![]() ![]() A total of 13 LxLxLxL EAR motifs were identified, including 4 LxLxLxL motifs that overlap with DLNx(x)P ( Table S7). Through an analysis of the LxLxL motifs and the generation of the LxLxL sequence logo with 12 amino acids before and after the EAR motif ( Figure 1A), it was discovered that there are several extended LxLxL motifs among the EAR repressors identified in this study. Interestingly, 22 (15.5%) of the EAR motifs contained overlapping motif sequences-either multiple overlapping LxLxL motifs (14) or LxLxL motifs overlapping with the DLNx(x)P motifs (12). The 119 functionally characterized EAR repressors contain a total of 143 EAR motif instances ( Table S1) of which 45 (31.5%) contain DLNx(x)P type of EAR motif ( Table 1, Tables S2–S5), and 110 (76.9%) contain a conserved consensus sequence of LxLxL ( Tables S6–S8). Consensus Sequence and the Localization of the EAR Motif 2.1. By classifying these proteins in this way, we were able to compare EAR motif-containing proteins that have similar functions across distinct species. As such, in order to effectively analyze the EAR motif-containing proteins across an array of plant species, we separated the proteins into 7 categories according to known biological function (discussed in Section 3: Molecular functions of EAR motif-containing proteins). As EAR motif-containing proteins have been characterized in a wide array of plants, this allows for comparisons and analyses to be conducted over a broader dataset of plant species. In this review, we focus on the similarities and differences between the fully characterized EAR repressors and leverage this information to provide insights into how the EAR motifs play an important role in negative regulation of gene expression in plants. Though more than 20,000 EAR motif-containing proteins exist in different plant species, 119 EAR motif-containing proteins have been functionally characterized to-date and the role of EAR motif in these candidates has been confirmed ( Table 1). The EAR motif was first identified 20 years ago in plants and its role in negative gene regulation has been well documented. The ethylene-responsive element binding factor-associated amphiphilic repression (EAR) motif-mediated transcriptional repression has emerged as one of the principal mechanisms for active repression of gene expression in plants. The latter is facilitated by either inhibiting the components of the basal transcriptional machinery or by recruiting chromatin modifiers which can modify chromatin structure and prevent transcriptional activators from binding to the target cis-elements. Active transcriptional repressors generally associate with target genes in one of two ways: by directly binding to their promoter elements through a DNA binding domain or indirectly by interacting with DNA-bound proteins, conferring repression. Plants employ a wide repertoire of transcriptional repression mechanisms that are generally orchestrated by a complex and coordinated network of active or passive repressors, corepressors, components of basal transcriptional machinery and chromatin modifiers. In the past decade, remarkable progress has been made in elucidating the molecular nature and functions of transcriptional repression complexes. Transcriptional repression is a key regulatory mechanism essential for the modulation of gene expression during plant development, stress responses, and hormone signaling. This review aims to fill the knowledge gap and provide insights into the role that the EAR motif plays in negative gene regulation, and provoke further research on other protein motifs specific to repressors. Positive gene regulation and transcriptional activation are studied extensively, but there remains much more to be discovered about negative gene regulation and the role it plays in plant development, health, and reproduction. ![]() Through an extensive literature review, we identified 119 genes belonging to 23 different plant species that contain an EAR motif and function as negative regulators of gene expression in various biological processes, including plant growth and morphology, metabolism and homeostasis, abiotic stress response, biotic stress response, hormonal pathways and signalling, fertility, and ripening. Despite its small size (5 to 6 amino acids), the EAR motif is primarily involved in the negative regulation of developmental, physiological and metabolic functions in response to abiotic and biotic stresses. ![]() It is the most predominant form of active transcriptional repression motif identified so far in plants. The ethylene-responsive element binding factor-associated amphiphilic repression (EAR) motif, defined by the consensus sequence patterns LxLxL or DLNx(x)P, is found in a diverse range of plant species. ![]()
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