Plastid gene translation is carried out in its ribosome which RNAs undergo posttranscriptional processing.Several pentatricopeptide repeat (PPR) proteins are involved in the processes.However,the mechanism underlying the regulatory mRNA processing for plastid ribosome genes remains to be elucidated.Here,we report that a rice PPR protein ALBL plays crucial role in plastid gene expression by participating in the maturation of the precursor of plastid 23S-4.5S rRNA.We isolated ALBL gene from a rice (Oryza sativa) mutant,nearly albino phenotype (albl) by map-based cloning method,and identified ALBL as a novel nucleus-encoded PPR protein with a C-terminal DYW domain,and localized to the chloroplast.Mutation of ALBL resulted in the dramatic decrease of photosynthetic proteins and abnormal chloroplasts in the seedling,plastid ribosome deficiency.albl was defected the maturation of 23S-4.5S rRNA,while significantly increased in the amount of its precursor transcripts.Based on these results,we propose that ALBL is required for plastid gene expression,participating in the maturation process of 23S-4.5S rRNA.