Defense Responses and Metabolic Changes Involving Phenylpropanoid Pathway and PR Genes in Squash ( L.) following Infection.

The current study focuses on the effects of (CMV) infection on phytochemical changes and pathogenesis- and phenylpropanoid pathway-associated gene activities in squash ( L.) plants during a time course of 2 to 12 days post inoculation (dpi). The identity of the CMV isolate was confirmed by DAS-ELISA, TEM, and coat protein gene sequence. The CMV infection initially boosts and then suppresses transcript levels of the defense-related genes , and during the investigated time course compared to controls. The expression profile during the time-course study indicated that early, transient induction of occurs during CMV infection, while CMV induced the expression of in systemically infected squash tissues at all time points and suppressed the expression of and at 8-12 dpi. transcript levels fluctuated between up- and down-regulation, but by 12 dpi, expression reached its peak. The HPLC and GC-MS analyses of CMV-infected squash extracts revealed that different phenolic, flavonoid, and fatty acid compounds could be induced or suppressed upon CMV infection. In particular, CMV could suppress the synthesis of most phenolic compounds, specifically chlorogenic acid, possibly leading to the virus's rapid spread.