Calcium Treatment Alleviates Pericarp Browning of 'Nanguo' Pears by Regulating the GABA Shunt After Cold Storage

The metabolism of amino acids, AsA and abscisic acid induced by strigolactone participates in chilling tolerance in postharvest zucchini fruit

Zucchini fruit are notably susceptible to chilling injury when stored at low temperatures. The purpose of this experimental investigation was to assess the influence of strigolactone (ST) (5 μmol L-1) on mitigating chilling injury and the metabolic changes in amino acids, ascorbic acid, and abscisic acid in zucchini fruit stored at 4°C. Research findings demonstrated that ST-treated zucchini fruit displayed a significantly higher tolerance to chilling stress compared to the control group. Postharvest ST treatment led to a decrease in weight loss, accompanied by reduced levels of malondialdehyde and relative ion leakage compared to the untreated group. ST immersion significantly boosted the metabolic pathways associated with proline and arginine, affecting both the enzymatic reactions and gene expressions, thus cumulatively increasing the internal concentrations of these amino acids in zucchini fruit. Zucchini treated with ST exhibited an increased concentration of γ-aminobutyric acid (GABA) as a result of augmented activities and elevated transcriptional levels of glutamate decarboxylase (GAD), GABA transaminase (GAT), and succinate semialdehyde dehydrogenase (SSD). In the ST-treated sample, the elevated enzymatic activities and enhanced gene expressions within the ascorbic acid (AsA) biosynthesis pathway worked together to sustain AsA accumulation. The application of ST resulted in a rise in abscisic acid (ABA) concentration, which correspondingly correlated with the induction of both activities and gene expression levels of crucial enzymes involved in ABA metabolism. Our findings revealed that submerging zucchini fruit in ST could be a highly effective strategy for boosting their chilling tolerance. The alleviation in chilling injury induced by ST may be attributed to the modulation of proline, arginine, GABA, AsA and ABA metabolism.

Effects of the Combined Treatment of Trans-2-Hexenal, Ascorbic Acid, and Dimethyl Dicarbonate on the Quality in Fresh-Cut Potatoes (Solanum tuberosum L.) during Storage

Fresh-cut potatoes (Solanum tuberosum L.) are susceptible to browning and microbial contamination during storage. In this study, the effects of trans-2-hexenal (E2H), ascorbic acid (VC), dimethyl dicarbonate (DMDC), and the combined treatment of E2H, VC, and DMDC on quality deterioration in fresh-cut potatoes were investigated. The response surface methodology (RSM) demonstrated that E2H, VC, and DMDC concentrations of 0.010%, 0.65%, and 240 mg/L, respectively, were the optimum conditions for fresh-cut potato preservation. Further analysis showed that the combined treatment of E2H, VC, and DMDC was the most effective method of reducing quality deterioration in potatoes compared to the control and individual treatments. Furthermore, the combined treatment of E2H, VC, and DMDC could decrease the accumulation of reactive oxygen species (ROS) via improving antioxidant enzyme activities. Meanwhile, energy-metabolism-related enzyme activities and glutamate decarboxylase (GAD) activity were enhanced, while γ-aminobutyric acid transaminase (GABA-T) activity was reduced via the combined treatment of E2H, VC, and DMDC, which contributed to maintaining high energy levels and GABA content in potatoes. These findings suggested that the combined treatment of E2H, VC, and DMDC could protect membrane integrity through enhancing antioxidant capacity, energy levels, and GABA content to maintain quality in fresh-cut potatoes.

