A genome approach to mitochondrial-nuclear communication in Arabidopsis

Mitochondria depend on the nuclear genome to encode the vast majority of th eir proteins; in turn they control the expression of certain nuclear genes to maintain proper functioning. In this work, Arabidopsis leaves were emplo yed as a model to study nuclear gene expression in response to inhibition o f the mitochondrial electron transport by antimycin A. Microarrays containi ng 11 514 Arabidopsis expressed sequence tags supplied through the Arabidop sis Functional Genomics Consortium (AFGC) were used. Transcript levels of 5 79 nuclear genes were increased greater than or equal to 2-fold, and the le vels of 584 nuclear genes were decreased greater than or equal to 2-fold af ter antimycin A treatment. While functions of a large number of the gene pr oducts are unknown, others are involved in diverse metabolic activities suc h as phosphorylation, transcription, and energy metabolism. Data from micro array experiments were repeatable and were confirmed by northern hybridizat ion for specific test genes. It was found through cluster analysis that pla nt cells show significant common response to chemical inhibition of mitocho ndrial function, aluminum stress, cadmium stress, hydrogen peroxide and vir us infection. The results imply that these stresses may act on mitochondria and the responses are in part mediated by mitochondrial-nuclear communicat ion. Most nuclear-encoded respiratory genes involved in the TCA cycle, elec tron transport and ATP synthesis did not respond to signals from the inhibi ted mitochondria, while genes for cytochrome c and alternative oxidase were induced. The result indicates that these two genes may be targets in the t ranscriptional regulation of the two respiratory pathways. (C) 2001 Edition s scientifiques et medicales Elsevier SAS.