Exploring early signaling events under phosphorus restriction in soybean plants

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

Rosario

Congreso; XXXIV Reunión de la Sociedad Argentina de Fisiología Vegetal (SAB); 2023

Sociedad Argentina de Fisiología Vegetal

It has been described that nitric oxide (NO) participates in some aspects of plant mineral nutrition influencing mechanisms underlying nutrient acquisition and utilization. In order to explore NO metabolism/signaling under P restriction in soybean plants, we evaluated changes in endogenous NO levels in the first hours of P restriction, focusing on possible pathways involved in its generation (such as nitrate reductase, NR; and nitric oxide synthase like, NOSlike). Soybean seedlings (Glycine max cv. Williams 82) were grown for 7 days under controlled conditions (28°C, 200 μmol m−2 s-1 of PAR, and 16-h photoperiod) in nutrient solution. Then, plants were separated into groups receiving the following treatments for four days: P deficiency (nutrient solution without phosphate addition, -P), P deficiency plus 100 μM sodium tungstate (an inhibitor of NR activity) or 100 μM L-NAME (a known inhibitor of mammalian NOS), and full nutrient solution (500 µM phosphate, +P) as control. NO levels were evaluated employing the DAF-FM-DA probe and fluorescence microscopy, being an increase in NO levels observed in -P leaves, but not in roots. The treatment of plants with L-NAME did not affect NO levels in leaves, while the inhibition of NR activity abolished DAF-FM fluorescence. In addition, hormone levels such as indole acetic acid (IAA), gibberellic acid (GA) and abscisic acid (ABA) were evaluated. Four days after P restriction no significant differences were observed in IAA levels neither in leaves nor in roots of P-starved plants, as compared to control; however, the content of GA3 significantly decreased in roots of -P plants. ABA levels were increased in -P roots as compared to control values. Interestingly, the treatment of -P plants with sodium tungstate did not restored ABA and GA levels to control values. Overall, the data presented here suggest a possible role for ABA, GA, and NO in signaling events during the first hours of P deprivation in soybean plants.