Sichao Yang

SUMMARY: Persimmon fruits accumulate substantial amounts of proanthocyanidins (PAs), with soluble PAs causing a dry or puckering sensation in the mouth when consumed. Acetaldehyde, an important volatile compound, reacts with soluble PAs to form insoluble PAs, leading to the natural deastringency of the fruits of the Chinese Pollination Constant Non‐astringent (C‐PCNA) persimmon at ripening. In this study, a DkALDH (aldehyde dehydrogenase) gene belonging to subfamily 10 was revealed to be localized to the tonoplast and plasma membrane. Following transient expression experiments, we observed that DkALDH10 negatively regulates the conversion of soluble PAs into insoluble PAs. Furthermore, the stable transformation of DkALDH10 confirmed that its overexpression reduced the acetaldehyde content and thereby inhibited the conversion of soluble PAs into insoluble PAs, whereas the silencing of DkALDH10 increased the acetaldehyde content and consequently promoted the conversion of soluble PAs into insoluble PAs. Notably, microRNA143c from the small RNA libraries of ‘Eshi 1’ (C‐PCNA) fruit was predicted to target the DkALDH10 gene. The expression patterns of the transcripts of miR143c and DkALDH10 differed during the full fruit development stages of ‘Eshi 1’, and miR143c could cleave DkALDH10 at positions 10–11 bp according to RLM‐5′ RACE analysis and GFP signal detection. Transient expression and stable transformation experiments demonstrated that miR143c negatively regulates the expression of DkALDH10 , thereby influencing the conversion of soluble PAs into insoluble PAs through the modulation of acetaldehyde levels in persimmon. Collectively, our results indicate that miR143c suppresses the expression of DkALDH10 , positively regulating the natural deastringency of C‐PCNA persimmon. This finding provides a potential strategy for genetically manipulating the deastringency of C‐PCNA persimmon fruit.

The ecological region and training system are critical in determining an orchard’s microclimate and, ultimately, the quality and yield of the fruit produced. However, few studies have addressed the effects of their interactions on the commodity properties preferred by consumers, including appearance, flavor, and nutritional components. This study was conducted in distinct ecological regions at the county scale, with two classic cultivation modes (a traditional freestanding system with natural grassing and fruit without bagging and a flat-type trellis system with floor covering and fruit bagging) used for investigation and testing in 2020 and 2024, respectively. Significant differences in internal and external quality attributes were observed between the two groups. A sensory analysis showed that an increase in the soluble solid content and a better fruit appearance were strongly associated with higher purchase intentions. By integrating meteorological parameters, it was also found that temperature and air humidity during the month before harvest were associated with the pear phytochemical and metabolomic profiles. Planting site had a particularly notable effect on quality attributes and sensory experience, with low-latitude-harvested samples under cultivation mode 1 clustering together and showing higher overall scores, while cultivation mode 2 may be more suitable for high-latitude areas. Our results pave the way for making precise recommendations for the selection of suitable planting sites and optimum cultivation modes in Jiangxi Province to achieve high-quality ‘Cuiguan’ pears and fully exploit their planting potential.

Persimmon as a type of fruit is divided into pollination-constant and non-astringent (PCNA) persimmon, which can lose its astringency naturally during fruit ripening, and non-PCNA persimmon. Its soluble sugars include the essential components that determine the flavor of the persimmon fruit. However, the underlying regulatory networks that modulate the metabolism of soluble sugar in persimmon fruit remain largely unknown. In this work, three stages (10, 15, and 20 weeks after bloom) of Chinese PCNA ‘Luotian tianshi’ fruit growth were used as experimental models to reveal the molecular mechanism of soluble sugar metabolism via the combination of the transcriptome and the metabolome. Here, 21 kinds of soluble sugars were detected, with sucrose, glucose, and fructose verified as the main soluble sugars in the persimmon fruits. We obtained 59.42 Gb of clean data via transcriptome sequencing, and the maximum number of differentially expressed genes (9098) was found in the 20 W vs. 10 W groups, of which 2513 were up-regulated and 3811 were down-regulated. The KEGG enrichment analysis showed that 37 up-regulated and 71 down-regulated differentially expressed genes were enriched for starch and sucrose metabolism in the 20 W vs. 10 W groups. The metabolome and transcriptome association analysis showed that the differentially expressed genes (malZ, INV, SPS, scrK, ISA, β-AMY, TPS, otsB, and TREH) were significantly correlated with the content of differentially accumulated metabolites (such as sucrose, glucose, and fructose), indicating that they may play important roles in the metabolism of the soluble sugars in persimmon. Overall, this study provides valuable insights into the metabolism pattern of high sugar accumulation in persimmon fruit.

Cultivated persimmon (Diosspyros kaki Thunb.) is a hexaploid (mostly) or a nonaploid with high heterozygosity, hindering molecular genetic studies on proanthocyanidin (PA) metabolism, which is a major trait for persimmon astringency. Recently, one of its wild diploid relative species, oily persimmon (Diospyros oleifera), has been assembled with a chromosome-level reference. Thus, oily persimmon is now regarded as a model plant for discovering new genes associated with PA metabolism, which is highly accumulated in the fruits of this genus. In our study, we identified genome-wide microRNAs (miRNAs) and their precursor sequence based on the chromosome-scale genome of oily persimmon and the miRNA database of “Eshi 1” according to the sequence alignment and secondary structure accession. The targets were predicted on the psRNATarget software based on the genome CDS database. The size, conservation, diversity, stem-loop hairpin structures, and genome location of miRNA or the precursor sequence were analyzed by bioinformatics tools. The promoter elements of the miRNA genes were predicted on the promoter-2.0 software, which indicated that the abundant cis-acting elements were light responsiveness, promoter, and enhancer regions. The qRT-PCR assay was performed to elucidate the potential expression patterns of precursor miRNA and their targets during fruit development, and one target gene, DkMYB22, of miR2911 was verified to promote the conversion of soluble tannins into insoluble tannins involved in the deastringency in persimmons. Together, this study provides a robust foundation for further functional verification of these miRNAs associated with the natural deastringency process in persimmon, thereby facilitating advancements in persimmon fruit breeding.

