Abstract
Sugarcane can suffer severe yield losses when affected by leaf scald, a disease caused by Xanthomonas albilineans. This bacterial pathogen colonizes the vascular system of sugarcane, which can result in reduced plant growth and plant death. In order to better understand the molecular mechanisms involved in the resistance of sugarcane to leaf scald, a comparative proteomic study was performed with two sugarcane cultivars inoculated with X. albilineans: one resistant (LCP 85-384) and one susceptible (ROC20) to leaf scald. The iTRAQ (isobaric tags for relative and absolute quantification) approach at 0 and 48 h post-inoculation (hpi) was used to identify and annotate differentially expressed proteins (DEPs). A total of 4295 proteins were associated with 1099 gene ontology (GO) terms by GO analysis. Among those, 285 were DEPs during X. albilineans infection in cultivars LCP 85-384 and ROC20. One hundred seventy-two DEPs were identified in resistant cultivar LCP 85-384, and 113 of these proteins were upregulated and 59 were downregulated. One hundred ninety-two DEPs were found in susceptible cultivar ROC20 and half of these (92) were upregulated, whereas the other half corresponded to downregulated proteins. The significantly upregulated DEPs in LCP 85-384 were involved in metabolic pathways, the biosynthesis of secondary metabolites, and the phenylpropanoid biosynthesis pathway. Additionally, the expression of seven candidate genes related to photosynthesis and glycolytic pathways, plant innate immune system, glycosylation process, plant cytochrome P450, and non-specific lipid transfer protein was verified based on transcription levels in sugarcane during infection by X. albilineans. Our findings shed new light on the differential expression of proteins in sugarcane cultivars in response to infection by X. albilineans. The identification of these genes provides important information for sugarcane variety improvement programs using molecular breeding strategies.
Highlights
Sugarcane (Saccharum spp. hybrids) is an important food and bioenergy source and a significant component of the economy in more than 100 countries in the tropics and subtropics [1]
Overview of Proteomic Profiling of Sugarcane Infected by X. albilineans isobaric tags for relative and absolute quantification (iTRAQ) analysis revealed 574,559 and 548,154 total spectra, 21,703 and 19,350 unique peptides, and 6126 and 5463 proteins for the non-infected control plants (R0_CK and S0_CK) and the plants inoculated with X. albilineans (R48_Xa and S48_Xa), respectively
Among the 2231 proteins annotated in the biological process category, most proteins were distributed into the oxidation-reduction process (525 proteins, 24%), the metabolic process (280 proteins, 13%), proteolysis (163 proteins, 7%), and the carbohydrate metabolic process (156 proteins, 7%)
Summary
Sugarcane (Saccharum spp. hybrids) is an important food and bioenergy source and a significant component of the economy in more than 100 countries in the tropics and subtropics [1]. A BAC (bacterial artificial chromosome)-based monoploid genome sequence of cultivar R570 [5] and a genome sequence of haploid S. spontaneum clone AP85–441 were recently reported [3]. These two genome sequences included 25,316 and 35,525 protein-coding genes, respectively. A polyploid sugarcane genome sequence of cultivar SP80–3280 from Brazil was assembled, and this genome was composed of a gene space of 373,869 putative genes [6] These data provide important reference sequence information in the post genomics era [4]
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