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Pomegranate fruit production and consumption are restricted by appropriate postharvest handling practices. 1–MCP (1–methylcyclopropene) is a natural preservative of fruits and vegetables; however, its effects on the storage of different pomegranate varieties have not been extensively investigated. Herein, the effects of 1.0 μL L−1 1–MCP on postharvest pomegranate fruit of three soft-seed ‘Mollar’, ‘Malisi’, and ‘Tunisan soft seed’ and two semi-soft-seed ‘Moyuruanzi’ and ‘Dongyan’ were investigated over 90 d (days) under low-temperature storage at 4 ± 0.5 °C with a relative humidity of 85–90%. Several indexes of exterior and interior quality were recorded, the sensory quality was evaluated, and the respiration and ethylene production were also determined. The results showed that peel browning was generally more severe in the soft-seed varieties than in the semi-soft-seed varieties. Significantly lighter peel browning presented in the three soft-seed fruits from 45 d after the 1–MCP treatment, with 35%, 19%, and 28% less than those controls at 90 d, correspondingly. However, 1–MCP only significantly decreased peel browning in the semi soft-seed fruits at 60 days. A prominent decrease in weight loss was recorded in all five varieties, with ‘Malisi’ showing the largest and ‘Dongyan’ the smallest difference between the 1–MCP and control treatments. Through the results of color, physiological, and chemical changes, as well as sensory properties, better color and total acceptance were found with higher titratable acids and vitamin C but with decreased anthocyanins in most fruits treated with 1–MCP. In contrast to the control, remarkable suppression of ethylene production peaks in all whole fruits and periodical increase in respiration rates in the soft-seed whole fruits were activated at 30–60 d after storage by the 1–MCP treatment, roughly when peel browning occurred and began increasing. Overall, our findings provided a crucial foundation for extending the application of 1–MCP in postharvest preservation of pomegranates.

Laccase (LAC) is the key enzyme responsible for lignin biosynthesis. Here, 57 PgLACs from pomegranate were identified and distributed on eight chromosomes and one unplaced scaffold. They were divided into six groups containing three typical Cu-oxidase domains. Totally, 51 cis-acting elements in the promoter region of PgLACs are involved in response to ABA, GA, light, stress, etc., indicating diverse functions of PgLACs. The expression profiles of 13 PgLACs during the seed development stage showed that most PgLACs expressed at a higher level earlier than at the later seed development stage in two pomegranate cultivars except PgLAC4. Also, PgLAC1/6/7/16 expressed at a significantly higher level in soft-seed ‘Tunisia’; on the contrary, PgLAC37 and PgLAC50 with a significantly higher expression in hard-seed ‘Taishanhong’. Combined with their distinguishing cis-acting elements, it was concluded that PgLAC1/6/7 may respond to GA via TATC-box and GARE-motif, and PgLAC16 repressed the promotor activity of embryo mid-maturation genes via RY-element so as to contribute to softer seed formation, whereas PgLAC37/50 may participate in seed formation and accelerate seed maturity via ABRE and G-box elements. Collectively, the dramatic gene expressions of PgLAC1/6/7/16/37/50 will provide valuable information to explore the formation of soft- and hard-seed in pomegranate.

Arginine is a natural preservative; however, its effects on the storage of different cultivars of pomegranates have not been investigated extensively. Therefore, the fruit quality of soft-seed Tunisia and hard-seed Yudazi pomegranates was investigated after treatment with arginine at four concentrations during cold storage for 80 days. Pomegranates treated with 1.0 mM arginine exhibited a relatively lower loss of vitamin C, soluble solid, total phenol, and anthocyanin contents in arils, together with a better fruit appearance. Combined with principal component analysis (PCA), the storage life of fruits treated with 1.0 mM arginine showed a higher correlation with antioxidant enzyme activity (e.g., superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT)) during the first 40 days of cold storage, whereas after 40 days of cold storage, storage life was more dependent on the integrity of the cell membrane affected by malondialdehyde (MDA) content, electrolyte leakage (EL), and hydrogen peroxide (H2O2) accumulation. Arginine treatment contributed significantly to the appearance and inner quality of the hard-seed pomegranate cv. Yudazi fruit during cold storage compared to those of soft-seed Tunisia. Taken together, arginine application combined with cold storage enhanced the nutraceutical properties and marketability of pomegranate fruits.

