Analysis of Graft Compatibility in Heterograft Combination of Cucurbitaceae

To understand the molecular mechanism takes place during graft compatible heterograft combination of cucurbitaceae, the seedlings of watermelon [Citrullus lanatus (Thunb.)] cultivar ‘8424’ and melon (Cucumis melo L.) cultivar ‘Yongtian No. 3’ were grafted onto the compatible rootstock of winter squash (Cucurbita maxima duch.ex lam) A (TLZ-B2-1-24) to format the compatibility response of heterograft combination of watermelon/ winter squash A (abb. W/A) and melon/ winter squash A (abb. M/A), respectively. The whole protein change during various grafting developmental stages was studied by SDS-PAGE electrophoresis. A decrease in a 39 kDa callus protein band at the winter squash A was observed during the 10 days after grafting, and the callus proteins of scion (watermelon and melon) were still kept. Differentially expressed protein profile of the W(M)/A (No.5 day) and W(M)/A (No.10 day) were compared by 2-DE analysis. The results showed there were 38 and 8 differentially expressed protein spots with a significant difference at (P<0.05) and fold change (fold>3.0) in W/A and M/A, respectively. The number of protein spots belongs to the degradation, down-regulated, abundance and up-regulated was 27 (W/A+M/A, 23+4), 4 (W/A+M/A, 3+1), 5 (W/A+M/A, 2+3) and 10 (W/A+M/A, 10+0), respectively. Sixteen degradation and down-regulated protein spots of W(M)/A (No.10 day) were analyzed by MALDI-TOF MS. Ten proteins were identified, which were involved in saccharometabolism, metabolism and signal transduction. Moreover, the fructokinase was detected in both W/A and M/A, which may indicated that saccharometabolism played the important role during the compatible heterograft combination formation in cucurbitaceae.