RESUMO
Environmental stresses are the major factors that limit productivity in plants. Here, we report on the function of an uncharacterized gene At1g07050, encoding a CCT domain-containing protein, from Arabidopsis thaliana. At1g07050 expression is highly repressed by oxidative stress. We used metabolomics, biochemical, and genomic approaches to analyse performance of transgenic lines with altered expression of At1g07050 under normal and oxidative stress conditions. At1g07050 overexpressing lines showed increased levels of reactive oxygen species (ROS), whereas knock-out mutants exhibited decreased levels of ROS and higher tolerance to oxidative stress generated in the chloroplast. Our results uncover a role for At1g07050 in cellular redox homeostasis controlling H2 O2 levels, due to changes in enzymes, metabolites, and transcripts related to ROS detoxification. Therefore, we call this gene FITNESS. Additionally, several genes such as ACD6, PCC1, and ICS1 related to salicylic acid signalling and defence were found differentially expressed among the lines. Notably, FITNESS absence significantly improved seed yield suggesting an effective fine-tuning trade-off between reproductive success and defence responses.
Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/farmacologia , Proteínas Nucleares/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Arabidopsis/genética , Arabidopsis/imunologia , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/farmacologia , Clorofila/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Perfilação da Expressão Gênica , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Filogenia , Imunidade Vegetal , Plantas Geneticamente Modificadas , Reação em Cadeia da Polimerase , Prolina/metabolismo , Reprodução , Transdução de SinaisRESUMO
Transcriptional co-activators of the multiprotein bridging factor 1 (MBF1) controls gene expression by connecting transcription factors and the basal transcription machinery. In Arabidopsis thaliana functions of MBF1 genes have been related to stress tolerance and developmental alterations. Endogenous ABA plays a major role in the regulation of Arabidopsis seed dormancy and germination. Seed dormancy and ABA sensitivity are enhanced in ethylene insensitive mutants suggesting that ethylene signal transduction pathway is necessary to fully develop ABA-dependent germination. In this report we showed that a triple knock-down mutant for Arabidopsis MBF1 genes (abc-) has enhanced seed dormancy and displays hypersensitivity to exogenous ABA. In addition, higher ABA contents were detected in abc- seeds after imbibition. These evidences suggest a negative role of MBF1s genes in ABA-dependent inhibition of germination. The participation of MBF1s in ethylene signal transduction pathway is also discussed.
Assuntos
Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/genética , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Germinação/genética , Sementes/metabolismo , Transativadores/genética , Ácido Abscísico/farmacologia , Arabidopsis/efeitos dos fármacos , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Etilenos/metabolismo , Germinação/efeitos dos fármacos , Mutação , Dormência de Plantas/efeitos dos fármacos , Dormência de Plantas/genética , Reguladores de Crescimento de Plantas/metabolismo , Reguladores de Crescimento de Plantas/farmacologia , Sementes/efeitos dos fármacos , Transdução de Sinais , Transativadores/metabolismoRESUMO
Small heat shock proteins (sHSPs) are chaperones that play an important role in stress tolerance. They consist of an alpha-crystallin domain (ACD) flanked by N- and C-terminal regions. However, not all proteins that contain an ACD, hereafter referred to as ACD proteins, are sHSPs because certain ACD proteins are known to have different functions. Furthermore, since not all ACD proteins have been identified yet, current classifications are incomplete. A total of 17 complete plant proteomes were screened for the presence of ACD proteins by HMMER profiling and the identified ACD protein sequences were classified by maximum likelihood phylogeny. Differences among and within groups were analysed, and levels of functional constraint were determined. There are 29 different classes of ACD proteins, eight of which contain classical sHSPs and five likely chaperones. The other classes contain proteins with uncharacterised or poorly characterised functions. N- and C-terminal sequences are conserved within the phylogenetic classes. Phylogenetics suggests a single duplication of the CI sHSP ancestor that occurred prior to the speciation of mono- and dicotyledons. This was followed by a number of more recent duplications that resulted in the presence of many paralogues. The results suggest that N- and C-terminal sequences of sHSPs play a role in class-specific functionality and that non-sHSP ACD proteins have conserved but unexplored functions, which are mainly determined by subsequences other than that of the ACD.
Assuntos
Evolução Molecular , Proteínas de Choque Térmico Pequenas/genética , Família Multigênica , Plantas/genética , alfa-Cristalinas/genética , Sequência de Aminoácidos , Animais , Análise por Conglomerados , Sequência Conservada , Citosol/metabolismo , Humanos , Filogenia , Multimerização Proteica , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Ratos , Triticum/genética , alfa-Cristalinas/químicaRESUMO
Transcriptional co-activators of the multiprotein bridging factor 1 (MBF1) type belong to a small multigenic family that controls gene expression by connecting transcription factors and the basal transcription machinery. In this report, a triple knock-down mutant (abc-) for the Arabidopsis thaliana MBF1 genes AtMBF1a, AtMBF1b and AtMBF1c was generated. The phenotypic characterization using oxidative agents such as hydrogen peroxide and methyl viologen revealed that the abc- mutant was more sensitive to oxidative stress. The triple knock-down mutant, abc- was also sensitive to osmotic stress mediated by high concentrations of sorbitol. Furthermore, the abc- phenotype was partially or completely rescued by AtMBF1c cDNA over-expression (abc- +c) depending on physiological and developmental conditions. AtMBF1s regulate the expression of ABR1, which is a member of the ethylene-response factor family and acts as ABA repressor. Thus, we conclude that AtMBF1 gene family may function as a regulatory component of the cross-talk node between ethylene, ABA and stress signal pathways. Furthermore, higher levels of a HSP70 mRNA and an immunoreactive HSP70 protein were detected in the abc- mutant. The participation of MBF1c as a possible negative regulator of HSP genes was discussed.