Pomegranate fruit production and consumption are restricted by appropriate postharvest handling practices. 1–MCP (1–methylcyclopropene) is a natural preservative of fruits and vegetables; however, its effects on the storage of different pomegranate varieties have not been extensively investigated. Herein, the effects of 1.0 μL L−1 1–MCP on postharvest pomegranate fruit of three soft-seed 'Mollar', 'Malisi', and 'Tunisan soft seed' and two semi-soft-seed 'Moyuruanzi' and 'Dongyan' were investigated over 90 d (days) under low-temperature storage at 4 ± 0.5 °C with a relative humidity of 85–90%. Several indexes of exterior and interior quality were recorded, the sensory quality was evaluated, and the respiration and ethylene production were also determined. The results showed that peel browning was generally more severe in the soft-seed varieties than in the semi-soft-seed varieties. Significantly lighter peel browning presented in the three soft-seed fruits from 45 d after the 1–MCP treatment, with 35%, 19%, and 28% less than those controls at 90 d, correspondingly. However, 1–MCP only significantly decreased peel browning in the semi soft-seed fruits at 60 days. A prominent decrease in weight loss was recorded in all five varieties, with 'Malisi' showing the largest and 'Dongyan' the smallest difference between the 1–MCP and control treatments. Through the results of color, physiological, and chemical changes, as well as sensory properties, better color and total acceptance were found with higher titratable acids and vitamin C but with decreased anthocyanins in most fruits treated with 1–MCP. In contrast to the control, remarkable suppression of ethylene production peaks in all whole fruits and periodical increase in respiration rates in the soft-seed whole fruits were activated at 30–60 d after storage by the 1–MCP treatment, roughly when peel browning occurred and began increasing. Overall, our findings provided a crucial foundation for extending the application of 1–MCP in postharvest preservation of pomegranates. [ABSTRACT FROM AUTHOR]

Laccase (LAC) is the key enzyme responsible for lignin biosynthesis. Here, 57 PgLACs from pomegranate were identified and distributed on eight chromosomes and one unplaced scaffold. They were divided into six groups containing three typical Cu-oxidase domains. Totally, 51 cis-acting elements in the promoter region of PgLACs are involved in response to ABA, GA, light, stress, etc., indicating diverse functions of PgLACs. The expression profiles of 13 PgLACs during the seed development stage showed that most PgLACs expressed at a higher level earlier than at the later seed development stage in two pomegranate cultivars except PgLAC4. Also, PgLAC1/6/7/16 expressed at a significantly higher level in soft-seed 'Tunisia'; on the contrary, PgLAC37 and PgLAC50 with a significantly higher expression in hard-seed 'Taishanhong'. Combined with their distinguishing cis-acting elements, it was concluded that PgLAC1/6/7 may respond to GA via TATC-box and GARE-motif, and PgLAC16 repressed the promotor activity of embryo mid-maturation genes via RY-element so as to contribute to softer seed formation, whereas PgLAC37/50 may participate in seed formation and accelerate seed maturity via ABRE and G-box elements. Collectively, the dramatic gene expressions of PgLAC1/6/7/16/37/50 will provide valuable information to explore the formation of soft- and hard-seed in pomegranate. [ABSTRACT FROM AUTHOR]

Cold stress limits plant growth, development and yields, and the C-repeat binding factors (CBFs) function in the cold resistance in plants. However, how pomegranate CBF transcription factors respond to cold signal remains unclear. Considering the significantly up-regulated expression of PgCBF3 and PgCBF7 in cold-tolerant Punica granatum 'Yudazi' in comparison with cold-sensitive 'Tunisia' under 4 °C, the present study focused on the two CBF genes. PgCBF3 was localized in the nucleus, while PgCBF7 was localized in the cell membrane, cytoplasm, and nucleus, both owning transcriptional activation activity in yeast. Yeast one-hybrid and dual-luciferase reporter assay further confirmed that PgICE1 could specifically bind to and significantly enhance the activation activity of the promoters of PgCBF3 and PgCBF7. Compared with the wild-type plants, the PgCBF3 and PgCBF7 transgenic Arabidopsis thaliana lines had the higher survival rate after cold treatment; exhibited increased the contents of soluble sugar and proline, while lower electrolyte leakage, malondialdehyde content, and reactive oxygen species production, accompanying with elevated enzyme activity of catalase, peroxidase, and superoxide dismutase; and upregulated the expression of AtCOR15A, AtCOR47, AtRD29A, and AtKIN1. Collectively, PgCBFs were positively regulated by the upstream PgICE1 and mediated the downstream COR genes expression, thereby enhancing freezing tolerance. [ABSTRACT FROM AUTHOR]