Secretome Analysis Reveals anArabidopsisLipase Involved in Defense againstAlternaria brassicicola 

Abstract

The Arabidopsis thaliana secretome was analyzed by the proteomic approach, which led to the identification of secreted proteins implicated in many aspects of cell biology. We then investigated the change in the Arabidopsis secretome in response to salicylic acid and identified several proteins involved in pathogen response. One of these, a secreted lipase with a GDSL-like motif designated GDSL LIPASE1 (GLIP1), was further characterized for its function in disease resistance. glip1 plants were markedly more susceptible to infection by the necrotrophic fungus Alternaria brassicicola compared with the parental wild-type plants. The recombinant GLIP1 protein possessed lipase and antimicrobial activities that directly disrupt fungal spore integrity. Furthermore, GLIP1 appeared to trigger systemic resistance signaling in plants when challenged with A. brassicicola, because pretreatment of the glip1 mutant with recombinant GLIP1 protein inhibited A. brassicicola-induced cell death in both peripheral and distal leaves. Moreover, glip1 showed altered expression of defense-and ethylene-related genes. GLIP1 transcription was increased by ethephon, the ethylene releaser, but not by salicylic acid or jasmonic acid. These results suggest that GLIP1, in association with ethylene signaling, may be a critical component in plant resistance to A. brassicicola.

Identification and profiling of salinity stress-responsive proteins in Sorghum bicolor seedlings

“…Such observed spotting patterns have been reported in previous studies [32,38,49,50]. Multiple spotting of the same protein in different locations on a 2-DE gel may be a reflection of protein isoforms due to PTMs or multigene families, products of proteolytic activities, the presence of multiple subunits of a single protein and/or the chemical modification of proteins during sample preparation [51].…”

Arabidopsis Cell Death in Compatible and Incompatible Interactions with Alternaria brassicicola

“…pekinensis predict a high degree of sequence similarity among Arabidopsis genes and their orthologs in Korean cabbage (Hong et al, 2006). Several works have already been undertaken to analyze the incompatible interaction between Alternaria brassicicola and Arabidopsis wild types and to explain the breakdown of this incompatibility in several mutants that lack of specific defense signaling pathways (Kagan and Hammerschmidt, 2002;Mengiste et al, 2003;Oh et al, 2005;Thomma et al, 1998;.…”

MODIFIED VACUOLE PHENOTYPE1 Is an Arabidopsis Myrosinase-Associated Protein Involved in Endomembrane Protein Trafficking

“…The mvp1-1 (G57E) mutant clone was generated by mutagenic PCR using the following primers with one mismatch (lowercase): 5#-GACGCTCTTTGTGTTCGaAGATGGTCTTTACGACGCC-3# (forward) and 5#-GTCGTAAAGACCATCTtCGAACACAAAGAGCGTCTG-3# (reverse). Protein expression was induced and lipase activity was measured as described using GLIP1 and glip1 recombinant proteins as positive and negative controls, respectively (Oh et al, 2005). To assay for MVP1 lipase activity in E. coli, we performed assays as described previously (Sommer et al, 1997).…”

“…Cloning and protein expression were performed as described previously (Oh et al, 2005) using PCR primers with appended sequences for BamHI and XhoI cloning sites (lowercase and underlined): 5#-gagaggatccATGCTTTTGA-TACCTTC-3# (forward) and 5#-gagactcgagTTATATCATAAAGGAG-3# (reverse). The mvp1-1 (G57E) mutant clone was generated by mutagenic PCR using the following primers with one mismatch (lowercase): 5#-GACGCTCTTTGTGTTCGaAGATGGTCTTTACGACGCC-3# (forward) and 5#-GTCGTAAAGACCATCTtCGAACACAAAGAGCGTCTG-3# (reverse).…”

“…We fused both wild-type and mutant proteins to GST tags to facilitate purification after expression in Escherichia coli. Recombinant MVP1 protein was isolated and purified along with the secreted GDSL lipase protein GLIP1 (Oh et al, 2005), which was used as a positive control. The glip1 mutant protein and GST were also expressed and used as negative controls (Supplemental Fig.…”