Figure 7.

FvMAPK3 accelerates the degradation of FvCHS1 at low temperature. A, Immunoblot analysis of increasing FvCHS1 protein levels along with strawberry fruit ripening. W, white fruit; T, turning fruit; R, red fruit. FvCHS1 was detected with an anti-FvCHS1 antibody. Anti-actin was used as loading control. B, FvCHS1 protein levels in turning fruits and young leaves of EV-OE, FvMAPK3-OE, EV-cr, and FvMAPK3-cr plants. C, FvCHS1 protein levels diminish in white FvMAPK3-OE fruits compared to EV fruits and are more pronounced after treatment at 4°C for 30 min. D, Cell-free degradation assay of recombinant His-FvCHS1. Recombinant His-FvCHS1 protein was incubated with total proteins extracted from EV-OE or FvMAPK3-OE fruits at 37°C with 50 µM MG132 or DMSO only (carrier control). His-FvCHS1 protein was detected with anti-His antibody. E, Low-temperature-mediated degradation of FvCHS1 protein is accelerated in FvMAPK3-OE fruits. Total proteins from EV-OE and FvMAPK3-OE fruits were extracted for immunoblot analysis with anti-FvCHS1 antibody. Anti-actin was used as loading control. F, Relative FvKFB1 expression levels in EV-OE and FvMAPK3-OE fruits cultivated at 25°C (control conditions) or shifted to 4°C for 24 h. Values are means ± sem of three biological replicates. Statistical significance was determined by Tukey’s test; significant differences at the P < 0.05 level are indicated by different letters. G, FvKFB1 interacts with FvCHS1 in a Y2H assay.