Artificial targeting of a nucleus-encoded RNA-binding protein AtRZ1a to chloroplasts affects flowering and ABA response of Arabidopsis thaliana

Abstract

Despite the fact that many nucleus-encoded RNA-binding proteins (RBPs) are targeted to chloroplasts and play essential roles in RNA metabolism in chloroplasts, the question of whether artificial targeting of a nucleus-encoded RBP to chloroplasts affects chloroplast function and plant growth has never been addressed. In this study, a nuclear zinc finger-containing Arabidopsis RBP, designated AtRZ1a, which was previously shown to play a role in stress response, was artificially targeted to chloroplasts, and the growth and stress response of the transgenic plants were evaluated. Confocal analysis of the cellular localization of the cTP_AtRZ1a protein containing the N-terminal chloroplast transit peptide (cTP) from rubisco small subunit revealed that the cTP_AtRZ1a fusion protein is successfully targeted to chloroplasts. When grown under normal conditions, flowering of the transgenic plants was delayed, and the FLC expression was significantly upregulated in the transgenic plants. Artificial targeting of AtRZ1a to chloroplasts severely inhibited seedling growth of the plants in the presence of ABA by upregulating expression of ABA signaling-related genes ABI3 and ABI4. Taken together, these results suggest that artificial targeting of a nucleus-encoded AtRZ1a to chloroplasts affects the growth and development of Arabidopsis under normal or ABA treated conditions.