Delaying Broccoli Floret Yellowing by Phytosulfokine α Application During Cold Storage

Phytomelatonin: From Intracellular Signaling to Global Horticulture Market

Melatonin (N-acetyl-5-methoxytryptamine), a well-known mammalian hormone, has been having a great relevance in the Plant World in recent years. Many of its physiological actions in plants are leading to possible features of agronomic interest, especially those related to improvements in tolerance to stressors and in the postharvest life of fruits and vegetables. Thus, through the exogenous application of melatonin or by modifying the endogenous biosynthesis of phytomelatonin, some change can be made in the functional levels of melatonin in tissues and their responses. Also, acting in the respective phytomelatonin biosynthesis enzymes, regulating the expression of tryptophan decarboxylase (TDC), tryptamine 5-hydroxylase (T5H), serotonin N-acetyltransferase (SNAT), N-acetylserotonin O-methyltransferase (ASMT), and caffeic acid O-methyltransferase (COMT), and recently the possible action of deacetylases on some intermediates offers promising opportunities for improving fruits and vegetables in postharvest and its marketability. Other regulators/effectors such as different transcription factors, protein kinases, phosphatases, miRNAs, protein-protein interactions, and some gasotransmitters such as nitric oxide or hydrogen sulfide were also considered in an exhaustive vision. Other interesting aspects such as the role of phytomelatonin in autophagic responses, the posttranslational reprogramming by protein-phosphorylation, ubiquitylation, SUMOylation, PARylation, persulfidation, and nitrosylation described in the phytomelatonin-mediated responses were also discussed, including the relationship of phytomelatonin and several plant hormones, for chilling injury and fungal decay alleviating. The current data about the phytomelatonin receptor in plants (CAND2/PMTR1), the effect of UV-B light and cold storage on the postharvest damage are presented and discussed. All this on the focus of a possible new action in the preservation of the quality of fruits and vegetables.

Sulfated peptides and their receptors: Key regulators of plant development and stress adaptation

Four distinct types of sulfated peptides have been identified in Arabidopsis thaliana. These peptides play crucial roles in regulating plant development and stress adaptation. Recent studies have revealed that Xanthomonas and Meloidogyne can secrete plant-like sulfated peptides, exploiting the plant sulfated peptide signaling pathway to suppress plant immunity. Over the past three decades, receptors for these four types of sulfated peptides have been identified, all of which belong to the leucine-rich repeat receptor-like protein kinase subfamily. A number of regulatory proteins have been demonstrated to play important roles in their corresponding signal transduction pathways. In this review, we comprehensively summarize the discoveries of sulfated peptides and their receptors, mainly in Arabidopsis thaliana. We also discuss their known biological functions in plant development and stress adaptation. Finally, we put forward a number of questions for reference in future studies.

H2S-Generating Cytosolic L-Cysteine Desulfhydrase and Mitochondrial D-Cysteine Desulfhydrase from Sweet Pepper (Capsicum annuum L.) Are Regulated During Fruit Ripening and by Nitric Oxide

Aims: Pepper fruit is a horticultural product worldwide consumed that has great nutritional and economic relevance. Besides the phenotypical changes that undergo pepper fruit during ripening, there are many associated modifications at transcriptomic, proteomic, biochemical, and metabolic levels. Nitric oxide (NO) and hydrogen sulfide (H2S) are recognized signal molecules that can exert regulatory functions in diverse plant processes. This study aims at analyzing the interrelationship between NO and H2S during fruit ripening. Results: Our data indicate that the H2S-generating cytosolic L-cysteine desulfhydrase (LCD) and the mitochondrial D-cysteine desulfhydrase (DCD) activities are downregulated during ripening but this effect was reverted after NO treatment of fruits. Innovation and Conclusion: Using as a model the non-climacteric pepper fruits at different ripening stages and under an NO-enriched atmosphere, the activity of the H2S-generating LCD and DCD was analyzed. LCD and DCD activities were downregulated during ripening, but this effect was reverted after NO treatment of fruits. The analysis of LCD activity by non-denaturing polyacrylamide gel electrophoresis (PAGE) allowed identifying three isozymes designated CaLCD I to CaLCD III, which were differentially modulated by NO and strictly dependent on pyridoxal 5'-phosphate (PLP). In vitro analyses of green fruit samples in the presence of different compounds including NO donors, peroxynitrite (ONOO-), and reducing agents such as reduced glutathione (GSH) and L-cysteine (L-Cys) triggered an almost 100% inhibition of CaLCD II and CaLCD III. This redox adaptation process of both enzymes could be cataloged as a hormesis phenomenon. The protein tyrosine (Tyr) nitration (an NO-promoted post-translational modification) of the recombinant LCD was corroborated by immunoblot and by mass spectrometry (MS) analyses. Among the 11 Tyr residues present in this enzyme, MS of the recombinant LCD enabled us to identify that Tyr82 and Tyr254 were nitrated by ONOO-, this occurring near the active center on the enzyme, where His237 and Lys260 together with the cofactor PLP are involved. These data support the relationship between NO and H2S during pepper fruit ripening, since LCD and DCD are regulated by NO during this physiological event, and this could also be extrapolated to other plant species.

