Abstract
Many organisms possess DEAD-box RNA helicase family proteins. Genetic studies mainly in yeast have revealed that DEAD-box family proteins are involved in various cellular processes including RNA splicing, ribosome biogenesis, and translation. However, there is little knowledge of the DEAD-box RNA helicases in higher plants, and in particular the physiological roles of chloroplast-localized DEAD-box helicases have never been examined. The nara12-1 (necessary for the achievement of RuBisCO accumulation) was isolated as the Arabidopsis mutant with a reduced protein level of RuBisCO, and this responsible gene encodes a DEAD-box protein RH39. Transient expression of the N-terminus of the RH39-GFP fusion protein in tobacco leaves suggested that RH39 was localized in chloroplasts. Northern blot analysis revealed that chloroplast rRNA processing was defective in nara12-1. RH39 null allele nara12-2 was embryonic lethal due to abnormal seed formation. Our results suggest that RH39 is essential for chloroplast rRNA maturation and plant development.
