Strawberry is one of the most highly consumed fruits worldwide, but is extremely perishable. This study systematically compared the effects of chitosan, sucrose, glucose, and fructose immersion on the physiology and disease development in harvested strawberries. After storage at 15 °C for 9 days, all sugar treatment groups had significantly higher total soluble solids and total anthocyanin content than those of the control group. All sugar treatment groups inhibited malondialdehyde accumulation. At the end of the storage, chitosan, glucose, and fructose maintained higher superoxide dismutase activity and chitosan maintained higher catalase activity. The chitosan and glucose groups had lowest fruit decay index, followed by sucrose and fructose groups. The fruit firmness and luster were better maintained in the glucose group. Furthermore, genes related to sucrose metabolism (e.g., FaSUS1 and FaSUS2), titratable acidity accumulation (e.g., FaMDH1, FaMDH2, FaCS1, and FaCS2), disease resistance (e.g., FaPGIP1, FaWRKY1, and FaWRKY33) and to anabolic jasmonic acid and abscisic acid pathways (e.g., FaJAZ1, FaJAZ2, FaOPR3, FaNCED1, and FaNCED2) were regulated to varying degrees, suggesting that chitosan and glucose participate in plants’ immune signaling networks and regulate disease resistance in fruit through hormone pathways. The findings provide new insights into the physiological regulation of harvested strawberries.

A total of 54 FvbZIP genes were identified from the strawberry genome. These genes were found to be unevenly distributed on seven different chromosomes, and two of the genes had no matching chromosomal localization. FvbZIP genes were divided into 10 subfamilies according to protein sequence, and the structures of these genes were found to be highly conserved. Based on the bioinformatics analysis of FvbZIP genes, the expression of FabZIP genes changed during different stages of its growth and of its infection with gray mold disease. FabZIP46 was substantially upregulated, and its expression remained relatively high. FabZIP46 was cloned from cultivated strawberries by homologous cloning. The results of a transient transgenic assay revealed that the damage to the fruit tissue was markedly alleviated in strawberries overexpressing FabZIP46, with the incidence rate being substantially lower than that in the control group. By contrast, a brief silencing of FabZIP46 had the opposite effect. The results revealed that FabZIP46 played a positive role in the resistance of strawberries to Botrytis cinerea. The study findings provide valuable insights into the role of bZIP transcription factors as well as a theoretical reference for the regulation of resistance to gray mold disease in strawberry fruit.

The ABA receptor pyrabactin resistance 1-like (PYR/PYL) protein family is among the key regulators of plant growth and development, participating in ABA signaling. However, information on this family in strawberry (Fragaria × ananassa), an important fleshy fruit crop worldwide, is limited. In the present work, seven homologs of Arabidopsis PYL were first identified and characterized from Fragaria × ananassa. Furthermore, a comprehensive analysis of the FaPYLs was performed, including their phylogenetic relationships, gene structures, chromosomal locations, and conserved domains. The qRT–PCR analysis showed that FaPYL genes had differential expression patterns between fruit ripening stages, and most of them were transcribed in the SG (small green fruits,) and Wh (white fruits) stages of fruit ripening. Treatment of strawberry fruits with ABA and JA changed the expression of all FaPYLs in a gene-specific manner, depending on the berry ripening stage; at the turning stage, only the expression levels of FaPYL3 and FaPYL4 increased in response to ABA. Promoter analysis showed that most FaPYL genes contain cis-acting elements that respond to stress, light, and phytohormones and are associated with tissue-specific expression. Additionally, FaPYL3 and FaPYL4 were further functionally characterized using transient expression technology. Overexpression of FaPYL3 and FaPYL4 promoted strawberry fruit ripening, which positively regulated FaSnRK2.2 and FaNCED1 transcripts. Our results highlight the great potential of FaPYL genes in breeding genetically modified strawberry varieties with accelerated fruit ripening.