Jiaoke Zeng

The transcriptional regulatory network underlying ethylene‐governed starch‐to‐sugar conversion remains poorly understood. We elucidated the hierarchical regulatory cascade linking ethylene signalling to starch degradation in postharvest kiwifruit. Ethylene treatment accelerated fruit softening, starch degradation, and soluble sugar accumulation, whereas 1‐methylcyclopropene treatment produced opposite effects in kiwifruit. Weighted gene co‐expression network analysis identified 3 β‐amylase genes ( AcBAM3.1/3.3/3.5 ) and 16 transcription factors (TFs) as highly correlated with starch‐to‐sugar conversion. AcERF10 was isolated as a direct transcriptional activator of AcBAM3.1/3.3/3.5 and the ethylene biosynthetic gene AcACO1 . AcERF10 overexpression promoted starch degradation and sugar accumulation; silencing this gene resulted in opposite phenotypes. AcERF10 was directly activated by AcERF1 and AcHAT5—TFs that are induced by ethylene. AcERF1 bound to and activated the promoter of AcHAT5 , while AcHAT5 bound to the AcERF10 promoter and interacted with AcERF10 to synergistically activate expression of AcBAMs and AcACO1 , identifying a regulatory cascade of AcERF1‐AcHAT5‐AcERF10. Overexpression of either AcERF1 or AcHAT5 promoted downstream gene expression, accelerated starch degradation, and enhanced sugar accumulation, whereas silencing of either gene suppressed these processes. This study uncovers an ethylene‐triggered, multi‐layer transcriptional regulatory network that governs starch‐to‐sugar conversion during postharvest kiwifruit ripening, providing new mechanistic insights into ethylene‐regulated fruit quality development during postharvest storage.

Sour rot significantly contributes to postharvest decay in citrus fruit. Luteolin has been utilized as a preservative in fruit, but its effectiveness and mechanisms against sour rot in citrus fruit are not well understood. In this research, luteolin was utilized to inhibit the primary sour rot fungal pathogen, Geotrichum citri-aurantii, in navel orange fruit. Luteolin treatment with 10-fold inhibitory concentration reduced lesion diameter by up to 29.38% and disease incidence by 18.18%. Additionally, luteolin treatment lowered malondialdehyde and hydrogen peroxide contents, enhanced total phenolic and flavonoid contents, maintained elevated protopectin and cellulose levels, and increased the activities of resistance-related enzymes in navel orange peel. Transcriptome analysis revealed that 241 genes exhibited differential expression between control and luteolin-treated navel peel at 3 d post-inoculation. Gene ontology analysis showed enrichment of differentially expressed genes in oxidoreductase activity, antioxidant activity, and cell wall function. Specifically, CsMUTE and CsGRXS9 were upregulated, whereas CsPE2, CsPGL3, and CsRbohD were downregulated following luteolin treatment. Through correlation analysis, strong associations were established between the CsMUTE transcription factor and structural genes. Furthermore, the phenotypes of CsMUTE transgenic citrus peel and tomato fruit suggest that CsMUTE is involved in providing resistance to Geotrichum citri-aurantii. These findings collectively show that luteolin treatment regulates sour rot by directly inhibiting fungi and triggering citrus fruit defense mechanisms. This offers new perspectives and practical strategies for environmentally friendly citrus fruit preservation.

Proanthocyanidins (PAs) display antioxidant properties and can partially delay pericarp browning in postharvested litchi (Litchi chinensis Sonn.) fruits. In this study, litchi fruit was treated with 3 g/L PA and then stored at 25 °C for 10 days. Differential metabolites and differentially expressed genes were comprehensively analyzed in litchi pericarp across four stages of browning progression. A total of 630 metabolites were identified through untargeted metabolomic analysis, with 237 of them being annotated in the kyoto encyclopedia of genes and genomes (KEGG) database. The abundance of flavonoids (kaempferol), six types of anthocyanins, cyanidins, (−)-epicatechin, and (+)-catechin in the PA biosynthetic pathway was notably reduced in PA-treated pericarp compared to that of the control fruit. Transcriptomic analysis also revealed that five genes in the phenylpropanoid biosynthesis pathways and seven genes of phenoloxidase were significantly downregulated. In addition, correlation analysis revealed significant positive correlations between the browning index and genes like LcFLS (flavonol synthase), LcANS (anthocyanidin synthase), LcUFGT (UDP-glucose:anthocyanidin 3-O-glucosyltransferase), LcPPO (polyphenol oxidase), and LcLAC7 (laccase), and a significant negative correlation with PAs and (−)-epicatechin. In conclusion, PA treatment can efficiently delay pericarp browning, mainly by reducing brown substrate accumulation and oxidation, and decreasing PA oxidation and polymerization. This study delves into the regulatory mechanisms through which PA delays litchi pericarp browning.

