Abstract
Low temperature is a major adverse environment that affects normal plant growth. Previous reports showed that the actin cytoskeleton plays an important role in the plant response to low-temperature stress, but the regulatory mechanism of the actin cytoskeleton in this process is not clear. C-repeat binding factors (CBFs) are the key molecular switches for plants to adapt to cold stress. However, whether CBFs are involved in the regulation of the actin cytoskeleton has not been reported. We found that Arabidopsis actin depolymerizing factor 5 (ADF5), an ADF that evolved F-actin bundling function, was up-regulated at low temperatures. We also demonstrated that CBFs bound to the ADF5 promoter directly in vivo and in vitro. The cold-induced expression of ADF5 was significantly inhibited in the cbfs triple mutant. The freezing resistance of the adf5 knockout mutant was weaker than that of wild type (WT) with or without cold acclimation. After low-temperature treatment, the actin cytoskeleton of WT was relatively stable, but the actin cytoskeletons of adf5, cbfs, and adf5 cbfs were disturbed to varying degrees. Compared to WT, the endocytosis rate of the amphiphilic styryl dye FM4-64 in adf5, cbfs, and adf5 cbfs at low temperature was significantly reduced. In conclusion, CBFs directly combine with the CRT/DRE DNA regulatory element of the ADF5 promoter after low-temperature stress to transcriptionally activate the expression of ADF5; ADF5 further regulates the actin cytoskeleton dynamics to participate in the regulation of plant adaptation to a low-temperature environment.
Highlights
Low temperature is a major plant stress factor that causes plant growth delay, stagnation, and retrogression and reduces grain yield (Dolferus, 2014; Zhang et al, 2019)
We found that C-repeat binding factors (CBFs) directly bound to the CRT/dehydration responsive element (DRE) DNA regulatory element of the actin depolymerizing factor 5 (ADF5) promoter to induce the up-regulation of ADF5 expression and finely regulated actin cytoskeleton dynamics at low temperature and affected the endocytosis rate of the FM4-64-labeled plasma membrane
The results showed that the endocytosis rate of adf5-1, cbfs-1, and adf5 cbfs mutants was faster than wild type (WT), and there was significant differences between adf5-1, adf5 cbfs, and WT, respectively, but there was no significant difference in cbfs-1
Summary
Low temperature is a major plant stress factor that causes plant growth delay, stagnation, and retrogression and reduces grain yield (Dolferus, 2014; Zhang et al, 2019). Plants have created a series of complex mechanisms to adapt to low-temperature stress. Cold acclimation is one of these mechanisms. When plants are exposed to non-freezing low temperatures for a period of time, their tolerance to lower temperatures improves (Thomashow, 1999; Shi et al, 2018). C-repeat binding factors (CBFs) are the key molecular switches in this process (Liu J. et al, 2018). CBF1, CBF2, and CBF3, known as DREB1B, DREB1C, and DREB1A, belong to the AP2/ERF transcription factor family, which recognizes the C-repeat
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