Referencia

Plant Cell 25: 4183-4194.

Autores

Pablo Pulido, Gabriela Toledo-Ortiz, Michael A. Phillips, Louwrance P. Wright, y Manuel Rodríguez-Concepción.

Resumen

Plastids provide plants with metabolic pathways that are unique among eukaryotes, including the methylerythritol 4-phosphate pathway for the production of isoprenoids essential for photosynthesis and plant growth. Here, we show that the first enzyme of the pathway, deoxyxylulose 5-phosphate synthase (DXS), interacts with the J-protein J20 in Arabidopsis thaliana. J-proteins typically act as adaptors that provide substrate specificity to heat shock protein 70 (Hsp70), a molecular chaperone. Immunoprecipitation experiments showed that J20 and DXS are found together in vivo and confirmed the presence of Hsp70 chaperones in DXS complexes. Mutants defective in J20 activity accumulated significantly increased levels of DXS protein (but no transcripts) and displayed reduced levels of DXS enzyme activity, indicating that loss of J20 function causes posttranscriptional accumulation of DXS in an inactive form. Furthermore, J20 promotes degradation of DXS following a heat shock. Together, our data indicate that J20 might identify unfolded or misfolded (damaged) forms of DXS and target them to the Hsp70 system for proper folding under normal conditions or degradation upon stress.

Descripción

DXS es el primer enzima de la ruta de biosíntesis de isoprenoides chloroplastídicos. En este trabajo describimos como la cochaperona J20 interacciona específicamente con DXS facilitando su correcto plegamiento por la chaperona molecular Hsp70. DXS se acumula de manera inactiva en el mutante para J20 mientras que la sobreexpresión de J20-GFP provoca una disminución de los niveles de DXS. En conjunto, nuestros datos indican que el sistema J20/Hsp70 participa tanto en el plegamiento como en la degradación de DXS inactiva.

grupo

REFERENCIA DEL GRUPO INVESTIGADOR

Nuestro grupo forma parte del programa de Metabolismo e Ingeniería Metabólica del CRAG, Barcelona (www.cragenomica.es). Su interés principal es entender como los cloroplastos de las células vegetales regulan la biosíntesis de isoprenoides, que son metabolitos esenciales para la fotosíntesis y el desarrollo de la planta. Mediante abordajes de genética, bioquímica, y biología molecular, en los últimos años hemos descubierto varios mecanismos post-transcripcionales que permiten a los cloroplastos controlar finamente los niveles y la actividad de enzimas clave de la biosíntesis de isoprenoides. Nuestro trabajo también abarca la regulación transcripcional de genes biosintéticos en plantas y el estudio de enzimas alternativos en sistemas bacterianos.

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