OsCpn60β1 is Essential for Chloroplast Development in Rice (Oryza sativa L.)

Abstract

The chaperonin 60 (Cpn60) protein is of great importance to plants due to its involvement in modulating the folding of numerous chloroplast protein polypeptides. In chloroplasts, Cpn60 is differentiated into two subunit types-Cpn60α and Cpn60β and the rice genome encodes three α and three β plastid chaperonin subunits. However, the functions of Cpn60 family members in rice were poorly understood. In order to investigate the molecular mechanism of <i>OsCpn60β1</i>, we attempted to disrupt the <i>OsCpn60β1</i> gene by CRISPR/Cas9-mediated targeted mutagenesis in this study. We succeeded in the production of homozygous <i>OsCpn60β1</i> knockout rice plants. The <i>OsCpn60β1</i> mutant displayed a striking albino leaf phenotype and was seedling lethal. Electron microscopy observation demonstrated that chloroplasts were severely disrupted in the <i>OsCpn60β1</i> mutant. In addition, <i>OsCpn60β1</i> was located in the chloroplast and <i>OsCpn60β1</i> is constitutively expressed in various tissues particularly in the green tissues. The label-free qualitative proteomics showed that photosynthesis-related pathways and ribosomal pathways were significantly inhibited in <i>OsCpn60β1</i> mutants. These results indicate that <i>OsCpn60β1</i> is essential for chloroplast development in rice.