Complex spatial responses to cucumber mosaic virus infection in susceptible Cucurbita pepo cotyledons

Cucumber mosaic virus infection of its susceptible host Cucurbita pepo resu lts in a program of biochemical changes after virus infection. Applying a s patial analysis to expanding infected lesions, we investigated the relation ship between the changes in enzyme activity and gene expression. Patterns o f altered expression were seen that could not be detected by RNA gel blot a nalysis. For all the host genes studied, there was a downregulation (shutof f) of expression within the lesion. In addition, two distinct types of upre gulation were observed. The expression of heat shock protein 70 (HSP70) and NADP(+)-dependent melic enzyme (NADP-ME) showed induction in apparently un infected cells ahead of the infection. This response was more localized tha n the upregulation exhibited by catalase expression, which occurred through out the uninfected regions of the tissue. The experiments showed that virus infection induced immediate and subsequent changes in gene expression by t he host and that the infection has the potential to give advance signaling of the imminent infection.