Cadmium (Cd) and arsenic (As) contamination of soil and water causing toxicity/stress to food plants is an important constraint to crop productivity and quality. A plant exposed to toxic metals triggers a wide range of physiological and biochemical alterations and develops a series of strategies that allow to cope with the negative consequences of element toxicity. Roots are the first organs that encounter toxic metals. Thus roots must implement the strategies needed to reduce the negative effects of the toxic elements and possibly limit their transfer to edible organs.
Oryza sativa L. is one of the most cultivated food species, but it easy absorbs Cd and As. The latter causes dangerous effects on root development and plant growth and productivity. The correct distribution of auxin, due to a hormone polar transport and a local synthesis in the root meristem, is required for the genesis and maintenance of a functioning root system. The alterations in the synthesis/transport of auxin compromise root functionality. Cd and As accumulate in the root meristem and exert a negative action on the hormone homeostasis. Nitric oxide (NO) is involved in plant stress responses. It interacts with auxins during abiotic stress involving peroxisome activity. The role of peroxisomes in Cd/As induced responses, and, in particular, in the control of auxin metabolism in rice root, is poorly known. The thiols, particularly phytochelatins and their precursor GSH, bind As and Cd, resulting in toxicity alleviation. Furthermore, it is also known that metal-exposed plants show significant increases in the synthesis of secondary metabolites with antioxidant activity to protect the cells from the oxidative damages. The aims of the Proposal are to investigate the auxin-NO interaction during root formation in rice exposed to Cd/As, to analyze the variation of the thiol levels in the root and characterize the secondary metabolites involved, in relation to auxin and NO metabolism modifications.