Genome-Wide Identification of Calmodulin-Binding Protein 60 Gene Family and the Function of GhCBP60B in Cotton Growth and Development and Abiotic Stress Response

The calmodulin-binding protein 60 (CBP60) family is a gene family unique to plants, and its members play a crucial role in plant defense responses to pathogens and growth and development. Considering that cotton is the primary source of natural cotton textile fiber, the functional study of its CBP60 gene family members is critical. In this research, we successfully identified 162 CBP60 members from the genomes of 21 species. Of these, 72 members were found in four cotton species, divided into four clades. To understand the function of GhCBP60B in cotton in depth, we conducted a detailed analysis of its sequence, structure, cis-acting elements, and expression patterns. Research results show that GhCBP60B is located in the nucleus and plays a crucial role in cotton growth and development and response to salt and drought stress. After using VIGS (virus-induced gene silencing) technology to conduct gene silencing experiments, we found that the plants silenced by GhCBP60B showed dwarf plants and shortened stem nodes, and the expression of related immune genes also changed. In further abiotic stress treatment experiments, we found that GhCBP60B-silenced plants were more sensitive to drought and salt stress, and their POD (peroxidase) activity was also significantly reduced. These results imply the vital role of GhCBP60B in cotton, especially in regulating plant responses to drought and salt stress. This study systematically analyzed CBP60 gene family members through bioinformatics methods and explored in depth the biological function of GhCBP60B in cotton. These research results lay a solid foundation for the future use of the GhCBP60B gene to improve cotton plant type and its drought and salt resistance.

Genome-Wide Identification and Expression Analysis of Rosa roxburghii Autophagy-Related Genes in Response to Top-Rot Disease

Autophagy is a highly conserved process in eukaryotes that degrades and recycles damaged cells in plants and is involved in plant growth, development, senescence, and resistance to external stress. Top-rot disease (TRD) in Rosa roxburghii fruits caused by Colletotrichum fructicola often leads to huge yield losses. However, little information is available about the autophagy underlying the defense response to TRD. Here, we identified a total of 40 R. roxburghii autophagy-related genes (RrATGs), which were highly homologous to Arabidopsis thaliana ATGs. Transcriptomic data show that RrATGs were involved in the development and ripening processes of R. roxburghii fruits. Gene expression patterns in fruits with different degrees of TRD occurrence suggest that several members of the RrATGs family responded to TRD, of which RrATG18e was significantly up-regulated at the initial infection stage of C. fructicola. Furthermore, exogenous calcium (Ca²⁺) significantly promoted the mRNA accumulation of RrATG18e and fruit resistance to TRD, suggesting that this gene might be involved in the calcium-mediated TRD defense response. This study provided a better understanding of R. roxburghii autophagy-related genes and their potential roles in disease resistance.

Effect of CaCl2 Treatment on Enzymatic Browning of Fresh-Cut Luffa (Luffa cylindrica)

Enzymatic browning is a major issue that reduces the commercial value of Luffa cylindrica during storage, processing, and transportation. Our results showed that 1% CaCl2 treatment was optimal for reducing the surface browning of fresh-cut luffa. After storage at 25 °C for four days, the treated luffa had a significantly higher total phenolic (TP) content than the untreated luffa. At the end of the storage period, the calcium treatment showed low malondialdehyde (MDA) and hydrogen peroxide (H2O2) accumulation in the luffa. The treated luffa maintained higher superoxide dismutase (SOD), catalase (CAT), and phenylalanine ammonia lyase (PAL) activities and lower polyphenol oxidase (PPO) activity as compared to the untreated luffa. Furthermore, the genes regulating SOD (e.g., SOD1, SOD2, and SOD3), CAT (e.g., LcCAT1 and CAT2), and PAL (e.g., PAL1 and PAL2) in calcium-treated luffa were upregulated to varying degrees, suggesting that Ca2+ inhibited the browning of fresh-cut tissue by regulating the activities of those enzymes. Ultrastructure images showed that the treated luffa could maintain the relative integrity of the cell membrane and organelles. Therefore, Ca2+ might act as a second messenger to reduce ROS oxidative damage and maintain the cell membrane integrity. This study provides new insights into the breeding of new luffa varieties that are resistant to browning and post-harvest treatments to reduce the browning of luffa tissue.

