Transformation of plant cells with T-DNA of virulent agrobacteria is one of the 
most extreme triggers of developmental changes in higher plants. For rapid 
growth and development of resulting tumors, specific changes in the gene 
expression profile and metabolic adaptations are required. Increased transport 
and metabolic fluxes are critical preconditions for growth and tumor 
development. A functional genomics approach, using the Affymetrix whole genome 
microarray (approximately 22,800 genes), was applied to measure changes in gene 
expression. The solute pattern of Arabidopsis thaliana tumors and uninfected 
plant tissues was compared with the respective gene expression profile. 
Increased levels of anions, sugars, and amino acids were correlated with changes 
in the gene expression of specific enzymes and solute transporters. The 
expression profile of genes pivotal for energy metabolism, such as those 
involved in photosynthesis, mitochondrial electron transport, and fermentation, 
suggested that tumors produce C and N compounds heterotrophically and gain 
energy mainly anaerobically. Thus, understanding of gene-to-metabolite networks 
in plant tumors promotes the identification of mechanisms that control tumor 
development.