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

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

Congreso; Reunión anual de la Sociedad de investigación en Bioquímica y Biología molecular (SAIB), Edición LVIII; 2022

SAIB

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. In addition, 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