the arabidopsis translocator protein (attspo) is regulated at multiple levels in response to salt stress and perturbations in tetrapyrrole metabolism拟南芥转运蛋白的蛋白质在不同层次(attspo)监管应对盐胁迫和扰动四吡咯新陈代谢.pdf

Balsemão-Pires et al. BMC Plant Biology 2011, 11:108 /1471-2229/11/108 RESEARCH ARTICLE Open Access The Arabidopsis translocator protein (AtTSPO) is regulated at multiple levels in response to salt stress and perturbations in tetrapyrrole metabolism 1,2 2,3 2 4 2 Emilia Balsemão-Pires , Yvon Jaillais , Bradley JSC Olson , Leonardo R Andrade , James G Umen , Joanne Chory2,3* and Gilberto Sachetto-Martins1* Abstract Background: The translocator protein 18 kDa (TSPO), previously known as the peripheral-type benzodiazepine receptor (PBR), is important for many cellular functions in mammals and bacteria, such as steroid biosynthesis, cellular respiration, cell proliferation, apoptosis, immunomodulation, transport of porphyrins and anions. Arabidopsis thaliana contains a single TSPO/PBR-related gene with a 40 amino acid N-terminal extension compared to its homologs in bacteria or mammals suggesting it might be chloroplast or mitochondrial localized. Results: To test if the TSPO N-terminal extension targets it to organelles, we fused three potential translational start sites in the TSPO cDNA to the N-terminus of GFP (AtTSPO:eGFP). The location of the AtTSPO:eGFP fusion protein was found to depend on the translational start position and the conditions under which plants were grown. Full-length AtTSPO:eGFP fusion protein was found in the endoplasmic reticulum and in vesicles of unknown identity when plants were grown in standard conditions. However, full length AtTSPO:eGFP localized to chloroplasts when grown in the presence of 150 mM NaCl, conditions of salt stress. In contrast, when AtTSPO:eGFP was truncated to the second or third start codon at amino acid position 21 or 42, the fusion protein co-lo