Functional relationship heavy metal P-type ATPases (OsHMA 2 and OsHMA3) of rice (Oryza sativa) using RNAi

Abstract

Oryza sativa heavy metal P-type ATPase 3 (OsHMA3) plays a major role in the hyperaccumulation of cadmium (Cd) by the rice cultivars ‘Cho-Ko-Koku (CKK)’ and ‘Anjana Dhan.’ On the other hand, mutants that accumulate Cd in the shoots at a very low level have suggested the function of several genes such as OsHMA2 (which is neccesary to load Cd into xylem) or O. sativa natural resistance-associated macrophage protein 5 (OsNRAMP5, which regulates the uptake of Cd from soil into the roots). Although many studies have examined metal transporters, few have investigated the function of combination of multiple gene in plant. Herein, first, we used an RNA interference (RNAi) method to down regulate OsHMA3 and recovered plants in which the expression of OsHMA3 was strongly suppressed. Second, crossing of OsHMA3 RNAi plants with oshma2 mutants revealed a functional relationship between OsHMA3 and OsHMA2 in plant. We concluded that a complete loss of function of OsHMA2 is crucial to minimize Cd translocation from the roots to the shoots. The current findings also implied that the activity of OsHMA2 can be accelerated in plant in the roots without the C-terminal region of the protein.