Preprotein import into chloroplasts depends on macromolecular machineries in the outer and inner chloroplast envelope membrane （TOC and TIC）. It was suggested that both machineries are interconnected by components o...Preprotein import into chloroplasts depends on macromolecular machineries in the outer and inner chloroplast envelope membrane （TOC and TIC）. It was suggested that both machineries are interconnected by components of the intermembrane space （IMS）. That is, amongst others, Tic22, of which two closely related isoforms exist in Arabidopsis thaliana, namely atTic22-III and atTic22-IV. We investigated the function of Tic22 in vivo by analyzing T-DNA insertion lines of the corresponding genes. While the T-DNA insertion in the individual genes caused only slight defects, a double mutant of both isoforms showed retarded growth, a pale phenotype under high-light conditions, a reduced import rate, and a reduction in the photosynthetic performance of the plants. The latter is supported by changes in the metabolite content of mutant plants when compared to wild-type. Thus, our results support the notion that Tic22 is directly involved in chloroplast preprotein import and might point to a particular importance of Tic22 in chloroplast biogenesis at times of high import rates.展开更多
Mammalian mitochondrial genome encodes a small set of tRNAs, rRNAs, and mRNAs. The RNA synthesis process has been well characterized. How the RNAs are degraded, however, is poorly understood. It was long assumed that ...Mammalian mitochondrial genome encodes a small set of tRNAs, rRNAs, and mRNAs. The RNA synthesis process has been well characterized. How the RNAs are degraded, however, is poorly understood. It was long assumed that the degradation happens in the matrix where transcription and translation machineries reside. Here we show that contrary to the assumption, mammalian mitochondrial RNA degradation occurs in the mitochondrial intermembrane space （IMS） and the IMS- localized RNASET2 is the enzyme that degrades the RNAs. This provides a new paradigm for understanding mitochondrial RNA metabolism and transport.展开更多
文摘Preprotein import into chloroplasts depends on macromolecular machineries in the outer and inner chloroplast envelope membrane （TOC and TIC）. It was suggested that both machineries are interconnected by components of the intermembrane space （IMS）. That is, amongst others, Tic22, of which two closely related isoforms exist in Arabidopsis thaliana, namely atTic22-III and atTic22-IV. We investigated the function of Tic22 in vivo by analyzing T-DNA insertion lines of the corresponding genes. While the T-DNA insertion in the individual genes caused only slight defects, a double mutant of both isoforms showed retarded growth, a pale phenotype under high-light conditions, a reduced import rate, and a reduction in the photosynthetic performance of the plants. The latter is supported by changes in the metabolite content of mutant plants when compared to wild-type. Thus, our results support the notion that Tic22 is directly involved in chloroplast preprotein import and might point to a particular importance of Tic22 in chloroplast biogenesis at times of high import rates.
基金We thank Haiteng Deng for the help on Mass Spec and Zhi Lu and Hongwei Wang for discussion. This research was supported by the Priority Research Program of the Ministry of Science and Technology 2017YFA0504600, the National Natural Science Foundation of China （Grant Nos. 31371439 and 91649103）, and Ministry of Education 1000 youth program.
文摘Mammalian mitochondrial genome encodes a small set of tRNAs, rRNAs, and mRNAs. The RNA synthesis process has been well characterized. How the RNAs are degraded, however, is poorly understood. It was long assumed that the degradation happens in the matrix where transcription and translation machineries reside. Here we show that contrary to the assumption, mammalian mitochondrial RNA degradation occurs in the mitochondrial intermembrane space （IMS） and the IMS- localized RNASET2 is the enzyme that degrades the RNAs. This provides a new paradigm for understanding mitochondrial RNA metabolism and transport.
