Jian-Qiang Yu

Gray mold, caused by Botrytis cinerea, severely threatens strawberry production worldwide, yet the molecular mechanisms underlying strawberry resistance remain poorly understood. Here, we show that the transcription factor ETHYLENE INSENSITIVE 3 (FaEIN3), a strawberry EIN3/EIL homolog, positively regulates strawberry resistance to B. cinerea by directly activating the transcription of the WRKY transcription factor gene FaWRKY40. FaWRKY40 further induces the cytokinin biosynthesis gene FaLOG1 and the jasmonic acid biosynthesis gene FaAOC4, thereby promoting hormone accumulation and enhancing disease resistance. Moreover, the JAMM-family deubiquitinase FaPSMD14 physically interacts with FaEIN3 in the nucleus and stabilizes FaEIN3, thereby strengthening FaEIN3-mediated activation of FaWRKY40. Our findings reveal a previously uncharacterized defense mechanism in which the FaPSMD14–FaEIN3–FaWRKY40 regulatory cascade promotes strawberry resistance to B. cinerea through coordinated activation of the cytokinin and jasmonic acid pathways.

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.

Strawberry (Fragaria × ananassa Duch.) is a small berry characterized by its bright color and sweet-sour flavor. With the global rise in living standards, the strawberry industry has experienced rapid growth, and enhancing the comprehensive quality of the fruit has become a focal point in current strawberry research. Previous studies often concentrated on improving single quality indices, with a notable lack of regulatory factors for enhancing overall strawberry fruit quality. In this study, transgenic strawberries with inhibited FaMYB44.1 expression were developed using instantaneous transformation technology. Further analysis of related quality indices revealed that FaMYB44.1 is a MYB transcription factor that inhibits fruit ripening. TRV-FaMYB44.1 transgenic strawberry fruits exhibited significantly increased anthocyanin content and markedly decreased organic acid levels. DAP-seq analysis demonstrated that FaMYB44.1 binds to multiple promoters, untranslated regions (UTRs), exons, and introns within the genome. The associated target genes are enriched in various primary and secondary metabolic pathways, including carbohydrate metabolism, citric acid cycle (TCA cycle), flavonoid biosynthesis, and flavonoid and flavanol biosynthesis. Motif analysis identified DREME (AAGTA) as the binding motif of the strawberry FaMYB44.1 transcription factor. This research confirms FaMYB44.1's involvement in regulating diverse metabolic processes, contributing to the improvement of overall strawberry fruit quality, and provides a valuable gene target for molecular breeding endeavors.

Salt stress severely affects the growth and yield of apples (Malus domestica Borkh). Although salt‐tolerant genes have been extensively studied, documentation on the role of the ATP‐dependent phosphofructokinase gene MdPFK5 in salt stress is limited. This study conducted an evolutionary tree and three‐dimensional structure analysis of the PFK gene family in Arabidopsis thaliana and MdPFK (MD01G1037400), revealing a close phylogenetic relationship between MdPFK (MD01G1037400) and AtPFK5. Given the similarity in their protein tertiary structures, MdPFK was designated as MdPFK5, suggesting functional similarities with AtPFK5. Further investigation revealed elevated expression levels of MdPFK5 in apple leaves and flowers, particularly showing significant upregulation 120 days after blooming and differential expression beginning at 3 hours of salt stress. Overexpression of MdPFPK5 conferred salt tolerance in both apple calli and transgenic lines of Arabidopsis thaliana. Moreover, NaCl treatment promoted soluble sugar accumulation in apple calli and transgenic lines of Arabidopsis thaliana overexpressing MdPFK5. This study provides new insights into the salt tolerance function of MdPFK5.

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.

Excessive application of nitrate, an essential macronutrient and a signal regulating diverse physiological processes, decreases malate accumulation in apple fruit, but the underlying mechanism remains poorly understood. Here, we show that an apple BTB/TAZ protein MdBT2 is involved in regulating malate accumulation and vacuolar pH in response to nitrate. In vitro and in vivo assays indicate that MdBT2 interacts directly with and ubiquitinates a bHLH transcription factor, MdCIbHLH1, via the ubiquitin/26S proteasome pathway in response to nitrate. This ubiquitination results in the degradation of MdCIbHLH1 protein and reduces the transcription of MdCIbHLH1-targeted genes involved in malate accumulation and vacuolar acidification including MdVHA-A encoding a vacuolar H ⁺ -ATPase gene, and MdVHP1 encoding a vacuolar H ⁺ -pyrophosphatase gene, as well as MdALMT9 encoding a aluminum-activated malate transporter gene. A series of transgenic analyses in apple materials including fruits, plantlets and calli demonstrate that MdBT2 controls nitrate-mediated malate accumulation and vacuolar pH at least partially, if not completely, via regulating the MdCIbHLH1 protein level. Taken together, these findings reveal that MdBT2 regulates the stability of MdCIbHLH1 via ubiquitination in response to nitrate, which in succession transcriptionally reduces the expression of malate-associated genes, thereby controlling malate accumulation and vacuolar acidification in apples under high nitrate supply.

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.