Figure 9.

GUS/LUC Assay and the Working Model of CsFUL1 Regulating Fruit Length in Cucumber.

(A) and (B) Quantification of GUS activities in N. benthamiana leaves after transient expression of Pro35S:CsFUL1^A, Pro35S:CsFUL1^C, and Pro35S:CsAGL20 with ProCsFUL1:GUS (A) or ProCsPIN7:GUS (B). Four independent transfection experiments were performed for each combination. Values are means ± se. Significance analysis was conducted with the two-tailed Student's t tests (*P < 0.05; **P < 0.01).

(C) CsFUL1^A controls fruit elongation via two regulatory pathways. Upon binding of CsFUL1^A with CsAGL20 and/or other as-yet unidentified proteins (gray square) to form an active polymer complex, (1) CsFUL1^A binds to the CArG-box to inhibit CsSUP expression and thus regulates cell division and cell expansion; and (2) CsFUL1^A downregulates the expression of CsPIN1 and CsPIN7, resulting in decreases in auxin accumulation in the fruit. The active polymer may feedback on CsFUL1^A to maintain its expression at appropriate levels and thus maintain proper levels of auxin accumulation for fruit elongation. Black arrows, positive regulation; black boxes, CArG-box; crosses, inhibit of transcription; lines, promoter region; red arrows, transcription start.

(D) Evolutionary diagram of the generation of the CsFUL1^A allele in the East Asian long-fruited cucumbers during domestication and diversification.