Postharvest 24-epibrassinolide treatment improves chilling resistance of peach fruit via PpHDT1 modulating brassinosteroid metabolism

Effects of exogenous EBR on the physiology of cold resistance and the expression of the VcCBF3 gene in blueberries during low-temperature stress

The northern highbush blueberry variety 'Duke' was used as the test material, and different concentrations of 2,4-Epibrassinolide (EBR) (0, 0.2, 0.4, 0.6, and 0.8 mg·L-1) were applied during the bud expansion stage, with a second application administered at one-day intervals following the first. Samples were collected at the bud, flower, and fruit stages and subsequently treated with artificial low temperatures (2°C) after sampling. The effects of various concentrations of exogenous EBR on the physiological indices of cold resistance and the expression of the cold resistance gene VcCBF3 in blueberry buds, flowers, and young fruits were investigated through comprehensive evaluation and correlation analysis. The objective was to identify the optimal concentration of EBR to enhance the cold resistance of blueberries. The results indicate that: (1) Under low temperature stress, the contents of soluble sugar, soluble protein and proline increased, along with the activities of superoxide dismutase, peroxidase, and catalase. The expression of the VcCBF3 gene expression and the ascorbate-glutathione cycling system were up-regulated, and with the increase of EBR concentration, the expression of the VcCBF3 gene initially rose and then declined. The content of malondialdehyde and the production rate of superoxide anion radicals decreased, and with the increase of EBR concentration, the content of malondialdehyde first decreased and then increased. (2) Overall low temperature resistance, flowers > buds > young fruits. (3) Appropriate concentrations of exogenous EBR can effectively mitigate freezing damage in blueberries caused by low temperatures. A comprehensive evaluation and correlation analysis of each cold tolerance index and the expression of the VcCBF3 gene revealed that a treatment concentration of 0.4 mg·L-1 had the most significant mitigating effect among the sprayed EBR concentrations of 0, 0.2, 0.4, 0.6, and 0.8 mg·L-1.

Effects of exogenous brassinosteroids on the starch structure, physicochemical properties and digestibility of wheat under high-temperature stress at the early grain-filling stage

The starch synthesis of wheat was seriously affected by high temperature stress, which affected its yield and quality. At the same time, plant hormones are often used to regulate crop production and mitigate environmental stress in times of adversity. However, whether Brassinosteroids (BRs) can alleviate the adverse effects of high-temperature stress on wheat starch and its internal mechanism are still unclear. Therefore, a two-year field experiment was carried out from 2020 to 2022 to explore the effects of exogenous BRs spraying on the wheat yield, morphological structure and physicochemical properties of starch under high-temperature stress at the early grain-filling stage. The results showed that exogenous spraying of BRs under high-temperature stress increased the activity of key enzymes involved in starch synthesis, the contents of amylose (25.34 %) and amylopectin (11.57 %) were increased on average in two years, and ultimately increased the yield. On the other hand, BRs increased the number of B-type (49.90 %) and C-type starch granules (23.19 %), decreased the number of A-type starch granules (6.38 %) under high-temperature stress, and reduced the chain length of B1 (5.04 %) and B2 (4.88 %) chains of amylopectin. Moreover, BRs decreased crystallinity (25.40 %), gelatinization enthalpy (4.76 %) and 1047/1022 cm-1 (1.25 %), thereby improving the cooking quality of the starch. Through further analysis of the rheological properties and digestibility of starch, BRs improved the processing quality of starch and increased the content of resistant starch (RS, 15.77 %), which provided insights for the processing and utilization of food. In summary, under high-temperature stress, exogenous BRs increased wheat yield and improved starch quality. We recommend BRs as an effective management measure to mitigate high-temperature stress to cope with future climate change.

Roles of Nitric Oxide and Brassinosteroid in Improving Fruit Quality during Postharvest: Potential Regulators?

Most postharvest fruits are highly perishable, which directly impairs fruit taste and causes an economic loss of fresh products. Thus, it is necessary to find effective techniques to alleviate this issue. Recently, nitric oxide (NO) and brassinosteroid (BR) have been developed as postharvest alternatives to improve fruit quality. This work mainly reviews the recent processes of NO and BR in improving fruit quality during postharvest. Exogenous NO or BR treatments delayed fruit senescence, enhanced disease resistance, and alleviated chilling injury in postharvest fruit, and potential physiological and biochemical mechanisms mainly include (1) enhancing antioxidant and defense ability, (2) affecting ethylene biosynthesis, (3) regulating sugar and energy metabolism, (4) mediating plant hormone signaling, and (5) regulating protein S-nitrosylation and DNA methylation. This review concludes the functions and mechanisms of NO and BR in improving postharvest fruit quality. Additionally, a specific finding is the possible crosstalk of applications of NO and BR during postharvest fruit storage, which provides new insights into the applicability of NO and BR for delaying fruit senescence, enhancing disease resistances of fruit, and alleviating chilling injury in postharvest fruit.