Transcriptome and metabolite profiling reveal novel insights into volatile heterosis in the tea plant (Camellia sinensis (L.) O. Kuntze)

Abstract

Abstract Background Tea aroma is a key indicator for evaluating tea quality. Although notable success in tea aroma has been achieved with heterosis breeding technology, the molecular basis underlying heterosis remains largely unexplored. Thus, the present study concentrates on the volatile heterosis of a broad “high aroma” trait using a high-throughput next-generation RNA-seq strategy and Gas Chromatography and Mass Spectrometry. Results Phenotypically, we found higher terpenoid volatile and green leaf volatile contents by Gas Chromatography and Mass Spectrometry in the F1 hybrids than in their parental lines. Volatile heterosis was obvious in both F1 hybrids. At the molecular level, the comparative transcriptomics analysis revealed that approximately 41% (9, 027 of 21, 995) of the genes showed non-additive expression, whereas only 7.83% (1, 723 of 21, 995) showed additive expression. Among the non-additive genes, 42.1% showed high parental dominance and 17.6% showed over-dominance. Among DEGs with high parental dominance and over-dominance expression patterns, KEGG and GO analyses found that plant hormone signal transduction, tea plant physiological process related pathways and most pathways associated with tea tree volatiles were enriched. In addition, we identified multiple genes (CsDXS, CsAATC2, CsSPLA2, etc.) and transcription factors (CsMYB1, CsbHLH79, CsWRKY40, etc.) that played important roles in tea aroma heterosis. Conclusion Based on transcriptome and metabolite profiling, we conclude that non-additive action plays a major role in tea aroma heterosis. Genes and transcription factors involved in tea volatiles showing over-dominance expression patterns can be considered candidate genes and provide novel clues for breeding high-aroma tea varieties.