Maintaining the quality of postharvest broccoli by inhibiting ethylene accumulation using diacetyl

Broccoli (Brassica oleracea L. var. Italic) is rich in nutrition. However, it is susceptible to yellowing after harvest, leading to nutritional and economic losses. In this study, diacetyl, a natural food additive compound, was selected to inhibit the yellowing of broccoli florets and maintain the nutrient quality during storage time. It was found that 20 μl L^-1 diacetyl treatment for 12 h could significantly delay the yellowing and decrease the weight loss and lignin content of broccoli florets. Meanwhile, diacetyl could maintain higher contents of chlorophyll, vitamin C and flavonoids and suppress the transcript levels of chlorophyll degradation-related genes in broccoli florets. Moreover, accumulations of reactive oxygen species (ROS) were inhibited by diacetyl treatment. Under diacetyl treatment, the generation of ethylene was prevented by inhibiting the activities and related-gene expressions of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase. Based on our findings, exogenous diacetyl could be employed as a novel bioactive molecule for retarding the yellowing and maintaining the quality of postharvest broccoli.

The chromosome-scale genome provides insights into pigmentation in Acer rubrum

Acer rubrum L. is one of the most prevalent ornamental species of the genus Acer, due to its straight and tall stems and beautiful leaf colors. For this study, the Oxford Nanopore platform and Hi-C technology were employed to obtain a chromosome-scale genome for A. rubrum. The genome size of A. rubrum was 1.69 Gb with an N50 of 549.44 Kb, and a total of 39 pseudochromosomes were generated with a 99.61% genome. The A. rubrum genome was predicted to have 64644 genes, of which 97.34% were functionally annotated. Genome annotation identified 67.14% as the transposable element (TE) repeat sequence, with long terminal repeats (LTR) being the richest (55.68%). Genome evolution analysis indicated that A. rubrum diverged from A. yangbiense ∼6.34 million years ago. We identified 13 genes related to pigment synthesis in A. rubrum leaves, where the expressions of four ArF3'H genes were consistent with the synthesis of cyanidin (a key pigment) in red leaves. Correlation analysis verified that the pigmentation of A. rubrum leaves was under the coordinated regulation of non-structural carbohydrates and hormones. The genomic sequence of A. rubrum will facilitate genomic breeding research for this species, while providing the valuable utilization of Aceraceae resources.

Phytosulfokine α (PSKα) delays senescence and reinforces SUMO1/SUMO E3 ligase SIZ1 signaling pathway in cut rose flowers (Rosa hybrida cv. Angelina)

Roses are widely used as cut flowers worldwide. Petal senescence confines the decorative quality of cut rose flowers, an impressively considerable economic loss. Herein, we investigated the SUMO1/SUMO E3 ligase SIZ1 signaling pathway during bud opening, and petal senescence of cut rose flowers. Our results exhibited that the higher expression of SUMO1 and SUMO E3 ligase SIZ1 during bud opening was accompanied by lower endogenous H2O2 accumulation arising from higher expression and activities of SOD, CAT, APX, and GR, promoting proline accumulation by increasing P5CS expression and activity and enhancing GABA accumulation by increasing GAD expression and activity. In harvested flowers, lower expressions of SUMO1 and SUMO E3 ligase SIZ1 during petal senescence were associated with higher endogenous H2O2 accumulation due to lower expression and activities of SOD, CAT, APX, and GR. Therefore, promoting the activity of the GABA shunt pathway as realized by higher expression and activities of GABA-T and SSADH accompanied by increasing OAT expression and activity for sufficiently supply proline in rose flowers during petal senescence might serve as an endogenous antisenescence mechanism for slowing down petals senescence by avoiding endogenous H2O2 accumulation. Following phytosulfokine α (PSKα) application, postponing petal senescence in cut rose flowers could be ascribed to higher expression of SUMO1 and SUMO E3 ligase SIZ1 accompanied by higher expression and activities of SOD, CAT, APX, and GR, higher activity of GABA shunt pathway as realized by higher expression and activities of GAD, GABA-T, and SSADH, higher expression and activities of P5CS and OAT for supplying proline and higher expression of HSP70 and HSP90. Therefore, our results highlight the potential of the PSKα as a promising antisenescence signaling peptide in the floriculture industry for postponing senescence and extending the vase life of cut rose flowers.

Gum Arabic Edible Coating Reduces Postharvest Decay and Alleviates Nutritional Quality Deterioration of Ponkan Fruit During Cold Storage

The storability recession during storage limits the postharvest storage life of Ponkan (Citrus reticulata Blanco cv. Ponkan) fruit and its nutritional value, which potentially lead to huge losses. To develop an effective technique to reduce Ponkan fruit postharvest decay and to maintain the nutritional quality, the preservation effect of 9, 12, and 15% postharvest gum arabic (GA) coatings on Ponkan fruit was investigated. The 12 and 15% GA coatings effectively reduced fruit decay as well as weight loss, retained higher total soluble solids (TSS) content, suppressed titratable acidity (TA) degradation, and postponed the rise in ripening index (RI). Moreover, the 12% GA-coated fruit exhibited a lower respiration rate, electrical conductivity, and malondialdehyde (MDA) accumulation than the uncoated (control) fruit. The 12% GA coating treatment decreased the loss of ascorbic acid (AsA), total phenols, and total flavonoids and maintained higher amounts of non-enzymatic antioxidants. Furthermore, the 12% GA coating treatment increased antioxidant enzymes' activities as well as delayed the reduction of total antioxidant capacity (TAC). These results suggest that, with the cold storage increasing time, the 12% GA-coated fruit exhibited better postharvest storability and higher nutritional quality than the control fruit. The GA coating treatment could be used as a commercial wax to improve postharvest storability, extend its storage life, and maintain the nutritional value of Ponkan fruit up to 120 days of cold storage.