Responses of Tea Plants to Blister Blight Analyzed Using Transcriptome and Metabolome

Objective  Resistance mechanism and associated genes of tea plants in response to blister blight infection were studied based on transcriptome as well as metabolome.

Methods Differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) in leaves of healthy (CK) and blister blight-infected (TB) tea plants were compared by using both transcriptome and metabolome.

Results Between CK and TB, 1,009 DEGs associated with the cell wall metabolism and the regulations of chitinase, oxidoreductase, and xyloglucan:xyloglucanosyltransferase activities were identified by a GO enrichment analysis. The KEGG analysis showed the DEGs significantly enriched in the pathways of flavonoid biosynthesis, phenylpropanoid biosynthesis, amino sugar and nucleotide sugar metabolism, glycerolipid metabolism, and stilbenoid, diarylheptanoid, and gingerol biosynthesis. Forty-seven transcription factors in the DEGs, which belonged to 21 transcription factor families including bHLH, SBP, AP2/ERF-AP2, and MYB, might be the genes significantly involved in the resistance of a tea plant to blister blight. The 353 DAMs identified by using the widely targeted metabolomics were enriched mainly in the flavonoid biosynthesis and lysine biosynthesis as well as the alanine, aspartate, and glutamate metabolism pathways. The transcriptome and metabolome revealed significant co-enrichments in the flavonoid biosynthesis, phenylpropanoid biosynthesis, and stilbenoid, diarylheptanoid, and gingerol biosynthesis pathways. Among the selected 20 DEGs and 15 DAMs associated with the phenylpropanoids and flavonoids biosynthesis pathways, DEGs such as CSS0011741（4CL）, CSS0002940（DFR）, CSS0015968（DFR）, and CSS0010687（ANS） were upregulated, while DAMs such as phloretin, phlorizin, 4-Hydroxystyrene, P-Coumaroyl quinic acid, dihydromyricetin, epigallocatechin, and peonidin 3-O-glucoside were accumulated in the infected leaves.

Conclusion The DEGs in the phenylpropanoid and flavonoid biosynthesis pathways might play a crucial role in the response of tea plants to blister blight. And the DAMs, such as phloretin, phlorizin, and epigallocatechin, might be the secondary metabolites in tea plants that participated closely in the resistance mechanism.