RESUMEN
Repression of embryonic traits during the seed-to-seedling phase transition requires the inactivation of master transcription factors associated with embryogenesis. How the timing of such inactivation is controlled is unclear. Here, we report on a novel transcriptional co-repressor, Arabidopsis thaliana SDR4L, that forms a feedback inhibition loop with the master transcription factors LEC1 and ABI3 to repress embryonic traits post-imbibition. LEC1 and ABI3 regulate their own expression by inducing AtSDR4L during mid to late embryogenesis. AtSDR4L binds to sites upstream of LEC1 and ABI4, and these transcripts are upregulated in Atsdr4l seedlings. Atsdr4l seedlings phenocopy a LEC1 overexpressor. The embryonic traits of Atsdr4l can be partially rescued by impairing LEC1 or ABI3. The penetrance and expressivity of the Atsdr4l phenotypes depend on both developmental and external cues, demonstrating the importance of AtSDR4L in seedling establishment under suboptimal conditions.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Latencia en las Plantas/genética , Proteínas Co-Represoras/metabolismo , Regulación de la Expresión Génica de las Plantas/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Plantones/genética , Plantones/metabolismo , Semillas/metabolismoRESUMEN
The vegetative phase transition is a prerequisite for flowering in angiosperm plants. Mulberry miR156 has been confirmed to be a crucial factor in the vegetative phase transition in Arabidopsis thaliana. The over-expression of miR156 in transgenic Populus × canadensis dramatically prolongs the juvenile phase. Here, we find that the expression of mno-miR156 decreases with age in all tissues in mulberry, which led us to study the hierarchical action of miR156 in mulberry. Utilizing degradome sequencing and dual-luciferase reporter assays, nine MnSPLs were shown to be directly regulated by miR156. The results of yeast one-hybrid and dual-luciferase reporter assays also revealed that six MnSPLs could recognize the promoter sequences of mno-miR172 and activate its expression. Our results demonstrate that mno-miR156 performs its role by repressing MnSPL/mno-miR172 pathway expression in mulberry. This work uncovered a miR156/SPLs/miR172 regulation pathway in the development of mulberry and fills a gap in our knowledge about the molecular mechanism of vegetative phase transition in perennial woody plants.
Asunto(s)
Envejecimiento/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , MicroARNs/metabolismo , Morus/metabolismo , Proteínas de Plantas/metabolismo , Envejecimiento/genética , Arabidopsis/genética , Biología Computacional , Regulación del Desarrollo de la Expresión Génica/genética , Regulación de la Expresión Génica de las Plantas/genética , Hydrastis/genética , Hydrastis/metabolismo , MicroARNs/genética , Morus/genética , Hojas de la Planta/genética , Hojas de la Planta/metabolismo , Proteínas de Plantas/genética , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Plantas Modificadas Genéticamente , Populus/genética , Populus/metabolismo , Regiones Promotoras Genéticas , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Regulación hacia ArribaRESUMEN
Correct timing of developmental phase transitions is critical for the survival and fitness of plants. Developmental phase transitions in plants are partially promoted by controlling relevant genes into active or repressive status. Polycomb Repressive Complex1 (PRC1) and PRC2, originally identified in Drosophila, are essential in initiating and/or maintaining genes in repressive status to mediate developmental phase transitions. Our review summarizes mechanisms in which the embryo-to-seedling transition, the juvenile-to-adult transition, and vegetative-to-reproductive transition in plants are mediated by PRC1 and PRC2, and suggests that PRC1 could act either before or after PRC2, or that they could function independently of each other. Details of the exact components of PRC1 and PRC2 in each developmental phase transitions and how they are recruited or removed will need to be addressed in the future.
Asunto(s)
Proteínas de Plantas/metabolismo , Plantas/embriología , Complejo Represivo Polycomb 1/metabolismo , Complejo Represivo Polycomb 2/metabolismo , Plantones/embriología , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Proteínas de Plantas/genética , Plantas/genética , Plantas/metabolismo , Complejo Represivo Polycomb 1/genética , Complejo Represivo Polycomb 2/genética , Plantones/genética , Plantones/metabolismoRESUMEN
In this study, we investigated the regulatory function of miR396 in the phase transition in Arabidopsis thaliana. Using AtMIR396a/b knockout mutants generated through clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9)-directed genome editing, we showed that miR396 negatively regulates the leaf size and vegetative phase transition, and the first leaf with abaxial trichomes appeared earlier in the mir396ab double mutant than in the wild type (WT) and was significantly delayed in miR396 overexpression lines. Moreover, mir396ab exhibited early flowering, whereas 35S:MIR396a/b and cib4-1 delayed flowering, and the flowering time was negatively correlated with FT gene expression. Furthermore, in arp6 and pie1 mutants, which are deficient in the ATP-dependent chromatin remodeling complex (SWR1-C), miR396 expression was significantly repressed. Compared with the WT, reduced H2A.Z deposit and stronger relative nucleosome occupancy in the promoter region of MIR396a was found in the arp6 mutant, indicating that SWR1-C contributes to the transcriptional activation of MIR396a via nucleosome dynamics. In addition, miR396 displayed specific spatio-temporal expression patterns in the leaf, which was altered in arp6 and pie1, and therefore affected the transcript levels of CIB4 and FT in these mutants. We propose that miR396 is not only a marker of cell differentiation, but also an age signal for leaf development and phase change. Meanwhile, SWR1-C-mediated epigenetic regulation contributes to the age-dependent enhancement of miR396 expression and differential miR396 accumulation among leaves.
Asunto(s)
Arabidopsis/genética , Epigénesis Genética , Regulación de la Expresión Génica de las Plantas , MicroARNs/genética , ARN de Planta/genética , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , MicroARNs/metabolismo , Hojas de la Planta/genética , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , ARN de Planta/metabolismo , Activación TranscripcionalRESUMEN
Polycomb group (PcG) protein-mediated gene silencing is a major regulatory mechanism in higher eukaryotes that affects gene expression at the transcriptional level. Here, we report that two conserved homologous PcG proteins, RING1A and RING1B (RING1A/B), are required for global H2A monoubiquitination (H2Aub) in Arabidopsis. The mutation of RING1A/B increased the expression of members of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) gene family and caused an early vegetative phase transition. The early vegetative phase transition observed in ring1a ring1b double mutant plants was dependent on an SPL family gene, and the H2Aub status of the chromatin at SPL locus was dependent on RING1A/B. Moreover, mutation in RING1A/B affected the miRNA156a-mediated vegetative phase transition, and RING1A/B and the AGO7-miR390-TAS3 pathway were found to additively regulate this transition in Arabidopsis. Together, our results demonstrate that RING1A/B regulates the vegetative phase transition in Arabidopsis through the repression of SPL family genes.