Fig. 1. Effects of developmental regulators (DRs) on watermelon transformation. (a) Schematic diagrams of constructs with DRs used in this study. (b) Genetic transformation of the watermelon cultivar WW150. b1, watermelon seeds after sterilization; b2, 4-d-old watermelon seedlings; b3, cotyledon fragments after co-cultivation; b4, callus formed on the selection medium after two weeks; b5, adventitious buds on the callus; b6, adventitious root formed on the regenerated plants; b7, seedlings with roots on the rooting medium (left is a transgenic plant; right is a non-transgenic plant); b8, the same plants as in b6 with the picture taken under a hand-held florescence detection device. Scale bars=0.5 cm. (c) The transformation efficiencies of watermelon cultivar WW150 obtained using the indicated constructs. Positive transformation events were defined as calli showing at least one regenerated adventitious bud expressing the DsRed fluorescent signal. (d) Representative images of adventitious shoots generated by the indicated vectors (upper panels). The fluorescent DsRed2 signals are shown in the lower panels. Scale bars=0.5 cm. (e) The growth phenotype of a watermelon plant transformed with the pW502 vector two weeks after being transferred to soil. Scale bar=4 cm. RB: right border; LB: left border.