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Roles of nitrate, nitrite and ammonium ion in phytochrome regulation of nitrate reductase gene expression in maize
Author(s) -
Raghuram Nandula,
Sopory Sudhir K.
Publication year - 1999
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/15216549900201253
Subject(s) - nitrate reductase , nitrate , nitrite reductase , protein kinase c , ammonium , nitrite , biochemistry , chemistry , phytochrome , gene expression , stimulation , etiolation , second messenger system , signal transduction , biology , enzyme , gene , botany , endocrinology , red light , organic chemistry
The influence of nitrate and its metabolites on the nitrate reductase (NR) gene expression and its relationship with phytochrome (Pfr) regulation of NR in etiolated maize leaves is examined. Nitrate induction and Pfr stimulation are brought about by independent signalling phenomena. Phorbol myristate acetate (PMA), a stimulator of protein kinase C (PKC), mimicked the effect of red light but could not replace the nitrate requirement for the induction of NR transcript accumulation. This suggests that while PKC‐type enzymes may be involved in mediating the Pfr signal, nitrate may follow an independent signalling mechanism. Experiments with 5‐hydroxytryptamine (5HT) and lithium ions (Li+), which are known to modulate phosphoinositide (PI) turnover, indicated that in addition to generating Pfr‐induced second messengers for PKC activation, PI cycle may also generate other signals which mediate nitrate induction of NR gene expression in the dark. The products of nitrate reduction ie, nitrite and ammonium ion had inhibitory and stimulatory effects respectively, on NR transcript accumulation. They work mainly at the level of nitrate induction.