Persimmon (Diospyros kaki) is a worldwide fruit cultivated mainly in the East Asia, Mediterranean, Caucasus, Latin America, and Oceania regions. This fruit contains abundant proanthocyanidins (PAs, also called condensed tannins), whose biosynthesis is the main cause of fruit astringency. As the original centre and top producing country, China has discovered a unique type with desirable natural deastringency, the Chinese pollination-constant non-astringent (C-PCNA) persimmon. Studies have revealed that the C-PCNA trait is controlled by a single and dominant locus, which differs from that of another type, the Japanese PCNA type, with recessive loci. In the C-PCNA type, accumulating evidence has shown that the astringency removal process involves two pathways (“dilution effect” and “coagulation effect”). Moreover, molecular marker-assisted selection (MAS) for the natural deastringency trait locus in C-PCNA has been used to test the non-astringency/astringency trait of hybrid offspring at the seedling stage. Importantly, persimmon can bear male flowers, female flowers, and perfect flowers, but sex-linked MAS has been developed for female-only persimmon. This sex-linked MAS, together with astringency-linked MAS and embryo rescue technology, may even shorten the conventional cross-breeding period of about 2–3 years. In addition, recently studies have established a stable genetic transformation system for persimmon transgenic improvement. Despite these efforts, how synthetic PAs and metabolism pathways lead to a deastringent trait remains unclear for persimmon. Thus, our review summarizes the latest research progress on the natural deastringency mechanism in C-PCNA, and we provide a new viewpoint for the genetic improvement of persimmon breeding in China.

MicroRNAs (miRNAs) are endogenous noncoding small RNAs containing 21–24 nucleotides (nt) that regulate gene expression precisely and efficiently at the posttranscriptional level through the negative regulation of target messenger RNA (mRNA) expression, such as translational inhibition or degradation. Likewise, as a controlling element, miRNA itself is regulated by a variety of factors when performing its basic purposes, such as SNP detection, miRNA purging, methylation, and the circadian clock in model crops. In current years, miRNA-mediated controls have been intensely investigated in horticultural plants, leading to the discovery of numerous novel mechanisms that exhibit significantly greater mechanistic complexity and distinctive regulatory properties than those explored in model species. In fruit crops, miRNAs play a crucial role corresponding to various biological, metabolic functions and environmental challenges, including growth, expansion, response to biotic and abiotic stress, signaling of growth hormones, and the regulation of secondary product metabolism. In this study, we appraisal the current improvement of small regulatory RNA research in fruit crops, emphasizing miRNA mechanisms and their correlation with key trait rule. Considering that miRNAs engaged in the regulation of all aspects of fruit tree life activities, we focus here on their biosynthesis, target genes, function and regulatory network, as well as the mechanistic connection among them, to provide a theoretic base and breakthrough for upcoming exploration on miRNAs in fruit plants.

Persimmon (Diospyros kaki Thunb.) is becoming a fruit that is used worldwide because it contains high nutritional and medicinal value. However, the trait evaluation of persimmon is still needed and is critical for marketing and breeding, especially in China. Here, we evaluated thirteen quality indicators (fruit weight, horizontal length, vertical length, firmness, titratable acid content, vitamin C content, flavonoid content, anthocyanin content, soluble sugar content, pectinase activity, soluble protein content, tannin content, and tannin cell size) in six Chinese pollination-constant, astringent (PCA) persimmon cultivars (‘Jinxi 3′, ‘Ganfang 1′, ‘Poyang 5′, ‘Poyang 6′, ‘Yifeng 1′, and ‘Yifeng 3′) and a Japanese pollination-constant non-astringent (PCNA) persimmon cultivar (‘Youhou’). The quality indicator data were normalized and subjected to variant analysis and principal component analysis (PCA). The results showed that 10 of 13 indicators among the seven persimmon cultivars were significantly different, and the contribution rates of the first principal component reached 40.582%. The principal component comprehensive scores for ‘Poyang 5′ and ‘Ganfang 1′ ranked second and third, respectively, and were clustered with that of ‘Youhou.’ In addition, we also measured the expression levels of three stress resistance genes and three proanthocyanidin (PA, also called condensed tannins) pathway genes in these persimmon cultivars by quantitative reverse transcription PCR (qRT—PCR). The qRT—PCR analysis of DkCBF and DkWRKY3/8 showed low resistance to cold in ‘Ganfang 1′ but stronger resistance to anthracnose. Moreover, the expression of the PA pathway genes demonstrated that the PA content in ‘Ganfang 1′ was at a moderate level in the seven varieties. Together, our study revealed relatively comprehensive profiles of persimmon quality evaluation and demonstrated that ‘Ganfang 1′ may have the potential to be used as a breeding parent for future persimmon breeding programs.