NO way! Is nitric oxide level in tomato regulated by a mammalian IKK/NF-κB like signaling pathway?

Nitric oxide (NO) is an essential signaling molecule in plants. However little is known about signaling pathways regulating NO levels in plants. Recently we reported a NO overproducing mutant of tomato that had extremely short roots (shr) at seedling stage. The scavenging of NO restored root elongation in the shr mutant providing us with a convenient bioassay to analyze the signaling pathway upstream of NO production. The application of previously reported pharmacological inhibitors of ubiquitin-proteasome signaling caused a drastic reduction in NO levels and restored root elongation in the mutant. Since these pharmacological inhibitors specifically inhibit mammalian IKK/NF-κB signaling, we propose that a pathway functionally similar to IKK/NF-κB pathway regulates NO levels in tomato.