NO and ROS promote hypocotyl cell growth under shade in plants

IGLESIAS MJ; ROJAS, CECILIA COSTIGLIOLO; BIANCHIMMANO LUCIANA; CASAL JJ

Congreso; 9TH PLANT NITRIC OXIDE INTERNATIONAL MEETING (PNO9); 2024

In the last 25 years since its discovery as a molecular signal in plants, nitric oxide (NO) has been associated to several plants responses. However, its role in synergism with reactive oxygen species (ROS) in the regulation of cell growth under environmental changes is not completely deciphered. Shade promotes the growth of the stem (hypocotyl) to facilitate plant access to light in crowded environments. Our results show that auxin produced in response to shade triggers the accumulation of ROS and NO in the hypocotyl, causing a more oxidative environment, which enhanced the promotion of polar cell growth in this organ. Under shade, NO bioactivity is efficiently transferred and stored within the cell through its co-valent attachment to specific reactive cysteine thiols of proteins, increasing S-nitrosylation. We proposed that a major role for the rapid, transcient and largely parallel increment of ROS and NO in the hypocotyl is to engage a specific set of NO-responsive proteins. We demonstrate the S-nitrosylation of central regulators of light signaling. Impairing these modifications reduced protein stability, its ability to interact with some partners and its biological activity under shade. Disabling this regulation also generated transversal asymmetries in hypocotyl growth, indicating poor coordination among different cells, which resulted in random bending and predictably low ability to compete with neighbours.