Light suppression of nitrate reductase activity in seedling and young plant tissues

Authors

Mark A. Schoenbeck, University of Nebraska at OmahaFollow
Bikash Shrestha, University of Nebraska at OmahaFollow
Melanie F. McCormick, University of Nebraska at OmahaFollow
Timothy D. Kellner, University of Nebraska at OmahaFollow
Claudia M. Rauter, University of Nebraska at OmahaFollow

Date of this Version

10-23-2015

Document Type

Article

Citation

Transactions of the Nebraska Academy of Sciences 35 (2015), pp. 41–52

Comments

Copyright (c) 2015 Mark A. Schoenbeck, Bikash Shrestha, Melanie F. McCormick, Timothy D. Kellner, and Claudia M. Rauter.

Abstract

Light is often reported to enhance plant nitrate reductase (NR) activity; we have identified a context in which light strongly suppresses NR activity. In vitro NR activity measurements of laboratory-grown seedlings showed strong suppression of nitrate-induced NR activity in cotyledon, hypocotyl, and root tissues of Ipomoea hederacea (L.) Jacquin; robust NR activity accumulated in nitrate-induced tissues in the dark, but was absent or significantly reduced in tissues exposed to light during the incubation. The suppressive mechanism appears to act at a point after nitrate perception; tissues pre-incubated with nitrate in the light were potentiated and developed NR activity more rapidly than nitrate-induced tissues not so pre-exposed. Suppression was affected by moderate to low light levels under full-spectrum light sources and by single-wavelength red, green, and blue sources. The suppression phenomenon persisted in early (first through fourth) leaves of glasshouse plants grown in soil, and in artificially rejuvenated cotyledons. Collectively these observations suggest a link between light perception and NR regulation that remains to be fully characterized.