β-Aminobutyric Acid Priming Acquisition and Defense Response of Mango Fruit to Colletotrichum gloeosporioides Infection Based on Quantitative Proteomics

Abstract

β-aminobutyric acid (BABA) is a new environmentally friendly agent to induce disease resistance by priming of defense in plants. However, molecular mechanisms underlying BABA-induced priming defense are not fully understood. Here, comprehensive analysis of priming mechanism of BABA-induced resistance was investigated based on mango-Colletotrichum gloeosporioides interaction system using iTRAQ-based proteome approach. Results showed that BABA treatments effectively inhibited the expansion of anthracnose caused by C. gleosporioides in mango fruit. Proteomic results revealed that stronger response to pathogen in BABA-primed mango fruit after C. gleosporioides inoculation might be attributed to differentially accumulated proteins involved in secondary metabolism, defense signaling and response, transcriptional regulation, protein post-translational modification, etc. Additionally, we testified the involvement of non-specific lipid-transfer protein (nsLTP) in the priming acquisition at early priming stage and memory in BABA-primed mango fruit. Meanwhile, spring effect was found in the primed mango fruit, indicated by inhibition of defense-related proteins at priming phase but stronger activation of defense response when exposure to pathogen compared with non-primed fruit. As an energy-saving strategy, BABA-induced priming might also alter sugar metabolism to provide more backbone for secondary metabolites biosynthesis. In sum, this study provided new clues to elucidate the mechanism of BABA-induced priming defense in harvested fruit.

Keywords: anthracnose; fruit; priming; proteome; stress; β-aminobutyric acid.

Figure 1

Outline of the platform used for β-aminobutyric acid (BABA)-priming mechanism investigation. (a) Mango fruit were non-primed (I) or BABA-primed (II) before inoculation of C. gloeosporioides during postharvest storage; (b) Visual image of anthracnose disease in mango fruit after different treatments; (c) Lesion diameter of mango fruit after different treatments.

Figure 2

Effect of BABA treatment on total phenolics (a), total flavonoids (b), lignin content (c), SA (d), and JA (e) content in mango fruit. Data presented are means ± standard errors (n = 3).

Figure 3

Effect of BABA treatment on β-1,3-glucanase (GLU) (a), phenylalanine ammonia lyase (PAL) (b) and chitinase (CHI) (c) activities in mango fruit. Data presented are means ± standard errors (n = 3).

Figure 4

Differentially regulated proteins at priming stage. (a) The number of proteins regulated by priming at 18 h; (b) Gene Ontology (GO) analysis of the proteins differentially regulated at priming stage.

Figure 5

Differentially expressed proteins in response to C. gloeosporioides infection in primed fruit and non-primed plants. (a) Venn diagrams showing the number of differentially regulated proteins. BABA+ represents BABA + C. gloeosporioides fruits while Water+ represents Water + C. gloeosporioides fruits. (b) GO analysis of the proteins only differentially regulated in BABA primed fruit. (c) GO analysis of the proteins differentially expressed between BABA+ C. gloeosporioides and Water + C. gloeosporioides. (d) Protein–protein interaction (PPI) analysis of proteins only differentially regulated in BABA primed fruit. (e) PPI analysis of proteins differentially expressed between BABA + C. gloeosporioides and Water + C. gloeosporioides. Red color in D and E represented upregulation while green color represented downregulation.

Figure 6

Proteins that were differentially regulated in BABA-primed fruit at priming stage and post-challenge priming stage were graphically analyzed and visualized using the MapMan. Proteins that were differentially regulated in BABA-primed fruit at priming stage involved in cell defense (a) and biotic stress (b); proteins that were differentially regulated in BABA-primed fruit at post-challenge priming stage involved in cell defense (c) and biotic stress (d). Up-regulated proteins were presented in red while down-regulated proteins in blue.

Figure 7

Effect of BABA treatment on expression level of selected genes in mango fruit.

Figure 8

Presumptive model depicting the BABA priming defense mechanism. nsLTP: non-specific lipid-transfer protein; UGT: UDP-glycosyltransferase; CHI: chitinase; PR: Pathogenesis protein; NPR1: none expressor of pathogenesis-related genes; CDPK: calcium-dependent protein kinases; DAGK: diacylglycerol kinase; MLP: major latex protein; HDA5: histone deacetylase 5; VPE: vacuolar processing enzyme; CP15A: cysteine proteinase 15A; Clp: ATP-dependent Clp protease; ASR: ABA-stress-ripening; PPI1: proton pump-interactor 1; DRP: desiccation-related protein; PAL: phenylalanin ammonia-lyase; 4CL: 4-coumarate-CoA ligase; TAL: thaumatin-like protein; CAT: catalase; TRX: thioredoxin; GRX: glutaredoxin; GPX: glutathione peroxidase; MDH: malate dehydrogenase; ENO: enolase; POD: peroxidase; PSY: Phytoene synthase; ZDS: ζ-carotene desaturase. Red arrow indicates upregulation while green arrow indicates downregulation in BABA-treated mango fruit.