RESUMEN
Plants have two endosymbiotic organelles originated from two bacterial ancestors. The transition from an independent bacterium to a successful organelle would have required extensive rewiring of biochemical networks for its integration with archaeal host. Here, using Arabidopsis as a model system, we show that plant D-aminoacyl-tRNA deacylase 1 (DTD1), of bacterial origin, is detrimental to organellar protein synthesis owing to its changed tRNA recognition code. Plants survive this conflict by spatially restricting the conflicted DTD1 to the cytosol. In addition, plants have targeted archaeal DTD2 to both the organelles as it is compatible with their translation machinery due to its strict D-chiral specificity and lack of tRNA determinants. Intriguingly, plants have confined bacterial-derived DTD1 to work in archaeal-derived cytosolic compartment whereas archaeal DTD2 is targeted to bacterial-derived organelles. Overall, the study provides a remarkable example of the criticality of optimization of biochemical networks for survival and evolution of plant mitochondria and chloroplast.
Asunto(s)
Arabidopsis , Orgánulos , Orgánulos/metabolismo , Mitocondrias/metabolismo , Aminoacil-ARN de Transferencia/metabolismo , Cloroplastos/metabolismo , ARN de Transferencia/metabolismo , Arabidopsis/genéticaRESUMEN
We have investigated the mechanism of action of SWITCH1/DYAD (SWI1), an important regulator of plant meiosis in Arabidopsis that is required for meiotic chromosome organization including maintenance of sister chromatid cohesion. The central portion of SWI1 contains a domain of unknown function that shows strong conservation between SWI1 and its orthologs in maize and rice and is also found in paralogs including MALE MEIOCYTE DEATH 1 (MMD1). In order to examine the role of this domain we performed domain swap experiments into SWI1 in a swi1 mutant background. Domain swap analysis revealed functional conservation of the central domain between SWI1 and its orthologs but not with the domain from MMD1 suggesting that the domain plays an important role in SWI1 function that has been conserved in orthologs and diverged in paralogs in plant evolution. Analysis of expression of the non-complementing MMD1 domain swap SWI1(DSMMD1)::GFP transgenic lines revealed an altered pattern of expression that suggests a role for SWI1 in commitment to female meiocyte differentiation and meiosis. The results suggest that SWI1 may also play a developmental role as an identity determinant in the female germ cell lineage in addition to its known role in meiotic chromosome organization.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citología , Proteínas de Ciclo Celular/metabolismo , Diferenciación Celular , Expresión Génica Ectópica , Meiosis , Proteínas Nucleares/metabolismo , Óvulo Vegetal/citología , Dominios Proteicos , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/genética , Linaje de la Célula , Regulación de la Expresión Génica de las Plantas , Proteínas Nucleares/química , Proteínas Nucleares/genética , Oryza/genética , Dominios Proteicos/genética , Alineación de Secuencia , Zea mays/genéticaRESUMEN
Aldehydes, being an integral part of carbon metabolism, energy generation, and signalling pathways, are ingrained in plant physiology. Land plants have developed intricate metabolic pathways which involve production of reactive aldehydes and its detoxification to survive harsh terrestrial environments. Here, we show that physiologically produced aldehydes, i.e., formaldehyde and methylglyoxal in addition to acetaldehyde, generate adducts with aminoacyl-tRNAs, a substrate for protein synthesis. Plants are unique in possessing two distinct chiral proofreading systems, D-aminoacyl-tRNA deacylase1 (DTD1) and DTD2, of bacterial and archaeal origins, respectively. Extensive biochemical analysis revealed that only archaeal DTD2 can remove the stable D-aminoacyl adducts on tRNA thereby shielding archaea and plants from these system-generated aldehydes. Using Arabidopsis as a model system, we have shown that the loss of DTD2 gene renders plants susceptible to these toxic aldehydes as they generate stable alkyl modification on D-aminoacyl-tRNAs, which are recycled only by DTD2. Bioinformatic analysis identifies the expansion of aldehyde metabolising repertoire in land plant ancestors which strongly correlates with the recruitment of archaeal DTD2. Finally, we demonstrate that the overexpression of DTD2 offers better protection against aldehydes than in wild type Arabidopsis highlighting its role as a multi-aldehyde detoxifier that can be explored as a transgenic crop development strategy.
Asunto(s)
Aldehídos , Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Aminoacil-ARN de Transferencia/metabolismo , Bacterias/genética , Archaea/genética , Archaea/metabolismo , ARN de TransferenciaRESUMEN
The serotonin1A (5-HT1A) receptor is an important neurotransmitter receptor that belongs to the G protein-coupled receptor (GPCR) family. It is implicated in a variety of cognitive and behavioral functions and serves as an important drug target for neuropsychiatric disorders such as anxiety and depression. Previous work from our laboratory has demonstrated that membrane cholesterol plays an important role in the function of the serotonin1A receptor. Our earlier results highlighted several structural features of cholesterol essential for receptor function. In order to explore the importance of the hydroxyl group of cholesterol in the function of the serotonin1A receptor, we utilized cholesterol oxidase to oxidize the hydroxyl group of cholesterol to keto group. Our results show that the oxidation of the hydroxyl group of cholesterol in live cells resulted in enhancement of agonist binding and G-protein coupling to the receptor with no appreciable change in overall membrane order. These results extend our understanding of the structural requirements of cholesterol for receptor function.