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Abstract

Tea aroma is a key indicator for evaluating tea quality. Although
notable success in tea aroma improvement has been achieved with
heterosis breeding technology, the molecular basis underlying heterosis
remains largely unexplored. Thus, the present report studies the tea
plant volatile heterosis using a high-throughput next-generation RNA-seq
strategy and gas chromatography–mass spectrometry. Phenotypically, we
found higher terpenoid volatile and green leaf volatile contents by gas
chromatography–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% (9027 of 21,995) of the genes showed non-additive
expression, whereas only 7.83% (1723 of 21,995) showed additive
expression. Among the non-additive genes, 42.1% showed high parental
dominance and 17.6% showed over-dominance. Among different expression
genes 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 volatile heterosis. Based on transcriptome and
metabolite profiling, we conclude that non-additive action plays a major
role in tea volatile 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-volatile tea varieties.