Nitrate-regulated seed germination

Abstract

Nitrate promotes seed germination in many plant species.　Its effect can be seen at low concentrations （< 1 mM） and even in the nitrate reductase deficient mutant, suggesting that nitrate itself, not assimilates, acts as a signal to promote seed germination.　Arabidopsis molecular genetics research have revealed that nitrate-induced expression of CYP707A2, encoding an abscisic acid （ABA） catabolism enzyme, play an important role in this process.　This regulation involves NIN-LIKE PROTEIN 8 （NLP8） transcription factor.　Nitrate activates NLP8, which allows directly binding the Nitrate Responsive Element （NRE） in the CYP707A2 promoter.　The induction of CYP707A2 leads to the decrease in seed ABA contents, which in turn promotes seed germination.　Understanding the function of nitrate in plants will be useful to create crops with low nitrogen use.