Circadian Patterns of the Major Nitrogen Metabolism–Related Enzymes and Metabolites in Creeping Bentgrass and the Influence of Cytokinin and Nitrate
- Kehua Wang *ac,
- Sakiko Okumotob,
- Xunzhong Zhanga and
- Erik Ervina
- a Dep. of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State Univ., Blacksburg, VA, 24061
c Division of Plant Sciences, Univ. of Missouri, Columbia, MO, 65211
b Dep. of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State Univ., Blacksburg, VA, 24061
Creeping bentgrass (Agrostis stolonifera L.) is a major low-cut turfgrass species worldwide. Information is limited on the diurnal variation in its N metabolism, particularly the impacts of cytokinin (CK) and nitrate (NO3–). To gain insight into the diurnal fluctuation of N metabolism and the effects of CK and nitrate, the transcript abundance of the major N metabolism enzymes in shoots, including nitrate reductase (NR), nitrite reductase, chloroplastic glutamine synthetase (GS2), ferredoxin-dependent glutamate synthase (Fd-GOGAT), and glutamate dehydrogenase, were studied during the day/night cycle (14/10 h). All measured parameters exhibited clear diurnal changes with some differences among treatments (control, CK at 50 μM, and nitrate at 7.5 kg N ha−1), except GS2 expression and total protein. Both NR expression and nitrate content showed a peak at 0430 h (8.5 h in dark). Nitrate nutrition increased diurnal change of nitrate content, showing an over two-fold diurnal difference compared to 63 and 81% differences for the control and CK treatment, respectively. Simultaneously, CK shifted the diurnal in vivo NR activity pattern. In addition, creeping bentgrass appears to be able to maintain N assimilation at night comparable to that during the day, demonstrated by either similar or even higher levels of measured parameters between certain phases of light and dark periods. This study provides further information for understanding how CK and nitrate regulate N metabolism in creeping bentgrass.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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