Protein Targeting and Vesicular Trafficking
Juárez-Díaz, Javier Andres , Guevara-García, Arturo , León-Mejía, Patricia , Vázquez-Santana, Sonia , Márquez-Guzmán, Judith , Cruz-García, Felipe .
A non-classical internal signal promotes the secretion of a thioredoxin h in plants.
Most of the secretion proteins are exported by the endoplasmic reticulum-Golgi (ER/Golgi) pathway. However, there are several evidences, in yeast and animals, indicating that there is a non-classical secretion route as well, which is also independent of an orthodox signal peptide. Thioredoxins h (Trx h) are assumed as cytoplasmic proteins. Nevertheless, there are some Trx h with non-conserved N-terminal extensions, which a few have been tested as signals for secretion or organelle targeting. We recently reported a Trx h, NaTrxh, which is a secretion protein in Nicotiana alata without any apparent signal peptide. NaTrxh reduces the S-RNases in vitro and co-localizes with them in the extracellular matrix of the stylar transmitting tract of N. alata. In addition, we proved by transient expression assays in A. thaliana and Nicotiana benthamiana leaves, that NaTrxh sequence contains all the required information to direct its secretion. Further analysis, using a deletion approach, indicates that the first 16 residues, which are predicted by some algorithms as a putative signal peptide, do not interfere with the secretion of an NaTrxh:GFP fusion protein. However, if the next 11 residues are also deleted, the NaTrxh:GFP fusion protein accumulates in the cytoplasm. These results suggest that there is an internal secretion signal that promotes NaTrxh secretion, a phenomenon poorly described in plants. Thus, our research is focusing on studying: 1) the identification of the minimal NaTrxh internal residues involved in its secretion in plants and 2) if NaTrxh secretion is through the ER/Golgi pathway or if this happens by a non-classical secretory mechanism.
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1 - Facultad de Ciencias, Universidad Nacional Autónoma de México, Biología Comparada, Circuito Exterior s/n, Ciudad Universitaria, México, D. F., 04510, Mexico
2 - Instituto de Biotecnología, Universidad Nacional Autónoma de México, Biología Molecular de Plantas
3 - Facultad de Ciencias, Universidad Nacional Autónoma de México, Biología Comparada
4 - Facultad de Química, Universidad Nacional Autónoma de México, Bioquímica y Biología Molecular de Plantas
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM