UPDATES

1/2010: We have completed proteomic analysis of peroxisomes from etiolated peroxisomes (glyoxysomes). Subtype-specific proteins have been identified; subcellular localization verification is underway. Proteome analysis of peroxisomes from senescent tissues is also underway.

In addition, as supplemental data to the leaf proteomics work, we confirmed the nonapeptide RVx5HF to be a bona fide new PTS2, and further confirmed the peroxisomal localization of UP6 (unknown protein 6) and GLX1 (glyoxalase 1 homolog), two proteins with possible roles in stress responses and glutathione-dependent detoxification, respectively. These data, together with results from our previous analysis of the peroxisomal proteome, reinforce the notion that peroxisomes are involved in various stress responses and suggest glutathione as a major antioxidant in plant peroxisomes. Please read our addendum: Quan S, Switzenberg R, Reumann S, and Hu J (2010). In vivo subcellular targeting analysis validates a novel peroxisome targeting signal type 2 and the peroxisomal localization of two proteins with putative functions in defense in Arabidopsis. Plant Signal & Behav 5 (2).

5/2009: We have submitted subcellular targeting data for novel leaf peroxisome proteins to TAIR to improve gene annotation. We have also donated clones for reporter constructs of the novel peroxisome proteins to ABRC.

12/2008: We finished an in-depth proteome analysis of Arabidopsis leaf peroxisomes. In total we detected 65 established plant peroxisomal proteins, 30 proteins whose association with Arabidopsis peroxisomes had been previously demonstrated only by proteomic data, and 55 putative novel proteins of peroxisomes. We tested the subcellular targeting of yellow fluorescent protein (YFP) fusions for selected proteins and confirmed the peroxisomal localization for 12 proteins containing predicted peroxisome targeting signals type 1 or 2 (PTS1/2), three proteins carrying PTS-related peptides, and four proteins that lack conventional targeting signals. We thereby established the tripeptides SLM> and SKV> as new PTS1s and the nonapeptide RVx5HF as a putative new PTS2. The 19 peroxisomal proteins conclusively identified from our study potentially carry out novel metabolic and regulatory functions of peroxisomes.

Please read our publication on leaf peroxisome proteomics: Reumann S, Quan S, Aung K, Yang P, Shrestha K, Holbrook D, Linka N, Switzenberg, R, Wilkerson C, Weber AP, Olsen LJ, and Hu J (2009). In-depth proteome analysis of Arabidopsis leaf peroxisomes combined with in vivo subcellular targeting verification indicates novel metabolic and regulatory functions of peroxisomes. Plant Physiol 150, 125-143.

6/2008: We have purified large amounts of glyoxysomes and gerontosomes and initiated proteomic analyses of these two peroxisomal variants. Subcellular targeting of a subset of proteins identified from both in silico Peroxisome Targeting Signal (PTS) searches and proteomic analysis of leaf peroxisomes has been done by co-expression of a peroxisomal marker protein (CFP-PTS1) and a YFP-fusion of each novel protein in tobacco leaves. Over 50% of the proteins tested were confirmed to be peroxisomal. We have also initiated identification and characterization of T-DNA insertion mutants for newly identified peroxisome genes. Follow-up studies of the physiological roles for some novel peroxisomal proteins have also been initiated.

12/2007: We have purified large quantities of leaf peroxisomes and identified peroxisomal proteins through one-dimensional gel electrophoresis followed by liquid chromatography- electrospray ionization- tandem mass spectrometry (1D GE-LC-ESI-MS/MS). We were able to identify over 150 peroxisomal proteins (known and putative), including nearly all of the known leaf peroxisomal matrix proteins and over 60 novel proteins.

6/2007: We have initiated purification and proteomic analysis of green leaf peroxisomes. We have also finished Gateway-compatible YFP reporter vector construction and the cloning of the first group of putative peroxisomal proteins into the YFP vectors. A number of the novel proteins identified from in silico and proteomics analyses were successfully confirmed to be peroxisome targeting.

10/2006: Project begins.