HE, Y; TANG, R; HAO, Y; STEVENS, R. D.; PEI, Z-M*; Duke University; Duke University; Duke University; Duke Medical Center; Duke University: Nitric Oxide Represses Arabidopsis Flowering

Nitric oxide (NO) plays an important role in many physiological processes in animals, such as smooth muscle relaxation, neurotransmission, and immune stimulation. It has also been implicated that NO also regulates multiple physiological and developmental processes in plants, including de-etiolation, seed germination, leaf expansion, senescence, stomatal closure, and responses to abiotic and biotic signals. In plants, the formation of NO can be attributed to NO synthase (NOS) and nitrate reductase, as well as non-enzymatic sources. Nevertheless, the molecular mechanisms by which NO acts remain largely unknown in plants. We found that NO represses the floral transition in Arabidopsis thaliana. Plants treated with NO, as well as a mutant overproducing NO (nox1), flowered late, whereas a mutant producing less NO (nos1) flowered early. NO suppressed CONSTANS and GIGANTEA gene expression and enhanced FLOWERING LOCUS C expression, which indicates that NO regulates the photoperiod and autonomous floral pathways. Because NO is induced by environmental stimuli and constitutively produced, it may integrate both external and internal cues into the floral decision.