Abstract
A sudden cooling in the early spring or late autumn negatively impacts the plant growth and development. Although a number of studies have characterized the role of the transcription factors (TFs) of plant R2R3-myeloblastosis (R2R3-MYB) in response to biotic and abiotic stress, plant growth, and primary and specific metabolisms, much less is known about their role in Rosa multiflora under chilling stress. In the present study, RmMYB108, which encodes a nuclear-localized R2R3-MYB TF with a self-activation activity, was identified based on the earlier published RNA-seq data of R. multiflora plants exposed to short-term low-temperature stress and also on the results of prediction of the gene function referring Arabidopsis. The RmMYB108 gene was induced by stress due to chilling, salt, and drought and was expressed in higher levels in the roots than in the leaves. The heterologous expression of RmMYB108 in Arabidopsis thaliana significantly enhanced the tolerance of transgenic plants to freezing, water deficit, and high salinity, enabling higher survival and growth rates, earlier flowering and silique formation, and better seed quantity and quality compared with the wild-type (WT) plants. When exposed to a continuous low-temperature stress at 4°C, transgenic Arabidopsis lines–overexpressing RmMYB108 showed higher activities of superoxide dismutase and peroxidase, lower relative conductivity, and lower malondialdehyde content than the WT. Moreover, the initial fluorescence (Fo) and maximum photosynthetic efficiency of photosystem II (Fv/Fm) changed more dramatically in the WT than in transgenic plants. Furthermore, the expression levels of cold-related genes involved in the ICE1 (Inducer of CBF expression 1)-CBFs (C-repeat binding factors)-CORs (Cold regulated genes) cascade were higher in the overexpression lines than in the WT. These results suggest that RmMYB108 was positively involved in the tolerance responses when R. multiflora was exposed to challenges against cold, freeze, salt, or drought and improved the cold tolerance of transgenic Arabidopsis by reducing plant damage and promoting plant growth.
Highlights
Freezing temperatures induce cellular dehydration and limit the plant growth by inhibiting water uptake
The analysis of R. multiflora RNA-seq data (SRA accession no.: PRJNA698412) revealed many differentially expressed genes, which encoded transcription factors (TFs) involved in metabolism, transcription, transport, and signal transduction in response to cold stress
Some genes belonging to the APETALA2/ethylene-responsive factor (AP2/ERF), MYB, and NAC families were expressed in higher levels at both 4◦C (CT1) and −20◦C (CT2) than at 25◦C (CK); the specific functions of most of these genes are unknown
Summary
Freezing temperatures induce cellular dehydration and limit the plant growth by inhibiting water uptake. The transcriptomic analysis of R. multiflora leaves exposed to different temperatures (25, 4, and –20◦C) revealed that genes encoding APETALA2/ethylene-responsive factor (AP2/ERF), myeloblastosis (MYB), basic helix-loop-helix (bHLH), zinc finger protein (ZFP), NAC [NAM (NO APICAL MERISTEM), ATAF (Arabidopsis ACTIVATION FACTOR) and CUC (CUPSHAPED COTYLEDON)] and WRKY transcription factors (TFs) actively participate in the response to cold treatment (Zhang et al, 2016). MYB TFs form one of the largest TF families, which are characterized by 1–4 incomplete conserved repeat (R)-containing DNA-binding domain located near the N-terminus (Klempnauer et al, 1982). The R2R3-MYB TFs form the largest clade and participate in the plant growth, especially in cell differentiation, development of floral organ, specific metabolisms, and response to environmental stress (Albert et al, 2014; Li et al, 2019; Liu et al, 2021)
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