Fig. 4: SUG1 interacts with OsSPL13 to control seed size.

a SUG1 associates with OsSPL13 in N. benthamiana leaves. b SUG1 associates with SUG1 in vivo. GFP-OsSPL13 and MYC-SUG1 were transiently expressed in N. benthamiana leaves. Total proteins from leaves were isolated and incubated with GFP-Trap-A agarose beads. The precipitated proteins were detected using anti‐GFP and anti‐MYC antibodies, separately. IB: immunoblot. IP: immunoprecipitation. c OsSPL13 interacts with SUG1 in vitro. The purified GST-OsSPL13 was incubated with MBP-SUG1 and pulled down by Glutathione‐Sepharose beads. The precipitates were detected by immunoblot with anti‐GST and anti‐MBP antibodies. d The dual-luciferase assays shown the transcriptional activation activities of SPL13, and the SUG1 could enhance the transcriptional activation activities of SPL13 in rice protoplasts. The luciferase (LUC)/renilla (REN) activity were measured by co-transformation of different effector construct and reporter constructs. The activity of the empty vector was set to one. Data are presented as mean ± SD. Two-tailed unpaired Student’s t-test was used for statistical analysis. n = 3 biological replicates. e Mature rice grains of ZH11, proACTIN:OsSPL13, sug1-cr, and sug1-cr proACTIN:OsSPL13. f Relative transcript level of OsSPL13 of ZH11, proACTIN:OsSPL13, sug1-cr, and sug1-cr proACTIN:OsSPL13. n = 3 biological replicates. g–h Grain length (g) and grain width (h) of ZH11 (n = 50), proACTIN:OsSPL13 (n = 56), sug1-cr (n = 60), and sug1-cr proACTIN:OsSPL13 (n = 51). Data in (f–h) are presented as mean ± SD. Different letters represent significant differences (P < 0.05) from ordinary one-way ANOVA multiple comparisons with Tukey’s multiple comparisons test. Bar = 3 mm (e). Experiments in (a-d) were repeated independently at least twice with similar results. Source data are provided as a Source data file.