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

Background Fusarium wilt is a destructive soilborne disease of banana caused by Fusarium oxysporum f. sp. cubense ( Foc ), especially Tropical Race 4 (TR4), which is a xylem-invading fungus. It was evident that xylem sap contained macromolecules, such as proteins, involved in disease-resistance processes. However, there is no research to analyze changes in banana xylem sap proteins response to TR4 to date. Methods To gain an integrated understanding of differential protein expression in banana xylem sap during TR4 infection, we performed a comparative proteomic analysis of xylem sap in resistant ‘Pahang’ and susceptible ‘Brazilian’ bananas inoculated with TR4. Results A total of 1036 proteins were detected in xylem sap of both bananas, among which some proteins are involved in ‘signal transduction’, ‘environmental adaptation’, ‘biosynthesis of secondary metabolites’ and ‘lipid metabolism’, indicating that xylem sap contained defense-related proteins. A number of 129 differential expression proteins (DEPs) were identified in 4 possible pairs between resistant and susceptible tested combinations. Of these DEPs, hypersensitive-induced response protein 1 (HIR1), E3 ubiquitin ligase (E3) might play negative roles in ‘Pahang’ response to TR4 attack, whereas chalcone isomerase (CHI), glycine-rich RNA-binding protein (GRP), carboxylesterase (CXE) and GDSL lipase (GLIP) might play positive roles in ‘Pahang’ defense against TR4 infection. Conclusions Banana xylem sap contained defense-related proteins, among which HIRP1, E3, CHI, GRP, CXE and GLIP involved in banana defense against TR4. To our knowledge, this is first report to analyze changes in banana xylem sap proteins response to TR4, which help us to explore molecular mechanisms of banana resistant to Fusarium wilt.