The roles in photosystem I (PSI) assembly of the nucleus-encoded thylakoid protein Y3IP1 who interacts with the plastid-encoded Ycf3 protein that has been well-characterized in plants. However, its function and potential mechanisms in other aspects remain poorly understood. We identified the apple MdY3IP1 gene, which encodes a protein highly homologous to the Arabidopsis Y3IP1 (AtY3IP1). Ectopic expression of MdY3IP1 triggered early-flowering and enhanced salt tolerance in Arabidopsis plants. MdY3IP1 controlled floral transition by accelerating sugar metabolism process in plant cells, thereby influencing the expression of flowering-associated genes. The increase in salt stress tolerance in MdY3IP1-expressing plants correlated with reduced reactive oxygen species (ROS) accumulation, and an increase in lateral root development by regulating both auxin biosynthesis and transport, as followed by enhancement of salt tolerance in Arabidopsis. Overall, these findings provide new evidences for additional functions of Y3IP1-like proteins and their underlying mechanisms of which Y3IP1 confers early-flowering and salt tolerance phenotypes in plants. These observations suggest that plant growth and stress resistance can be affected by the regulation of the MdY3IP1 gene. Further molecular and genetic approaches will accelerate our knowledge of MdY3IP1 functions in PSI complex formation and plants stress resistance, and inform strategies for creating transgenic crop varieties with early maturity and high-resistant to adverse environmental conditions.

Ethylene is a key hormone that regulates the maturation and quality formation of horticultural crops, but its effects on non-respiratory climacteric fruits such as strawberries are not yet clear. In this study, strawberry fruits were treated with exogenous ethephon (ETH) and 1-methylcyclopropene (1-MCP). It was found that ETH treatment increased the soluble solids and anthocyanin content of the fruits, reduced hardness, and decreased organic acid content, while 1-MCP treatment inhibited these processes. Transcriptome analysis revealed that differentially expressed genes (DEGs) were enriched in the starch–sucrose metabolism pathway. qRT-PCR results further showed significant changes in the expression levels of sucrose metabolism genes, confirming the influence of ethylene signals on soluble sugar accumulation during strawberry fruit development. This study elucidates the quality changes and molecular mechanisms of ethylene signal in the development of strawberry fruits, providing some key targets and theoretical support for guiding strawberry cultivation and variety improvement.

The ripening of fleshy fruits is a highly complex process characterized by changes in quality attributes such as sugar, acid, and anthocyanin content. Among these, the levels of major organic acids (citric and malic acids) are crucial determinants of fruit taste quality. However, the mechanisms underlying the biosynthesis and metabolism of organic acids (citric and malic acids) in strawberries—especially those influenced by ethylene signaling—remain inadequately understood. This study elucidates the ethylene-mediated regulation of organic acid (citric and malic acids) metabolism in strawberry fruits through the FaMAP3K–FaERF13–FaKAT module. We identified FaERF13 as a key transcription factor that directly binds to and represses the FaKAT promoter (electrophoretic mobility shift assay, yeast 1-hybrid, luciferase reporter assay), thereby promoting the accumulation of total organic acids. Comparative analysis of red (“Benihoppe”) and white (“Snow Princess”) cultivars revealed that this regulatory mechanism is consistently observed, although post-translational modifications likely explain the acid reduction in ripening “Snow Princess” despite high FaERF13 expression. Protein interaction studies (yeast 2-hybrid, co-immunoprecipitation, bimolecular fluorescence complementation) demonstrated that FaMAP3K physically interacts with FaERF13, forming a signaling cascade that fine-tunes the homeostasis of organic acids (citric and malic acids). Functional validation in strawberry and tobacco systems confirmed that FaMAP3K enhances FaERF13-mediated FaKAT suppression. These findings establish a dual-layer regulatory network in which ethylene coordinates both transcriptional (FaERF13–FaKAT) and post-translational (FaMAP3K–FaERF13) control of acid metabolism during strawberry ripening.