| Eucalyptus spp. being of versatile usage, is considered to be fast-growing andhigh-yielding trees resembling to pine and poplar by United Nations Food andAgriculture Organization. Calonectria spp. with numerous species, wide globaldistribution and strong pathogenicity, is the pathogen of Cylindrocladium leaf blight,which is the one of the most growing threats to Eucalyptus plantation and nursery intropic and subtropic areas. How Eucalyptus spp. responses to infection by Calonectriaplays an important role in guiding the selection for excellent Eucalyptus spp. cultivarresistant to Calonectria spp.. To date, related researches exploring defense mechanismof Eucalyptus to Calonectria spp. mainly focuses on the level of morphologicalstructure, physiology and biochemistry, rare on the protein and gene level. In thispaper, proteomics and transcriptomics were used to explore the impact of Ca.pseudoreteaudii on E. urophylla×E. tereticornis at the level of differential expressedgene and protein. At the same time, Calonectria spp. collected from Fujian Provincewere identified employing morphological characteristics and phylogenetic inference,and the pathogenicity was tested. The preliminary results showed as follows:(1) For the purpose of understanding dynamic distribution of Calonectria spp. inFujian Province, representive Calonectria spp collected from Eucalyptus commercialplantations and nurseries were identified as Ca. pseudoreteaudii、Ca. pseudocolhouniiand Ca. kyotensis employing morphological characteristics combining with DNAsequence comparisons for the β-tubulin, histone H3and translation elongationfactor-1α gene regions. And it would pay contribution to Cylindrocladium leaf blightprevention by means of forecasting and quarantine. Pathogenicity tests showed thatCa. pseudoreteaudii、Ca. pseudocolhounii and Ca. kyotensis were able to infectEucalyptus with different pathogenicity, and their pathogenicity manifested as Ca.pseudoreteaudii＞Ca. pseudocolhounii＞Ca. kyotensis. Pathogenicity tests wouldpropose that resistant cultivar to Calonectria spp. should be chosen for plantationfrom now on.(2) Leaves of E. urophylla×E. tereticornis M1after inoculating with Ca.pseudoreteaudii for12h and24h were used for testing materials. Both of the leaves’transcriptomics were analyzed by RNA-seq. The sequencing reads were then mappedto the reference genome sequence of Eucalyptus grandis. After the functionalannotation of the genes, the GO and KEGG Pathway enrichment analysis were carriedout, and six differentially expressed genes were confirmed by quantitative real-timePCR (qRT-PCR). The results showed as follows:①For12h and24h after inoculation,the differentially expressed genes were6956and7422respectively, among which thefold changes over15were54and117. Digital expressed genes involving inenrichment pathway were26at12h after inoculation, while24h were28, and most ofthem were closely related with the plant’s response to stress.②Genes relating with respiratory metabolism were up-regulated, including embden-meyerhof-parnas pathway,pentose phosphate pathway and tricarboxylic acid cycle, which suggested that E.urophylla×E. tereticornis M1was likely to strengthen the respiratory to defense theinfection of Ca. pseudoreteaudii.③Several signaling pathways regulateddisease-resistance were activated after the inoculation of Ca. pseudoreteaudii, they wereSApathway, JA/ET pathway, BRs pathway, CTK and Auxin pathway and MAPK signalpathway. Genes involving in CTK and Auxin pathways were down-regulated. Therefore,the paper suggested that being as fast-growing tree, E. urophylla×E. tereticornis, mayslow down the growth rate to enhance resistance against Ca. pseudoreteaudii.④Theexpression level of a variety of genes related to antioxidation altered under the stressof Ca. pseudoreteaudii. It demonstrated that E. urophylla×E. tereticornis M1maymediate the expression of antioxidant to maintain the status of the balance of reactiveoxygen species (ROS).⑤Genes involved in phenylpropanoid metabolism andisoprenoid metabolism were up-regulated, which indicated that E. urophylla×E.tereticornis M1may protect the plants from Ca. pseudoreteaudii by accelerating thesynthesis of secondary substances, such as lignin, phenolic compounds, andisoprenoid compounds.⑥RIN4, a negative regulator associated with plant-pathogeninteraction, was found down-regulated, and RPM1which was a positive regulator inthe downstream was up-regulated. So the paper inferred that this may contribute to theresistance of E. urophylla×E. tereticornis M1to Ca.pseudoreteaudii.(3)On the basis of transcriptomes, the differential proteomics of the leaves,inoculated with Ca. pseudoreteaudii, were analyzed by iTRAQ technology, and GO andpathway analysis were further performed to determine which differentially expressedproteins were remarkably enriched. Then, the correlation analysis between proteomicsand transcriptomes were conducted. Finally, disease resistant proteins, obviouslyassociated with transcriptome, were screened. The results were as followed:①Differentially expressed proteins and their genes of the leaves were all enriched onphenylalanine metabolism, flavonoid biosynthesis, Linoleic acid metabolism andmetabolic pathways after infection with Ca. pseudoreteaudii for12h, while enriched onLinoleic acid metabolism, biosynthesis of secondary metabolites, terpenoid backbonebiosynthesis, galactose metabolism, stilbenoid, diarylheptanoid and gingerolbiosynthesis, flavonoid biosynthesis and metabolic pathways after inoculated with Ca.pseudoreteaudii for24h. Those pathways were directly or indirectly related withdisease reistance.②The correlation analysises showed that after infection with Ca.pseudoreteaudii for12h, the correlation between the proteomics and transcriptomeswas low (r=0.2935), while the24h was higher (r=0.6985).③128differential proteinswith high correlation were screened, and65proteins were down-regulated and63up-regulated. For those proteins, some were continuously expressed induced by Ca.pseudoreteaudii, some were specifically expressed after induced by Ca. pseudoreteaudiiat12hor24h. Most differentialproteinswere closelyrelatedto plant’s stress resistance, such asglutathione S-transferases, phenylalnine ammonialyase, allene oxide synthase,diphosphomevalonate decarboxylase, pathogenesis-related proteins, peroxidase,chitinase, lipoxygenase, dehydrins, subtilisin and sieve element occlusion. |
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