Postharvest quality deterioration is a major factor affecting the economic value and marketing of Nanfeng tangerines. The objective of this study was to explore the effects of luteolin treatment on the postharvest quality and antioxidant capacity of Nanfeng tangerines. We applied 1 g/L and 3 g/L luteolin to fruit after harvest and evaluated the decay rate, postharvest quality, and antioxidant capacity during a 60-day storage period at room temperature. The results indicated that, compared to untreated fruit, Nanfeng tangerines treated with 3 g/L luteolin exhibited enhanced appearance and flavor quality, as well as delayed disease incidence, during room-temperature storage. Additionally, flavor quality analysis revealed that luteolin treatment maintained high levels of titratable acid (TA) by delaying the degradation of organic acids such as citric, tartaric, succinic, ascorbic, and oxalic acids. Furthermore, luteolin treatment inhibited malondialdehyde (MDA) and H₂O₂ accumulation by enhancing the content of total phenols and flavonoids content, augmenting antioxidant enzyme activities (peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD)), and elevating the overall antioxidant capacity measured through the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging rate. Collectively, these results demonstrate that luteolin has potential as a preservative for promoting postharvest quality and antioxidant capacity. Additionally, our findings elucidate the mechanisms by which plant-derived flavonoids contribute to the preservation of freshness.

Paeonia lactiflora Pall is a traditional famous flower with long cultivated history in China, and has important medical and ornamental functions (Duan et al. 2022). In the middle of June 2022, anthracnose disease was observed nearly 25% (n=90) on P. lactiflora in Poyang County, Shangrao City, Jiangxi Province (29.00° N, 116.67° E) (Figure 1 E). The symptoms of the disease were small, round, light brown spots then grew bigger to round or irregular dark brown lesions (5 to 7 mm diameter) progressively on the leaves with disease spread (Figure 1 A). Subsequently, necrotic tissue was formed in the center and caused fade and wilt on the leaves ultimately, which reduced the medicinal and aesthetic value severely. Small pieces of diseased tissue (5 × 5 mm) were cut from the diseased junction, disinfected with 75% ethanol for 30 to 45 seconds, then 1% NaClO for 1 to 2 minutes, rinsed three times with sterile water. To identify the pathogen, tissues were placed on PDA and incubated for 3 days at 28°C. Single spore isolates were cultured on PDA, the colonies of one representative strain (SY4) were originally white with a lot of aerial mycelium after 5 to 7 days at 28°C in the incubator. The center of the colony turned greyish-white, released tiny orange-yellow particles (conidia) (Figure 1 F and 1 G), which were single, colorless, elongated ovals with rounded ends and measured 11.29 to 23.24 × 3.94 to 5.60 μm (av=15.89 μm × 4.74 μm, n=50) (Figure 1 H and 1 I). The isolate SY4 was identified to Colletotrichum fructicola based on morphological characteristics (Yang et al. 2021; Li et al. 2022b). For further molecular identification, the rDNA-ITS, actin gene (ACT), glyceraldehyde-3-phosphatedehydrogenase (GAPDH), chitin synthase (CHS) and calmodulin gene (CAL) genes were amplified and sequenced with primers of ITS1/ITS4 (Gardes et al. 1993), ACT-512F/ACT-783R, GDF/GDR (Templeton et al. 1992), CHS-79F/CHS-345R (Carbone et al. 1999) and CL1C/ CL2C (Weir et al. 2012) respectively. The accession numbers in GenBank were OP523977 (ITS-rDNA), OP547618 (ACT), OP605733 (GAPDH), OP605732 (CHS), and OP605731 (CAL). The BLAST analysis revealed that these sequences were identical more than 99% with those of C. fructicola (GenBank accession Nos. MZ437948.1, MN525803.1, MN525860.1, MZ13360.1 and ON188684.1) (Figure 2). To confirm pathogenicity, the leaves were cleaned with 75% ethanol, rinsed with sterile water. After the leaf surface was dried naturally, 20 leaves were pricked at two symmetrical places on either side of the main veins of the leaf with a sterilized inoculum needle (2.0 mm in diameter), half of the wounded leaves were inoculated with 20 μL spore suspension (1.0 × 106 spores/mL) (Figure 1 C and 1 D), while the other half were inoculated with sterile water as controls (Figure 1 B). Inoculated leaves were grown for 5 days in an incubator at 28 °C and above 90% relative humidity, repeated three times. The results demonstrated that the wounded leaves with C. fructicola showed the same signs of wilting with the original disease leaves, while control leaves remained healthy. The same fungus was reisolated from the diseased leaves which confirmed with Koch's postulates. The same fungus was re-isolated from the diseased leaves while it was not isolated from control leaves, confirmed with Koch's postulates. In China, it had been reported that C. fructicola caused anthracnose on Persea americana (Li et al. 2022a) and Myrica rubra (Li et al. 2022b). To the best of our knowledge, this is the first report of anthracnose on P. lactiflora caused by C. fructicola in China. The results will help to develop effective control strategies for anthracnose on P. lactiflora.

