The role of carbon monoxide signaling in the responses of plants to abiotic stresses

Whether carbon monoxide (CO) exerts toxic or protective effect is dependent on the concentration and location of CO in animals. Similarly, it has been increasingly evident that CO also is involved in diverse physiological processes in plants, from seed germination and dormancy to stomatal closure to regulation of multiple environmental stresses. In this review, we focus on CO synthesis and the role of CO in plant responses to abiotic stresses, such as salinity, drought, cadmium and mercury. In general, abiotic stresses induce CO production in plants. CO can alleviate oxidative damage by improving the activities of antioxidative enzymes and antioxidant metabolism. In addition, cross talk between CO signaling and other signaling molecules including nitric oxide (NO) and hydrogen peroxide (H2O2) also is discussed.