A research team lead by Dr. Hsou-min Li, a Research Fellow in the Institute of Molecular Biology, recently discovered that the import of proteins into chloroplasts in plants is dependent on age, upturning the previously accepted notion that transport of proteins into chloroplasts is age-independent. These findings, which further our understanding of the aging process in plants, were published in the scholarly journal PLOS Biology on October 30, 2012.

　　Forty years of molecular biology research clearly shows that gene expression changes with age. Some genes are expressed in young organisms, and some genes are expressed in aged organisms. However, up until now it has been generally believed that inside the cell, transport of proteins is age-independent.

　　Dr. Li and colleagues investigated pea leaves of different ages and discovered, for the first time, that proteins imported into chloroplasts can be divided into three groups: one group preferentially imports into young chloroplasts, the second group has no special preference, and the third group preferentially imports into older chloroplasts. In addition, the researchers further identified a signal-peptide motif that is necessary for targeting proteins to older chloroplasts. These findings may have implications for selectively targeting proteins into organelles of aging tissues.

　　The complete article entitled "Differential Age-Dependent Import Regulation by Signal Peptides" can be found at the PLOS Biology journal website at: http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001416.

　　The complete list of authors is: Yi-Shan Teng, Po-Ting Chan, and Hsou-min Li.