Figure 1.

Mutations in MLK4 Result in Late Flowering under a Long-Day Photoperiod.

(A) Gene structure of MLK4, indicating exons (boxes), introns (lines), and T-DNA insertions (triangles). The primers used for genotype analysis are marked with arrows.

(B) Genotypic analysis of the mlk4 mutants. The genotype was analyzed with the left genomic primer (LP), right genomic primer (RP), and the vector primer (LBb1.3). The positions of LP1, RP1, LP2, and RP2 are indicated in (A).

(C) The presence of full-length MLK4 transcript in the mlk4 mutants was examined by RT-PCR.

(D) The 32-d-old mlk4 mutants exhibit a delayed-flowering phenotype under a LD photoperiod.

(E) The total leaf number of Col-0 and mlk4 mutants under a LD photoperiod and SD photoperiod. Flowering time was assessed by counting the number of rosette leaves and cauline leaves at bolting under LD and SD. Values shown are mean ± sd of total leaves; 42 plants were scored for each line.

(F) The relative level of CO mRNA was examined in Col-0 and mlk4 mutants. The black bars indicate the dark period, and the white bars indicate the light period. Experiments were repeated at least three times, and each data point indicates the mean ±se, n = 3 replicates. ZT, Zeitgeber time. Asterisks indicate significant difference from Col-0 using Student’s t test (P < 0.05).

(G) The stable expression of Pro_CO:GUS was examined by staining in the leaves of Col-0 and mlk4-2 plants for GUS activity.

(H) Representative image of 40-d-old Col-0, mlk4-2, co9, and mlk4-2 co9 double mutant plants under a LD photoperiod.

(I) The total leaf number of Col-0, mlk4-2, co-9, and mlk4-2 co-9 plants under LD and SD. Flowering time was assessed by counting the number of rosette leaves and cauline leaves at bolting under LD and SD. Values shown are mean ± sd of total leaves; 42 plants were scored for each line.