RESUMO
Land plants evolved from charophytic algae, among which Charophyceae possess the most complex body plans. We present the genome of Chara braunii; comparison of the genome to those of land plants identified evolutionary novelties for plant terrestrialization and land plant heritage genes. C. braunii employs unique xylan synthases for cell wall biosynthesis, a phragmoplast (cell separation) mechanism similar to that of land plants, and many phytohormones. C. braunii plastids are controlled via land-plant-like retrograde signaling, and transcriptional regulation is more elaborate than in other algae. The morphological complexity of this organism may result from expanded gene families, with three cases of particular note: genes effecting tolerance to reactive oxygen species (ROS), LysM receptor-like kinases, and transcription factors (TFs). Transcriptomic analysis of sexual reproductive structures reveals intricate control by TFs, activity of the ROS gene network, and the ancestral use of plant-like storage and stress protection proteins in the zygote.
Assuntos
Chara/genética , Genoma de Planta , Evolução Biológica , Parede Celular/metabolismo , Chara/crescimento & desenvolvimento , Embriófitas/genética , Redes Reguladoras de Genes , Pentosiltransferases/genética , Reguladores de Crescimento de Plantas/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , TranscriptomaRESUMO
Auxin coordinates plant development largely via hierarchical control of gene expression. During the past decades, the study of early auxin genes paired with the power of Arabidopsis genetics have unraveled key nuclear components and molecular interactions that perceive the hormone and activate primary response genes. Recent research in the realm of structural biology allowed unprecedented insight into: (i) the recognition of auxin-responsive DNA elements by auxin transcription factors; (ii) the inactivation of those auxin response factors by early auxin-inducible repressors; and (iii) the activation of target genes by auxin-triggered repressor degradation. The biophysical studies reviewed here provide an impetus for elucidating the molecular determinants of the intricate interactions between core components of the nuclear auxin response module.
Assuntos
Ácidos Indolacéticos/metabolismo , Modelos Moleculares , Proteínas Nucleares/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Plantas/genética , Transdução de Sinais , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Proteínas Nucleares/química , Proteínas Nucleares/genética , Desenvolvimento Vegetal , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Domínios Proteicos , Fatores de Transcrição/química , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Ubiquitin-mediated protein degradation is a common feature in diverse plant cell signaling pathways; however, the factors that control the dynamics of regulated protein turnover are largely unknown. One of the best-characterized families of E3 ubiquitin ligases facilitates ubiquitination of auxin (aux)/indole-3-acetic acid (IAA) repressor proteins in the presence of auxin. Rates of auxin-induced degradation vary widely within the Aux/IAA family, and sequences outside of the characterized degron (the minimum region required for auxin-induced degradation) can accelerate or decelerate degradation. We have used synthetic auxin degradation assays in yeast (Saccharomyces cerevisiae) and in plants to characterize motifs flanking the degron that contribute to tuning the dynamics of Aux/IAA degradation. The presence of these rate motifs is conserved in phylogenetically distant members of the Arabidopsis (Arabidopsis thaliana) Aux/IAA family, as well as in their putative Brassica rapa orthologs. We found that rate motifs can act by enhancing interaction between repressors and the E3, but that this is not the only mechanism of action. Phenotypes of transgenic plants expressing a deletion in a rate motif in IAA28 resembled plants expressing degron mutations, underscoring the functional relevance of Aux/IAA degradation dynamics in regulating auxin responses.