Fig. 1

Phylogenetic relationship of SWEETs from cotton, Arabidopsis, rice, cacao, poplar, sorghum, cucumber and maize. The phylogenetic tree was generated using MEGA 6.0 with the NJ method with 1 000 bootstrap replicates. MEGA 7.0 was used for constructing the NJ tree. The I clade, II clade, III clade, and IV clade is marked in cyan, purple, blue and pink, respectively. Each clade was classified into sub-clades, marked in different colors on the circle. α to γ represent the sub-clades in the I clade, δ and ζ represent the sub-clades in the II clade, η to λ represent the sub-clades in the III clade, and μ to ξ represents the IV clade. The prefixes Ga, Gr, Gh, Potri, At, Os, GRMZM, Sobic, and Thecc stand for G. arboreum, G. raimondii, G. hirsutum, Populus trichocarpa, Arabidopsis thaliala, Oryza sativa, Zea mays, Sorghum bicolor, and Theobroma cacao, respectively. The appendices At and Dt in the upland cotton indicate the A- and D-subgenome, respectively. The bootstrap values are shown near the nodes, and only those values greater than 50 are displayed