Nitric oxide participates in plant flowering repression by ascorbate

Abstract

In Oncidium, redox homeostasis involved in flowering is mainly due to ascorbic acid (AsA). Here, we discovered that Oncidium floral repression is caused by an increase in AsA-mediated NO levels, which is directed by the enzymatic activities of nitrate reductase (NaR) and nitrite reducatase (NiR). Through Solexa transcriptomic analysis of two libraries, ‘pseudobulb with inflorescent bud’ (PIB) and ‘pseudobulb with axillary bud’ (PAB), we identified differentially expressed genes related to NO metabolism. Subsequently, we showed a significant reduction of NaR enzymatic activities and NO levels during bolting and blooming stage, suggesting that NO controlled the phase transition and flowering process. Applying AsA to Oncidium PLB (protocorm-like bodies) significantly elevated the NO content and enzyme activities. Application of sodium nitroprusside (-NO donor) on Arabidopsis vtc1 mutant caused late flowering and expression level of flowering-associated genes (CO, FT and LFY) were reduced, suggesting NO signaling is vital for flowering repression. Conversely, the flowering time of noa1, an Arabidopsis NO-deficient mutant, was not altered after treatment with L-galacturonate, a precursor of AsA, suggesting AsA is required for NO-biosynthesis involved in the NO-mediated flowering-repression pathway. Altogether, Oncidium bolting is tightly regulated by AsA-mediated NO level and downregulation of transcriptional levels of NO metabolism genes.

Biosynthesis and Cellular Functions of Tartaric Acid in Grapevines

“…As reviewed by Foyer et al (2020) , Asc can regulate flowering time via the NO-mediated flowering repression pathway ( Kumar et al, 2016 ), such that application of Asc or L-galactonolactone delays flowering, while knockout mutants of various Vtc genes in A. thaliana (i.e., less Asc) flower earlier ( Kotchoni et al, 2009 ). Genetic modification of AO led to altered expression and diurnal regulation of catalase genes and photorespiration-related genes in tobacco, as well as altered DHAR and APX activities, MAPK activity and growth response to auxins ( Pignocchi et al, 2006 ).…”

Plant Nitric Oxide Signaling under Drought Stress

“…Other RNSs include peroxynitrite (ONOO−), S-nitrosoglutathione (GSNO), and S-nitrosothiols (SNOs). NO and RNS are involved in various developmental and physiological processes, such as seed germination and dormancy [ 31 ], shoot and root growth [ 32 ], flowering [ 33 ], fruit ripening [ 34 ], yield [ 35 ], stomatal closure [ 36 ], formation of guard cells [ 37 ], senescence [ 38 ], photosynthesis regulation [ 39 ], mitochondria functionality [ 30 ], gravitropism [ 40 ] and pollen tube growth [ 41 ]. The way by which NO and RNS exert their function is still largely unknown.…”

Cyclic nucleotide-gated ion channel 6 mediates thermotolerance in Arabidopsis seedlings by regulating nitric oxide production via cytosolic calcium ions

“…Nitric oxide (NO) is a key signaling molecule that participates in a number of processes throughout the life cycle of plants, including seed germination and dormancy, plant growth and development, flowering, and the interactions of plants with biotic or abiotic stresses [2, 3]. Arginine-denpendent NO synthase (NOS) and nitrite-dependent nitrate reductase (NR) are two important enzymes for NO production in plants.…”