Following this observation we were prompted to search for DE genes involved in GA metabolism and signalling. On the other hand, four genes coding for gibberellin-2-oxidases, which inactivate GAs by introducing a hydroxyl at the 2b position, were all upregulated. In rice, under low GA concentrations, the DELLA transcription factor SLR1 represses the GA responses. When GA level increases, the soluble receptor GID1 binds GA, forming the GID1-GA complex. This interacts with SLR1 and leads to its degradation by the 26S proteasome, thus releasing the repressive state of GA responses. In our data, we found that two genes coding for the nuclear gibberellin receptor GID1 were induced in TYLCSV infected plants, and a transcript coding for the GAI protein, a repressor of GA signalling similar to the rice protein SLR1, was repressed. All the above observations suggest a role for GA in plant-TYLCSV interaction, with an increase in GA levels during infection, 6-Maleimidohexanoic acid N-hydroxysuccinimide ester partially counteracted by the induction of the GA-inactivating enzymes gibberellin-2-oxidases. Recent studies revealed a complex crosstalk between GA, ABA and JA signalling mediating plant growth and response to abiotic and biotic stresses. We found that the GO category response to abscisic acid stimulus was overrepresented among up-regulated genes, and the gene coding for the abscisic acid 8’-hydroxylase, a key enzyme for ABA degradation, was down-regulated. These data suggest an increase of ABA level during TYLCSV infection. Actually, in addition to playing a key role in developmental processes and in response to abiotic stresses, ABA has been shown to be involved in the interaction between RNA viruses and their host plants. ABA level was observed to increase in tomato shoots infected by Tomato spotted wilt virus and in tobacco leaves systemically infected by TMV; interestingly, treatment with exogenous ABA improved resistance to TMV infection in tobacco. A first relation between ABA and geminivirus infection was observed in Arabidopsis plants inoculated with the curtovirus, Beet severe curly top virus. ATHB12 and ATHB7 genes, coding for two transcription factors belonging to the homeodomain-leucine zipper family,6-Maleimidocaproic Acid previously shown to be induced by abscisic acid, were also induced in symptomatic BSCTV-infected tissues. Moreover, ATHB12 expression was correlated with several morphological abnormalities such as leaf curling, stunting, and callus-like structures in infected Arabidopsis plants. As far as we know, no other evidence of the ABA involvement in geminivirus infection was found so far. JA has recently received attention in geminivirus research. Although we do not see overrepresentation of genes involved in JA metabolism or in JA response, changes in expression of some individual JA-related transcripts were observed. Salicylic acid is another hormone with an important role in many plant-pathogen interactions and it is known to activate local and systemic defence responses, particularly against biotrophs. Activation of the SA pathway is a typical plant response to RNA viruses and a similar induction of SA-mediated responses was observed in the Arabidopsis-CabLCV infection. Surprisingly, we found nine transcripts, coding for phenylalanine ammonia lyases, key enzymes in the SA biosynthesis, all down-regulated in TYLCSVinfected tissues, thus suggesting a decrease in SA levels in infected plants. Moreover, only two genes coding for proteins belonging to the SA-mediated signalling pathway were regulated during infection, one induced and the other repressed in infected tissues.