Cadmium (Cd) is a toxic element to plant, animal and human. With increased Cd concentration in agricultural soils due to human activities, such as application of phosphate fertilizer, sewage sludge, wastewater and pesticide, Cd pollution has become a serious problem for environment. Cd is rapidly taken up by roots and enters the food chain, resulting toxic for plants, animals and human beings. Thus decreasing the amount of Cd absorption and controlling the Cd translocation from root to edible part of plant is the hot topics in this research area.
Scientists in Dr. Hongqing Ling’s group from the Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences found out that FIT, AtbHLH38 and AtbHLH39, three basic helix-loop-helix transcription factors involved in iron homeostasis in plants, also play important roles in Cd tolerance. The gene expression analysis showed that the expression of FIT, AtbHLH38 and AtbHLH39 was up-regulated in the roots of plants treated with Cd. The plants double-overexpressing FIT/AtbHLH38 and FIT/AtbHLH39 exhibited more tolerance to Cd exposure than wild type. Further analysis showed that Co-overexpression of FIT with AtbHLH38 or AtbHLH39 in Arabidopsis constitutively activated the expression of HMA3, MTP3, IREG2, IRT2, NAS1 and NAS2 directly or indirectly, resulting in Cd sequestration in roots to maintain a relative low cellular Cd concentration in shoot, and enhancement of iron transportation from root to shoot to keep the iron homeostasis in shoot. These two factors contribute plants double-overexpressing FIT with AtbHLH38 or AtbHLH39 more tolerance to Cd under the culture condition with Cd. The results provide a new insight to understand the molecular mechanisms of Cd tolerance and a potential way to control Cd accumulation in plants by genetic improvement.
This work with Dr. Huilan Wu as the first author has been online published on Plant Physiology (DOI: 10.1104/pp.111.190983.). This research was supported by grants from National Natural Science Foundation of China, Ministry of Science and Technology, International Cooperation Project HarvestPlus.
AUTHOR CONTACT:
Hongqing Ling, Ph.D.
Institute of Genetics and Developmetnal Biology, Chinese Academy of Sciences, Beijing, China.
