Characterization of a gene regulatory network underlying astringency loss in persimmon fruit
Transcriptome analysis of a persimmon population segregating for an astringency trait in fruit suggested central roles for a limited number of transcriptional regulators in the loss of proanthocyanidin accumulation.
Persimmon (Diospyros kaki; 2n = 6x = 90) accumulates a large amount of proanthocyanidins (PAs) in its fruit, resulting in an astringent taste. Persimmon cultivars are classified into four types based on the nature of astringency loss and the amount of PAs at maturity. Pollination constant and non-astringent (PCNA)-type cultivars stop accumulating PAs in the early stages of fruit development and their fruit can be consumed when still firm without the need for artificial deastringency treatments. While the PCNA trait has been shown to be conferred by a recessive allele at a single locus (ASTRINGENCY; AST), the exact genetic determinant remains unidentified. Here, we conducted transcriptome analyses to elucidate the regulatory mechanism underlying this trait using developing fruits of an F1 population segregating for the PCNA trait. Comparisons of the transcriptomes of PCNA and non-PCNA individuals and hierarchical clustering revealed that genes related to the flavonoid pathway and to abiotic stress responses involving light stimulation were expressed coordinately with PA accumulation. Furthermore, coexpression network analyses suggested that three putative transcription factors were central to the PA regulatory network and that at least DkMYB4 and/or DkMYC1, which have been reported to form a protein complex with each other for PA regulation, may have a central role in the differential expression of PA biosynthetic pathway genes between PCNA and non-PCNA.
KeywordsAbiotic stress Coexpression network analysis Diospyros kaki Fruit transcriptome Proanthocyanidins
CBL-interacting protein kinase
Pollination constant and non-astringent
Reads per kilobase of exon per million reads
We thank Dr. Takashi Akagi (Kyoto University) for critical advice and discussions on data interpretation. We also appreciate bioinformatics support from Dr. Luca Comai and Dr. Isabelle M Henry (UC Davis).
Compliance with ethical standards
This work was supported by Grant-in-Aid for JSPS Research Fellow to SN (Grant number JP16J10408), and for Scientific Research (B) to KY (Grant number JP16H04876) from Japan Society for the Promotion of Science.
Conflict of interest
The authors declare that they have no conflicts of interest.
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