Sweet persimmon is native to Japan and valued for its fruit, which are high in sugar and vitamins. In October 2021, symptoms were observed on persimmon (Diospyros kaki L. cv. Yangfeng) fruits in co...

Fresh date fruits (cvs. Hillawi and Khadrawi) were harvested at the khalal stage and treated with hot water treatment (HWT) for different time durations (control, HWT-1 min, HWT-3 min, HWT-5 min, and HWT-7 min) to investigate the physicochemical characteristics, phytochemical properties, and sensory attributes. The results revealed that both date cultivars took less time to reach the tamar stage in response to HWT-7 min compared to control. However, Hillawi date fruit showed a higher fruit ripening index (75%) at HWT-3 min, while Khadrawi fruit had a higher ripening index (80%) at HWT-5 min than untreated fruit (10%). Higher weight loss and lower moisture contents were observed in Hillawi (25%) and Khadrawi (20%) date fruit as the immersion period increased in both cultivars. Moreover, soluble solid content was higher in Hillawi (11.77° Brix) in response to HWT-3 min and Khadrawi (10.02° Brix) date fruit immersed in HWT-5 min in contrast with the control group, whereas significantly lower levels of titratable acidity and ascorbic acid content were observed in Hillawi (0.162%, 0.67 mg/100 g) and Khadrawi (0.206%, 0.73 mg/100 g) date fruit in response to HWT (HWT-1 min, HWT-3 min, HWT-5 min, and HWT-7 min) than untreated fruit. Furthermore, noticeably higher levels of reducing sugar (69.83%, 57.01%), total sugar (34.47%, 31.14%), glucose (36.84%, 29.42%), fructose (33.99%, 27.61%), and sucrose (3.16%, 1.33%) were found in hot water-treated Hillawi (immersed for 3-min) and Khadrawi (immersed for 5-min) date fruit, respectively. In addition, total phenolic content, total flavonoids, total antioxidants, and total tannins were substantially superior in date fruits subjected to HWT-3 min (in Hillawi, 128 mg GAE/100 g, 61.78%, 20.18 mg CEQ/100 g) and HWT-5 min (in Khadrawi, 139.43 mg GAE/100 g, 72.84%, and 18.48 mg CEQ/100 g) compared to control. Overall, sensory attributes were recorded to be higher in Hillawi and Khadrawi date fruit after treatment for 3 min and 5 min, respectively. Our findings suggest that HWT is a promising technique that can be adopted commercially to improve fruit ripening and preserved nutritional quality of dates after harvest.