Carbon Monoxide: A Ubiquitous Gaseous Signaling Molecule in Plants

Abstract

Carbon monoxide (CO) is an important gaseous signaling molecule, second only in importance to nitric oxide (NO). It has a diverse array of physiological functions in plants. In response to environmental stress and under specific developmental conditions, endogenous CO production is induced which was observed in a number of different plant species and organs. Until now, the use of CO fumigation, its aqueous solution, or the artificial CO donor hematin and hemin, combined with the genetic approach, illustrated that CO performs a crucial role in plant growth and development, beginning with germination and ending in the senescence of organs. Unfortunately, in spite of many important discoveries of the role of CO in regulating plant physiology, it is still difficult to present a relatively comprehensive understanding of CO functions and signaling in plants. In this chapter, we summarize the evidence, showing that CO performs an essential role in regulating plant responses against abiotic stress and in plant developmental process. The interaction among CO, other gaseous signaling molecules, and phytohormones was illustrated. These results support the idea that similar to the biological functional roles of NO in plants, CO might be another "do-it-all" molecule during the whole lifespan of the plant.