Changes in the Proteome of Xylem Sap in Brassica oleracea in Response to Fusarium oxysporum Stress

Abstract

Fusarium oxysporum f.sp. conlutinans (Foc) is a serious root-invading and xylem-colonizing fungus that causes yellowing in Brassica oleracea. To comprehensively understand the interaction between F. oxysporum and B. oleracea, composition of the xylem sap proteome of the non-infected and Foc-infected plants was investigated in both resistant and susceptible cultivars using liquid chromatography-tandem mass spectrometry (LC-MS/MS) after in-solution digestion of xylem sap proteins. Whole genome sequencing of Foc was carried out and generated a predicted Foc protein database. The predicted Foc protein database was then combined with the public B. oleracea and B. rapa protein databases downloaded from Uniprot and used for protein identification. About 200 plant proteins were identified in the xylem sap of susceptible and resistant plants. Comparison between the non-infected and Foc-infected samples revealed that Foc infection causes changes to the protein composition in B. oleracea xylem sap where repressed proteins accounted for a greater proportion than those of induced in both the susceptible and resistant reactions. The analysis on the proteins with concentration change > = 2-fold indicated a large portion of up- and down-regulated proteins were those acting on carbohydrates. Proteins with leucine-rich repeats and legume lectin domains were mainly induced in both resistant and susceptible system, so was the case of thaumatins. Twenty-five Foc proteins were identified in the infected xylem sap and 10 of them were cysteine-containing secreted small proteins that are good candidates for virulence and/or avirulence effectors. The findings of differential response of protein contents in the xylem sap between the non-infected and Foc-infected samples as well as the Foc candidate effectors secreted in xylem provide valuable insights into B. oleracea-Foc interactions.

Comparison of transcriptome profiles by Fusarium oxysporum inoculation between Fusarium yellows resistant and susceptible lines in Brassica rapa L.

“…These results suggest that the susceptible lines activate the JA-and ET-signaling pathways, which are effective against the necrotroph phase, but the resistant lines do not. In the case of cabbage, F. oxysporum was observed in an outer layer of a root apex in the susceptible lines at 1 day post infection (dpi) but not in the resistant lines at 1 dpi (Pu et al 2016), suggesting that the difference of transcriptome reactions in the resistant and susceptible lines becomes clear from 24 and 72 HAI, which might be consistent with the time when Foc multiplies in susceptible lines.…”

Biocontrol by Fusarium oxysporum Using Endophyte-Mediated Resistance

“…The finding that PR-5 isoforms also specifically accumulate in xylem sap of susceptible and resistant Brassica oleracea infected with Fo f.sp. conglutinans (Pu et al, 2016) further indicates a role for these proteins in controlling the proliferation of pathogenic Fo strains in the vasculature. The observation that pathogenicity-compromised Fol strains in which specific effectors are deleted trigger an >200fold induction of NP24 in the xylem sap provides additional support for this hypothesis (Gawehns et al, 2015).…”

“…Inoculation of resistant cabbage roots with Fo f.sp. conglutinans also resulted in marginal colonization of the vasculature and fungal proteins were not identified in the xylem sap either (Pu et al, 2016).…”

Proteomic analysis of banana xylem sap provides insight into resistant mechanisms to Fusarium oxysporum f. sp. cubense Tropical Race 4

“…The signal molecules are vital for plant adaption to abiotic and biotic stress [32,33]. The xylem sap proteomics have been applied to characterize the processes associated with plant defense to Fusarium wilt [34][35][36][37][38]. However, to our knowledge, there is no research to analyze changes in banana xylem sap proteins response to TR4 to date.…”