Integration of NO and H2S signaling in higher plants.

Nitric oxide (NO) and hydrogen sulfide (H2S) have gained significant importance in plant biochemistry and physiology due to their versatile signaling roles. These two gasotransmitters can be regarded as "twin molecules," as they participate in nearly all physiological processes and in responses to a wide range of environmental stresses. Each molecule belongs to a broader family of reactive nitrogen and sulfur species that can interact with one another, adding complexity to their regulatory functions at both the gene and protein levels. They also interact with other regulatory components, including reactive oxygen species, transcription factors, and phytohormones. This review aims to provide a comprehensive and up-to-date overview of these fascinating molecules, which continue to reveal new and unexpected functions. We propose that NO and H2S operate through a dual "butterfly" signaling mechanism, exerting either promotive or inhibitory effects, depending on the physiological context.