Endogenous nitric oxide influences acclimation responses to phosphorus restriction in soybean plants

LUQUET, MELISA; ANTONELLI, CRISTIAN JAVIER; GERGOFF GROZEFF, GUSTAVO ESTEBAN; BUET, AGUSTINA; GALATRO, ANDREA

Mendoza

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research (SAIB); 2022

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular

The bioavailability of phosphate (P) in soils is usually low, where its mobility is also restricted. To sustain P levels, plants have developed mechanisms to improve P acquisition from the soil solution, and P reutilization from internal sources. Nitric oxide (NO), a gaseous free radical molecule, is a critical component in plant acclimation responses to abiotic stress conditions, such as mineral nutrient disbalances. In this work, we evaluated changes in endogenous NO levels following P deprivation in soybean plants, and its influence in some typical acclimation responses. Seedlings (Glycine max cv. Williams 82) were grown for 7 days under controlled conditions (28°C/22°C day-night, 400 μmol m−2 s-1 of PAR, and 16-h photoperiod) in modified Hoagland nutrient solution (500 μM H3PO4, +P). Then, plants were separated into three groups receiving the following treatments: P deficiency (nutrient solution without H3PO4 addition, -P), P deficiency added with 100 μM sodium tungstate (an inhibitor of NR activity), and full nutrient solution (+P) as a control. Typical acclimation responses were evaluated in plants up to 96h of P restriction, where P concentration significantly decreased in roots and unifoliate leaves (64 % as compared to control plants), but neither growth nor photosynthesis was hardly affected. NO levels were evaluated employing the DAF-FM-DA probe and fluorescence microscopy. In this sense, an increase in NO levels in -P leaves was observed, and the treatment with sodium tungstate reduced this increase in -P plants. Acid phosphatase (AP) activity, RNase activity, and organic acids (malic and citric acids) content were evaluated at 96h of treatment. RNase and AP activities were significantly increased in -P roots (55% and 80% respectively) as compared to control, and the same trend was observed in leaves. Citric acid and malic acid levels, evaluated by HPLC, also increased in -P roots. The treatment of plants with sodium tungstate reduced the magnitude of these acclimation responses to control levels. Inaddition, changes in hormone levels (such as ABA and GA) were induced under P restriction. Overall, the data here presented might indicate the involvement of NO in signaling pathways related to acclimation responses during the first hours of P deprivation and the involvement of NR as NO source.