PlWRKY47 Coordinates With Cytosolic Glyceraldehyde-3-Phosphate Dehydrogenase 2 Gene to Improve Thermotolerance Through Inhibiting Reactive Oxygen Species Generation in Herbaceous Peony.

Although WRKY transcription factors play crucial roles in plant responses to high-temperature stress, little is known about Group IIb WRKY family members. Here, we identified the WRKY-IIb protein PlWRKY47 from herbaceous peony (Paeonia lactiflora Pall.), which functioned as a nuclear-localized transcriptional activator. The expression level of PlWRKY47 was positively correlated with high-temperature tolerance. Silencing of PlWRKY47 in P. lactiflora resulted in the decreased tolerance to high-temperature stress by accumulating reactive oxygen species (ROS). Overexpression of PlWRKY47 improved plant high-temperature tolerance through decreasing ROS accumulation. Moreover, PlWRKY47 directly bound to the promoter of cytosolic glyceraldehyde-3-phosphate dehydrogenase 2 (PlGAPC2) gene and activated its transcription. PlGAPC2 was also positively regulated high-temperature tolerance in P. lactiflora by increasing NAD+ content to inhibit ROS generation. Additionally, PlWRKY47 physically interacted with itself to form a homodimer, and PlWRKY47 could also interact with one Group IIb WRKY family member PlWRKY72 to form a heterodimer, they all promoted PlWRKY47 to bind to and activate PlGAPC2. These data support that the PlWRKY47-PlWRKY47 homodimer and PlWRKY72-PlWRKY47 heterodimer can directly activate PlGAPC2 expression to improve high-temperature tolerance by inhibiting ROS generation in P. lactiflora. These results will provide important insights into the plant high-temperature stress response by WRKY-IIb transcription factors.

Herbaceous peony AP2/ERF transcription factor binds the promoter of the tryptophan decarboxylase gene to enhance high-temperature stress tolerance.

Global warming has multifarious adverse effects on plant growth and productivity. Nonetheless, the effects of endogenous phytomelatonin on the high-temperature resistance of plants and the underlying genetic mechanisms remain unclear. Here, herbaceous peony (Paeonia lactiflora Pall.) tryptophan decarboxylase (TDC) gene involved in phytomelatonin biosynthesis was shown to respond to high-temperature stress at the transcriptional level, and its transcript level was positively correlated with phytomelatonin production. Moreover, overexpression of PlTDC enhanced phytomelatonin production and high-temperature stress tolerance in transgenic tobacco, while silencing PlTDC expression decreased these parameters in P. lactiflora. In addition, a 2402 bp promoter fragment of PlTDC was isolated, and DNA pull-down assay revealed that one APETALA2/ethylene-responsive element-binding factor (AP2/ERF) transcription factor, PlTOE3, could specifically activate the PlTDC promoter, which was further verified by yeast one-hybrid assay and luciferase reporter assay. PlTOE3 was a nucleus-localized protein, and its transcript level responded to high-temperature stress. Additionally, transgenic tobacco overexpressing PlTOE3 showed enhanced phytomelatonin production and high-temperature stress tolerance, while silencing PlTDC expression obtained the opposite results. These results illustrated that PlTOE3 bound the PlTDC promoter to enhance high-temperature stress tolerance by increasing phytomelatonin production in P. lactiflora.

Multi-walled carbon nanotubes prevent high temperature-induced damage by activating the ascorbate-glutathione cycle in Paeonia ostii T. Hong et J. X. Zhang.

Multi-walled carbon nanotubes (MWCNTs) are considered important nanomaterials with rapidly growing applications. They are inevitably released into the environment, which has attracted considerable attention for their potential threats to ecosystems. In this study, Paeonia ostii T. Hong et J. X. Zhang was exposed to MWCNTs at different concentrations under high temperature. The results showed that high temperature-induced P. ostii damage was prevented by MWCNTs, and 200 mg/L was the most effective concentration. First, MWCNTs prevented increases in reactive oxygen species, relative electrical conductivity and free proline content, and reduced decreases in SPAD, chlorophyll and carotenoid contents. Moreover, the ascorbate-glutathione (ASA-GSH) cycle was activated in response to the MWCNTs treatments, whereas the superoxide dismutase and catalase activities were inhibited. And the MWCNTs treatments also resulted in higher photosynthesis and more intact anatomical structures. Furthermore, the metabolome also confirmed that the ASA-GSH cycle played a critical role in P. ostii high-temperature tolerance, and other biological processes also responded to the MWCNTs treatments. Additionally, the genes involved in the P. ostii ASA-GSH cycle were highly expressed in response to the MWCNTs treatments. These results elucidated the beneficial role of MWCNTs in P. ostii growth under high temperature.

R2R3-MYB Transcription Factor PlMYB108 Confers Drought Tolerance in Herbaceous Peony (Paeonia lactiflora Pall.).

The MYB transcription factor (TF) is crucial for plant growth, development, and response to abiotic stress, but it is rarely reported in the herbaceous peony (Paeonia lactiflora Pall.). Here, an MYB TF gene was isolated, and based on our prior mRNA data from P. lactiflora samples, it was treated with drought stress (DS). Its complete cDNA structure was 1314 bp, which encoded 291 amino acids (aa). Furthermore, using sequence alignment analysis, we demonstrated that PlMYB108 was an R2R3-MYB TF. We also revealed that PlMYB108 was primarily localized in the nucleus. Its levels rose during DS, and it was positively correlated with drought tolerance (DT) in P. lactiflora. In addition, when PlMYB108 was overexpressed in tobacco plants, the flavonoid content, antioxidant enzyme activities, and photosynthesis were markedly elevated. Hence, the transgenic plants had stronger DT with a higher leaf water content and lower H2O2 accumulation compared to the wild-type (WT) plants. Based on these results, PlMYB108 is a vital gene that serves to increase flavonoid accumulation, reactive oxygen species (ROS), scavenging capacity, and photosynthesis to confer DT. The results would provide a genetic resource for molecular breeding to enhance plant DT.

WRKY Transcription Factor Response to High-Temperature Stress.

Plant growth and development are closely related to the environment, and high-temperature stress is an important environmental factor that affects these processes. WRKY transcription factors (TFs) play important roles in plant responses to high-temperature stress. WRKY TFs can bind to the W-box cis-acting elements of target gene promoters, thereby regulating the expression of multiple types of target genes and participating in multiple signaling pathways in plants. A number of studies have shown the important biological functions and working mechanisms of WRKY TFs in plant responses to high temperature. However, there are few reviews that summarize the research progress on this topic. To fully understand the role of WRKY TFs in the response to high temperature, this paper reviews the structure and regulatory mechanism of WRKY TFs, as well as the related signaling pathways that regulate plant growth under high-temperature stress, which have been described in recent years, and this paper provides references for the further exploration of the molecular mechanisms underlying plant tolerance to high temperature.