RESUMO
Asymmetric cell divisions are essential to generate different cellular lineages. In plants, asymmetric cell divisions regulate the correct formation of the embryo, stomatal cells, apical and root meristems, and lateral roots. Current knowledge of regulation of asymmetric cell divisions suggests that, in addition to the function of key transcription factor networks, epigenetic mechanisms play crucial roles. Therefore, we highlight the importance of epigenetic regulation and chromatin dynamics for integration of signals and specification of cells that undergo asymmetric cell divisions, as well as for cell maintenance and cell fate establishment of both progenitor and daughter cells. We also discuss the polarization and segregation of cell components to ensure correct epigenetic memory or resetting of epigenetic marks during asymmetric cell divisions.
Assuntos
Divisão Celular Assimétrica , Epigênese Genética , Diferenciação Celular , Linhagem da Célula , Desenvolvimento Vegetal/genéticaRESUMO
The MADS transcription factors (TF) are an ancient eukaryotic protein family. In plants, the family is divided into two main lineages. Here, we demonstrate that DNA binding in both lineages absolutely requires a short amino acid sequence C-terminal to the MADS domain (M domain) called the Intervening domain (I domain) that was previously defined only in type II lineage MADS. Structural elucidation of the MI domains from the floral regulator, SEPALLATA3 (SEP3), shows a conserved fold with the I domain acting to stabilise the M domain. Using the floral organ identity MADS TFs, SEP3, APETALA1 (AP1) and AGAMOUS (AG), domain swapping demonstrate that the I domain alters genome-wide DNA-binding specificity and dimerisation specificity. Introducing AG carrying the I domain of AP1 in the Arabidopsis ap1 mutant resulted in strong complementation and restoration of first and second whorl organs. Taken together, these data demonstrate that the I domain acts as an integral part of the DNA-binding domain and significantly contributes to the functional identity of the MADS TF.
Assuntos
Proteínas de Ligação a DNA/química , Proteínas de Homeodomínio/química , Fatores de Transcrição/química , Proteína AGAMOUS de Arabidopsis/química , Proteína AGAMOUS de Arabidopsis/genética , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Ligação a DNA/metabolismo , Flores , Regulação da Expressão Gênica de Plantas , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Proteínas de Domínio MADS/metabolismo , Fenótipo , Domínios e Motivos de Interação entre Proteínas , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
During plant development, morphogenetic processes rely on the activity of meristems. Meristem homeostasis depends on a complex regulatory network constituted by different factors and hormone signaling that regulate gene expression to coordinate the correct balance between cell proliferation and differentiation. ULTRAPETALA1, a transcriptional regulatory protein described as an Arabidopsis Trithorax group factor, has been characterized as a regulator of the shoot and floral meristems activity. Here, we highlight the role of ULTRAPETALA1 in root stem cell niche maintenance. We found that ULTRAPETALA1 is required to regulate both the quiescent center cell division rate and auxin signaling at the root tip. Furthermore, ULTRAPETALA1 regulates columella stem cell differentiation. These roles are independent of the ARABIDOPSIS TRITHORAX1, suggesting a different mechanism by which ULTRAPETALA1 can act in the root apical meristem of Arabidopsis. This work introduces a new component of the regulatory network needed for the root stem cell niche maintenance.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citologia , Arabidopsis/metabolismo , Raízes de Plantas/citologia , Nicho de Células-Tronco , Células-Tronco/citologia , Fatores de Transcrição/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Ciclo Celular , Divisão Celular , Regulação da Expressão Gênica de Plantas , Histona-Lisina N-Metiltransferase , Ácidos Indolacéticos/metabolismo , Meristema/citologia , Meristema/genética , Raízes de Plantas/genética , Transdução de Sinais , Nicho de Células-Tronco/genética , Células-Tronco/metabolismo , Fatores de Transcrição/genéticaRESUMO
Current advances indicate that epigenetic mechanisms play important roles in the regulatory networks involved in plant developmental responses to environmental conditions. Hence, understanding the role of such components becomes crucial to understanding the mechanisms underlying the plasticity and variability of plant traits, and thus the ecology and evolution of plant development. We now know that important components of phenotypic variation may result from heritable and reversible epigenetic mechanisms without genetic alterations. The epigenetic factors Polycomb group (PcG) and Trithorax group (TrxG) are involved in developmental processes that respond to environmental signals, playing important roles in plant plasticity. In this review, we discuss current knowledge of TrxG and PcG functions in different developmental processes in response to internal and environmental cues and we also integrate the emerging evidence concerning their function in plant plasticity. Many such plastic responses rely on meristematic cell behavior, including stem cell niche maintenance, cellular reprogramming, flowering and dormancy as well as stress memory. This information will help to determine how to integrate the role of epigenetic regulation into models of gene regulatory networks, which have mostly included transcriptional interactions underlying various aspects of plant development and its plastic response to environmental conditions.