Genetic interaction between WUS and HAM family members. (a, b) The secondary inflorescence meristems initiated from axillary meristems in wus-7; ham1;2 homozygotes with ham3/+ terminate prematurely. (c)wus-7; ham1;2 homozygotes with ham4/+ display early termination of the main inflorescence meristem and lack of carpels in flowers (indicated by arrow). (d–f) WUS and HAM family members interact genetically in a dose-dependent manner. wus-7 (d) formed functional shoot apices and normal stature, but wus-7; ham1/+; ham2/+; ham3/+ (e) enhanced the wus-7 phenotype, and wus-7; ham1/+; ham2; ham3 (f) showed stronger enhancement, with reduced flower numbers and plant stature, and elongated vegetative stage, resembling a wus strong allele. Plants are 36 days after germination. (g–h) Down-regulation of HAM1, HAM2 and HAM3 in ham4 shoot meristems leads to an early termination phenotype. Compared to wild type (Col) (g), pWUS::mir171 in ham4 (h) showed terminated vegetative meristems. (i–l) WUS is required for functions of HAM1, HAM2 and HAM3. At 11 days after germination, compared to Ler wild type (i) and ham1;2;3 (k) which formed functional vegetative meristem and leaf primordia, wus-1; ham1;2;3 (l) displays terminated vegetative meristems similar to wus-1 (j). Bars = 2 mm.