Induction of endogenous mechanisms contributes to engineering metal accumulation and tolerance

Danuta Maria Antosiewicz

Induction of endogenous mechanisms contributes to engineering metal accumulation and tolerance

Danuta Maria Antosiewicz

University of Warsaw, Poland

: J Plant Physiol Pathol

Abstract

Metal-homeostasis genes are expressed in plants to modify metal uptake, accumulation and tolerance for phytoremediation and biofortification purposes. However, the phenotype generated in transgenic plants has often been far from expected. In addition, the expression of a transgene failed to yield one set pattern of metal/s accumulation/distribution in plant organs at varying medium composition. Our study performed on wild-type and transgenic tobacco and tomato expressing various Zn and Cd transporters (including HMA4 from Arabidopsis thaliana and Arabidopsis halleri) indicates that expression of the introduced gene deregulates a metal/s balance in a host plant and changes metal status at a cellular/tissue/organ level. To counteract, endogenous metal homeostasis mechanisms are activated which contribute to generation of characteristic features of transgenic plants. To understand underlying molecular mechanisms, comparative analysis was performed at the organ level with the use of microarray and Suppression Subtractive Hybridization (SSH), and at the tissue level applying Laser Capture Microdissection (LCM) followed by microarray and Real Time-qPCR analysis. These studies were accompanied by physiological and biochemical analysis. Key genes involved in the regulation of the phenomenon of Zn/Cd supply-dependent of Zn/Cd root/shoot partitioning in wild-type plants, and in modifications resulting from expression of HMA4 have been identified. Modification of the expression level of endogenous metal-homeostasis genes in transgenic plants were highly tissuespecific (in examined roots and leaves) and involved ethylene pathway and ethylene-dependent metal transport genes. Thus, secondary effects induced by a transgene expression are an integral part of the mechanism involved in engineering of metalrelated desired traits in plants.