in the shoot was immediate, but there were only minor changes in NRP during the initial 4 h in the dark.”
t0“Zea mays”
Claim · model-written summary
Shoot nitrate reductase protein changed only slightly during the first four hours of darkness.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there were only minor changes in NRP during the initial 4 h in the dark.”
t0“Zea mays”
Claim · model-written summary
Root nitrate reductase activity, protein and mRNA loss was delayed four hours after dark transfer.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In root tissues, in contrast, there was a 4-h delay in the loss of NRA, NRP, and NR mRNA after transfer to the dark.”
t0“Zea mays”
Claim · model-written summary
Shoot NRA recovered to 92% of initial levels within 30 minutes after return to light.
- Treatment
- illuminatione0
- Outcome
- shoot NRAe0
- Direction
- reachede0
- Value
- 92%e0
- Qualifier
- within 30 mine0
- Comparator
- initial levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“shoot NRA reached 92% of the initial levels within 30 min of illumination.”
t0“Zea mays”
Claim · model-written summary
Authors infer that shoot NR message production requires light.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NR message production requires light”
t0“Zea mays”
Claim · model-written summary
Authors infer that darkness inactivates the light-induced active NR protein.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the NRP that appears with light treatment and that is active is inactivated in the dark.”
t0“Zea mays”
Claim · model-written summary
NR protein can reactivate after light follows a two-hour dark interval.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The NRP can be reactivated when the light is turned on after short periods of darkness (2 h).”
t0“Zea mays”
Claim · model-written summary
Root response probably follows photosynthetically produced metabolites rather than immediate light-reaction products.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Root tissues, on the other hand, probably respond to the supply of photosynthetically produced metabolites rather than to immediate products of the light reactions of photosynthesis.”
t0“Zea mays”
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