The WRKY gene family is a plant-specific transcription factor (TF) group, playing important roles in many different response pathways of diverse abiotic stresses (drought, saline, alkali, temperature, and ultraviolet radiation, and so forth). In recent years, many studies have explored the role and mechanism of WRKY family members from model plants to agricultural crops and other species. Abiotic stress adversely affects the growth and development of plants. Thus, a review of WRKY with stress responses is important to increase our understanding of abiotic stress responses in plants. Here, we summarize the structural characteristics and regulatory mechanism of WRKY transcription factors and their responses to abiotic stress. We also discuss current issues and future perspectives of WRKY transcription factor research.

Ginkgo biloba is an economically valuable tree, as a variety of flavonoid compounds are produced by the leaves of its seedlings. Although soil salinity is a serious threat to agricultural productivity worldwide, the effect of salt stress on G. biloba seedlings remains unclear. In this study, we found that under high NaCl concentrations (200 and 300 mmol/L), seedling growth was inhibited and the water content, chlorophyll, and peroxidase (POD) enzyme activity were significantly decreased in the leaves, whereas the soluble protein and proline levels increased significantly. However, at low NaCl concentrations (50 and 100 mmol/L), the seedlings grew normally because of the regulation of catalase (CAT) and POD enzyme activities. To elucidate the molecular mechanisms behind G. biloba salt tolerance, we examined the transcriptome of G. biloba seedlings treated with 100 mmol/L NaCl. Twelve differentially expressed genes (DEGs) were found to be involved in ion osmotic potential signal transduction and amplification, including two ABA signaling genes, five CDPK/CIPK genes, and five mitogen-activated protein kinase (MAPK) signaling genes. We also found that NAC transcription factors may be involved in the salt stress response; these included positive regulators (Gb_12203, Gb_27819, Gb_37720, and Gb_41540) and negative regulators (Gb_32549, Gb_35048, and Gb_37444). Importantly, treatment with 100 mmol/L NaCl can significantly improve flavonoid and flavonol glycoside biosynthesis. Simultaneously, the expression of flavonoid biosynthesis-related genes, including PAL (Gb_10949, Gb_21115) and FLS (Gb_00285, Gb_14024, and Gb_14029), was significantly upregulated. Based on these results, we reveal that G. biloba seedlings can tolerate low-level soil salinity stress through the regulation of different kinds of genes and transcriptome factors, especially flavonoid biosynthesis, which is improved to respond to environmental stress.

Ginkgo biloba (ginkgo) leaves have medicinal value due to their high levels of secondary metabolites, such as flavonoids. We found that the flavonoid content in ginkgo leaves increases significantly at high altitudes (Qinghai-Tibet Plateau). Considering that high UV-B radiation is among the key environmental characteristics of the Qinghai-Tibet Plateau, we carried out simulated UV-B treatments on ginkgo seedlings and found that the flavonoid content of the leaves increased significantly following the treatments. Combined with results from our previous studies, we determined that the transcription factor GbHY5 may play a key role in responses to UV-B radiation. Overexpression of GbHY5 significantly promoted the accumulation of flavonoids in both ginkgo callus and Arabidopsis thaliana. Furthermore, yeast two-hybrid and real-time quantitative PCR showed that GbHY5 promoted the expression of GbMYB1 by interacting with GbMYB1 protein. Overexpression of GbMYB1 in ginkgo callus and A. thaliana also significantly promoted flavonoid biosynthesis. GbFLS encodes a key enzyme in flavonoid biosynthesis, and its promoter has binding elements of GbHY5 and GbMYB1. A dual-luciferase reporter assay indicated that while GbHY5 and GbMYB1 activated the expression of GbFLS individually, their co-expression achieved greater activation. Our analyses reveal the molecular mechanisms by which the UV-B-induced GbHY5-GbMYB1-GbFLS module promotes flavonoid biosynthesis in ginkgo, and they provide insight into the use of UV-B radiation to enhance the flavonoid content of ginkgo leaves.

Bud dormancy and release are essential phenomena that greatly assist in adapting to adverse growing conditions and promoting the holistic growth and development of perennial plants. The dormancy and release process of buds in temperate perennial trees involves complex interactions between physiological and biochemical processes influenced by various environmental factors, representing a meticulously orchestrated life cycle. In this review, we summarize the role of phytohormones and their crosstalk in the establishment and release of bud dormancy. External environmental factors, such as light and temperature, play a crucial role in regulating bud germination. We also highlight the mechanisms of how light and temperature are involved in the regulation of bud dormancy by modulating phytohormones. Moreover, the role of nutrient factors, including sugar, in regulating bud dormancy is also discussed. This review provides a foundation for enhancing our understanding of plant growth and development patterns, fostering agricultural production, and exploring plant adaptive responses to adversity.

Horticultural plants contain various secondary metabolites (SMs), including flavonoids, terpenoids, and alkaloids. These compounds play a critical role in plant growth, helping the plants adapt to different types of stress and providing numerous health benefits to humans. Advances in detection methods, such as liquid phase mass spectrometry and spatial metabolomics, have enabled the identification and characterization of a growing variety of SMs and their unique functions in horticultural plants. Recent studies have investigated the effects of SMs on horticultural plants under different biotic and abiotic stresses. This article offers a detailed review of the functions of key representative SMs in horticultural plants, focusing on their responses to biotic and abiotic stresses and their impact on human health. Furthermore, we explore the potential of using these compounds to improve the resistance of horticultural plants through future breeding efforts.