Effect of calcium treatment on the browning of harvested eggplant fruits and its relation to the metabolisms of reactive oxygen species (ROS) and phenolics

Eggplant is a popular vegetable in Asia; however, it has a short storage life and considerable economic losses have resulted from eggplant browning. Calcium has been reported to play a key role in the postharvest storage of plants. Here, we found that exogenous calcium application could delay eggplant fruit browning and maintain higher storage quality. The increased browning index (BI), relative electrolytic leakage (REL), and water loss were suppressed by calcium treatment during storage. Delayed browning with calcium treatment might result from a higher phenolic level and suppressed the activity of polyphenol oxidase (PPO). Less H2O2 and O2 - but more activated reactive oxygen species (ROS) scavenging enzymes accumulated in calcium-treated fruits than in H2O-treated fruits. Moreover, the nonenzymatic antioxidant, ascorbic acid (AsA), was accumulated more in calcium-treated eggplant fruits. Taken together, our data demonstrated that exogenous calcium application delayed eggplant fruit browning by regulating phenol metabolism and enhancing antioxidant systems.

Effects of CaCl2 Treatment Alleviates Chilling Injury of Loquat Fruit (Eribotrya japonica) by Modulating ROS Homeostasis

The effects of calcium chloride (CaCl₂) treatment on chilling injury (CI), reactive oxygen species (ROS) metabolism, and ascorbate-glutathione (AsA-GSH) cycle in loquat fruit at 1 °C storage for 35 d were investigated. The results indicated that CaCl₂ treatment remarkably suppressed the increase in browning index and firmness as well as the decrease in extractable juice rate. CaCl₂ treatment also decreased the production of superoxide radical (O2•-), hydrogen peroxide (H₂O₂) content, but increased the 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical (OH•) scavenging ability, the activities of superoxide dismutase (SOD), catalase (CAT), and their gene expressions. Moreover, compared to the control loquat fruit, CaCl₂-treated fruit maintained higher contents of AsA, GSH, higher levels of activities of ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR) and expressions of EjAPX, EjGR, EjMDHAR, and EjDHAR, but exhibited lower glutathione disulfide (GSSG) content. These results suggested that CaCl₂ treatment alleviated CI in loquat fruit through enhancing antioxidant enzymes activities and AsA-GSH cycle system to quench ROS.

Transcriptome and metabolomic analysis to reveal the browning spot formation of 'Huangguan' pear

BACKGROUND

Browning spot (BS) disorders seriously affect the appearance quality of 'Huangguan' pear and cause economic losses. Many studies on BS have mainly focused on physiological and biochemical aspects, and the molecular mechanism remains unclear.

RESULTS

In the present study, the structural characteristics of 'Huangguan' pear with BS were observed via scanning electron microscopy (SEM), the water loss and brown spots were evaluated, and transcriptomic and metabolomics analyses were conducted to reveal the molecular mechanism underlying 'Huangguan' pear skin browning disorder. The results showed that the occurrence of BS was accompanied by a decrease in the wax layer and an increase in lignified cells. Genes related to wax biosynthesis were downregulated in BS, resulting in a decrease in the wax layer in BS. Genes related to lignin were upregulated at the transcriptional level, resulting in upregulation of metabolites related to phenylpropanoid biosynthesis. Expression of calcium-related genes were upregulated in BS. Cold-induced genes may represent the key genes that induce the formation of BS. In addition, the results demonstrated that exogenous NaH₂PO₄·2H₂O and ABA treatment could inhibit the incidence of BS during harvest and storage time by increasing wax-related genes and calcium-related genes expression and increasing plant resistance, whereas the transcriptomics results indicated that GA₃ may accelerate the incidence and index of BS.

CONCLUSIONS

The results of this study indicate a molecular mechanism that could explain BS formation and elucidate the effects of different treatments on the incidence and molecular regulation of BS.