Opposing control by transcription factors MYB61 and MYB3 Increases Freezing Tolerance by relieving C-repeat Binding Factor suppression

Abstract

ORCID IDs: 0000-0003-0210-9408 (Z.Z.); 0000-0002-6839-3272 (X.H.); 0000-0001-5113-7750 (J.W.); 0000-0002-5098-8681 (J.D.).Cold acclimation is an important process by which plants respond to low temperature and enhance their winter hardiness. C-REPEAT BINDING FACTOR1 (CBF1), CBF2, and CBF3 genes were shown previously to participate in cold acclimation in Medicago truncatula. In addition, MtCBF4 is transcriptionally induced by salt, drought, and cold stresses. We show here that MtCBF4, shown previously to enhance drought and salt tolerance, also positively regulates cold acclimation and freezing tolerance. To identify molecular factors acting upstream and downstream of the MtCBF4 transcription factor (TF) in cold responses, we first identified genes that are differentially regulated upon MtCBF4 overexpression using RNAseq Digital Gene Expression Profiling. Among these, we showed that MtCBF4 directly activates the transcription of the COLD ACCLIMATION SPECIFIC15 (MtCAS15) gene. To gain insights into how MtCBF4 is transcriptionally regulated in response to cold, an R2R3-MYB TF, MtMYB3, was identified based on a yeast one-hybrid screen as binding directly to MYB cis-elements in the MtCBF4 promoter, leading to the inhibition of MtCBF4 expression. In addition, another MYB TF, MtMYB61, identified as an interactor of MtMYB3, can relieve the inhibitory effect of MtMYB3 on MtCBF4 transcription. This study, therefore, supports a model describing how MtCBF4 is regulated by antagonistic MtMYB3/MtMYB61 TFs, leading to the up-regulation of downstream targets such as MtCAS15 acting in cold acclimation in M. truncatula.

Medicago falcata MfSTMIR, an E3 ligase of endoplasmic reticulum‐associated degradation, is involved in salt stress response

“…Many abiotic stresses, including salt and drought stress, disrupt protein folding and assembly, resulting in cellular damage. Cells activate the transcription response to overcome stress (Zhang et al ., ; Wang et al ., ). A unique pathway called UPR is activated to protect the ER from being damaged by misfolded or unfolded proteins (Liu et al ., , ).…”

BES1 hinders ABSCISIC ACID INSENSITIVE5 and promotes seed germination in Arabidopsis

“…The BES1-GFP fusion proteins are indicated by asterisks. The transient Luc expression assay was performed as previously described (Zhang et al, 2016). The c. 1 kb promoter region of EM6 was amplified and cloned into the pCAMBIA1381Z vector using the BamHI and SalI sites to generate the reporter construct Pro EM6 :Luc.…”

Identification of tissue-specific and cold-responsive lncRNAs in Medicago truncatula by high-throughput RNA sequencing

“…Medicago truncatula is an annual forage crop [32] and has become a prominent model for legume genomics [33][34][35]. Given that M. truncatula is closely phylogenetically related to the common legume forage alfalfa (Medicago sativa), it is a valuable material to study molecular physiology of environmental stress in legume plants [36][37][38]. Alfalfa is a freezing tolerant legume species with great ability to cold acclimate, and capable of accumulating Cold-Acclimation-Specific (CAS) proteins during cold acclimation [36,39,40].…”

“…Alfalfa is a freezing tolerant legume species with great ability to cold acclimate, and capable of accumulating Cold-Acclimation-Specific (CAS) proteins during cold acclimation [36,39,40]. The CASs are homologous to COR genes that are cis-regulated by CBF/DREB1 factors [36,38]. Similar to other plant species grown in temperate zones, M. truncatula plants have cold-acclimation traits [36,41].…”