early bolting in short days: an Arabidopsis mutation that causes early flowering and partially suppresses the floral phenotype of leafy - PubMed (original) (raw)

. 2001 May;13(5):1011-24.

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early bolting in short days: an Arabidopsis mutation that causes early flowering and partially suppresses the floral phenotype of leafy

C Gómez-Mena et al. Plant Cell. 2001 May.

Abstract

The time of flowering in Arabidopsis is controlled by multiple endogenous and environmental signals. Some of these signals promote the onset of flowering, whereas others repress it. We describe here the isolation and characterization of two allelic mutations that cause early flowering and define a new locus, EARLY BOLTING IN SHORT DAYS (EBS). Acceleration of flowering time in the ebs mutants is especially conspicuous under short-day photoperiods and results from a reduction of the adult vegetative phase of the plants. In addition to the early flowering phenotype, ebs mutants show a reduction in seed dormancy, plant size, and fertility. Double mutant analysis with gibberellin-deficient mutants indicates that both the early-flowering and the precocious-germination phenotypes require gibberellin biosynthesis. Analysis of the genetic interactions among ebs and several mutations causing late flowering shows that the ft mutant phenotype is epistatic over the early flowering of ebs mutants, suggesting that the precocious flowering of ebs requires the FT gene product. Finally, the ebs mutation causes an increase in the level of expression of the floral homeotic genes APETALA3 (AP3), PISTILLATA (PI), and AGAMOUS (AG) and partially rescues the mutant floral phenotype of leafy-6 (lfy-6) mutants. These results suggest that EBS participates as a negative regulator in developmental processes such as germination, flowering induction, and flower organ specification.

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Figures

Figure 1.

Figure 1.

Phenotype of ebs Mutants. (A) L_er_ (left), ebs-1 (middle), and ebs-2 (right) 5-week-old plants grown under LD (top) or SD (bottom). (B) Average number of juvenile, adult, or cauline leaves for L_er_ and ebs mutants grown under LD or SD photoperiods. Bars indicate ±

se

. (C) Flowers from L_er_ (left), ebs-1 (middle), and ebs-2 (right).

Figure 2.

Figure 2.

Effect of the ebs Mutation on Total Leaf Number of ga1-3, ga2-1, and spy-5 Mutants. (A) Total leaf number under LD. (B) Total leaf number under SD. Asterisks indicate that plants were unable to flower after 3 months of growth under SD. During this time, they produced 65 leaves. (C) Phenotype of ebs-1 (left), ebs-1 ga1-3 (middle), and ga1-3 (right) 5-week-old plants grown under LD. Error bars in (A) and (B) indicate ±

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.

Figure 3.

Figure 3.

Reduction in the Dormancy of ebs Mutant Seeds and Its Effect on the Germination of Double Mutants with ga1-3 and spy-5. Germination was scored after 2 weeks of incubation except in (C), where germination was scored as indicated. (A) Germination of L_er_, ebs-1, and ebs-2 seeds after different weeks of storage. (B) Germination rates of L_er_, ebs-1, ga1-3, and ebs-1 ga1-3 freshly harvested seeds in the presence of different GA concentrations. (C) Time course of germination of L_er_, ebs-1, spy5, and ebs-1 spy-5 freshly harvested seeds. (D) Germination rates of L_er_, ebs-1, spy5, and ebs-1 spy-5 freshly harvested seeds in the presence of different concentrations of PAC.

Figure 4.

Figure 4.

Effect of the ebs Mutation on Total Leaf Number of Late- Flowering Mutants Affecting the LD Pathway and the Autonomous Pathway. (A) Total leaf number under LD. (B) Total leaf number under SD. (C) Phenotype of ebs-1 (left), ft-1 (middle), and ebs-1 ft-1 (right) 5-week-old plants grown under LD. Error bars in (A) and (B) indicate ±

se

.

Figure 5.

Figure 5.

Partial Rescue of the lfy-6 Floral Phenotype by the ebs Mutation. (A) Inflorescence of a lfy-6 mutant plant grown under LD. (B) Inflorescence of an ebs-1 lfy-6 double mutant plant grown under LD. (C) Inflorescence of an ebs-1 lfy-6 double mutant plant grown under SD. (D) Flower from an SD-grown ebs-1 lfy-6 plant showing the partial rescue of petals and stamens.

Figure 6.

Figure 6.

Expression of AP3, PI, and AG in ebs-1 and the ebs-1 lfy-6 Double Mutant. Total RNA was isolated from reproductive apices or leaves of LD-grown plants, and 20 μg was loaded in each lane. Blots were probed with radiolabeled AP3, PI, and AG cDNAs and then reprobed with rDNA as a loading control. (A) Steady state levels of AP3, PI, and AG mRNA in apices and leaves of L_er_ and ebs mutants. (B) Steady state levels of AP3, PI, and AG mRNA in apices of ebs-1, lfy-6, and ebs-1 lfy-6 plants.

Figure 7.

Figure 7.

Pattern of Expression of AP3 and AG in Floral Meristems of ebs and Inflorescences of the ebs-1 lfy-6 Double Mutant. The expression of AP3 and AG was analyzed by in situ hybridization on longitudinal sections of apical buds from plants grown under LD. (A) L_er_ stage 3 flower probed with AP3. (B) ebs-1 stage 3 flower probed with AP3. (C) L_er_ stage 3 flower probed with AG. (D) ebs-1 stage 3 flower probed with AG. (E) L_er_ stage 6 flower probed with AP3. (F) ebs-1 stage 6 flower probed with AP3. (G) L_er_ stage 5 flower probed with AG. (H) ebs-1 stage 5 flower probed with AG. (I) L_er_ stage 9 flower probed with AP3. (J) ebs-1 stage 9 flower probed with AP3. (K) L_er_ stage 9 flower probed with AG. (L) ebs-1 stage 9 flower probed with AG. (M) lfy-6 mutant inflorescence probed with AP3. (N) ebs-1 lfy-6 double mutant inflorescence probed with AP3. (O) lfy-6 mutant inflorescence probed with AG. (P) ebs-1 lfy-6 double mutant inflorescence probed with AG.

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