Plastid caseinolytic protease OsClpR1 regulates chloroplast development and chloroplast RNA editing in rice

Background Plant plastidic caseinolytic protease (Clp) is a central part of the plastid protease network and consists of multiple subunits. The molecular functions of many Clps in plants, especially in crops, are not well known. Results In this study, we identified an albino lethal mutant al3 in rice, which produces albino leaves and dies at the seedling stage. Molecular cloning revealed that AL3 encodes a plastid caseinolytic protease, OsClpR1, homologous to Arabidopsis ClpR1 and is targeted to the chloroplast. Compared with the wild type, chloroplast structure in the al3 mutant was poorly developed. OsClpR1 was constitutively expressed in all rice tissues, especially in young leaves. The OsClpR1 mutation affected the transcript levels of chlorophyll biosynthesis and chloroplast development-related genes. The RNA editing efficiency of three chloroplast genes (rpl2, ndhB, ndhA) was remarkably reduced in al3. Using a yeast two-hybrid screen, we found that OsClpR1 interacted with OsClpP4, OsClpP5, OsClpP2, and OsClpS1. Conclusions Collectively, our results provide novel insights into the function of Clps in rice.

Automated summary

This study identified an albino lethal mutant al3 in rice, which is a plastidic caseinolytic protease OsClpR1 affecting the transcript levels of chlorophyll biosynthesis and chloroplast development-related genes. The results provide novel insights into the function of Clps in rice.