The persimmon(Diospyros oleifera Cheng)genome provides new insights into the inheritance of astringency and ancestral evolution

Persimmon(Diospyros kaki)is an oriental perennial woody fruit tree whose popular fruit is produced and consumed worldwide.The persimmon fruit is unique because of the hyperaccumulation of proanthocyanidins during fruit development,causing the mature fruit of most cultivars to have an astringent taste.In this study,we obtained a chromosome-scale genome assembly for‘Youshi’(Diospyros oleifera,2n=2x=30),the diploid species of persimmon,by integrating Illumina sequencing,single-molecule real-time sequencing,and high-throughput chromosome conformation capture techniques.The assembled D.oleifera genome consisted of 849.53 Mb,94.14%(799.71 Mb)of which was assigned to 15 pseudochromosomes,and is the first assembled genome for any member of the Ebenaceae.Comparative genomic analysis revealed that the D.oleifera genome underwent an ancientγwhole-genome duplication event.We studied the potential genetic basis for astringency development(proanthocyanidin biosynthesis)and removal(proanthocyanidin insolublization).Proanthocyanidin biosynthesis genes were mainly distributed on chromosome 1,and the clustering of these genes is responsible for the genetic stability of astringency heredity.Genome-based RNA-seq identified deastringency genes,and promoter analysis showed that most of their promoters contained large numbers of low oxygen-responsive motifs,which is consistent with the efficient industrial application of high CO2 treatment to remove astringency.Using the D.oleifera genome as the reference,SLAF-seq indicated that‘Youshi’is one of the ancestors of the cultivated persimmon(2n=6x=90).Our study provides significant insights into the genetic basis of persimmon evolution and the development and removal astringency,and it will facilitate the improvement of the breeding of persimmon fruit.

Transcriptional regulation of fleshy fruit texture

Fleshy fruit texture is a critically important quality characteristic of ripe fruit.Softening is an irreversible process which operates in most fleshy fruits during ripening which,together with changes in color and taste,contributes to improvements in mouthfeel and general attractiveness.Softening results mainly from the expression of genes encoding enzymes responsible for cell wall modifications but starch degradation and high levels of flavonoids can also contribute to texture change.Some fleshy fruit undergo lignification during development and post-harvest,which negatively affects eating quality.Excessive softening can also lead to physical damage and infection,particularly during transport and storage which causes severe supply chain losses.Many transcription factors(TFs)that regulate fruit texture by controlling the expression of genes involved in cell wall and starch metabolism have been characterized.Some TFs directly regulate cell wall targets,while others act as part of a broader regulatory program governing several aspects of the ripening process.In this review,we focus on advances in our understanding of the transcriptional regulatory mechanisms governing fruit textural change during fruit development,ripening and postharvest.Potential targets for breeding and future research directions for the control of texture and quality improvement are discussed.

Research advance in regulation of fruit quality characteristics by microRNAs

MicroRNAs(miRNAs)are short(19-24 nucleotides in length)noncoding RNAs that have a profound effect on gene expression.By completely or almost perfectly base-pairing with their individual target mRNAs they cause mRNA cleavage or repression of translation.As important regulators,miRNAs plays an important role in the regulation of fruit quality.Extensive studies have been reported in fruits,however current studies are mostly focused on the identification of miRNAs and the prediction and validation of target genes.This review summarizes research progress on the role of miRNAs in regulating fruit ripening and senescence and quality characteristics,such as coloration,flavor metabolism,and texture for providing information for future research.