Fig. 1. Map-based cloning of SAO gene. A, Fine localization and mutation site analysis of SAO gene (LOC_Os11g12740). B-E, Comparison of mature plants (B), leaf width (C), grain width (D), and internode width (E) of Xinong 1B (wild type, WT), sao mutant (center), and complementary plants (SAO-C1 and SAO-C2). Scal bars are 10 cm (B), 2 cm (C), 1 cm (D), and 7 cm (E), respectively. F-H, Statistics of leaf width (F), internode width (G), and grain width (H) in WT, sao, and complementary plants. In F-H, data are mean ± SD (n = 10 for F and G; n = 50 for H). Different lowercase letters above bars indicate significant differences at the 0.05 level using the Tukey’s HSD test.

Fig. 2. Effect of SAO on expression of cell cycle-related genes. A, qRT-PCR analysis of the relative expression levels of CDKB2, His4, His1, CYCD3, and DEP1 in Xinong 1B (wild type, WT) and sao mutant. Actin (LOC_Os03g50885) was used as an internal control. Aboveground parts of rice organs at the seedling stage were collected for qRT-PCR analysis. Data are mean ± SD (n = 3). B, Gene clustering heatmap analysis of differentially expressed genes in A. C and D, In situ hybridization analysis of the expression pattern of CDKB2 gene in WT (C) and sao (D). Red and black curves represent P1 and P2 primordia, respectively. E, Frequency of CDKB2-expressing cells in C and D leaf primordia. F and G, In situ hybridization analysis of the expression pattern of His4 gene in WT (F) and sao (G). Red and black curves represent P1 and P2 primordia, respectively. H, Frequency of His4-expressing cells in F and G leaf primordia. The frequency of CDKB2- (E) and His-expressing cells (H) was calculated as follows: (Number of stained cells in P1 primordia) × (Area of individual cells in P1 primordia) / (Area of P1 primordia). The same calculation was applied to P2 and P3 primordia. In A, E, and H, *, P < 0.05; **, P < 0.01; ns indicates no significant differences using t-test. Scale bars in C, D, F, and G are 100 μm.