Abstract
The genetic network controlling flowering and flower development consists of a set of floral integrator genes that play a role in light sensing, hormone signaling and developmental pathways. These integrators activate the expression of meristem identity genes LEAFY (LFY) and APETALA1 (AP1) to initiate the flowering transition. However, how the expression of key genes, such as AP1, responds to diverse signals during flower development remains largely unknown. Here, we report that an Arabidopsis abnormal flower development inbred line (AFDL) exhibits a phenotype similar to the ap1 mutant, with delayed flowering time and a high frequency of transition of flower meristems into inflorescence meristems after flowering. The flower organs with an abnormal first whorl lack the second whorl and the increased number of inflorescences at the first- and second-whorl positions most closely resembled the phenotypes of ap1/cal double mutants. Interestingly, both normal and abnormal flowers coexisted in a single individual. Microarray and quantitative real-time PCR analysis revealed that the expression of AP1 was significantly reduced, while the expression of its interacting genes TERMINAL FLOWER 1 (TFL1), SHORT VEGETATIVE PHASE (SVP), AGAMOUS-like 24 (AGL24), SEPALLATA (SEP) and CAULIFLOWER (CAL) and upstream genes FLOWERING LOCUS C (FLC) and FLM were increased in AFDL, which could serve to explain its phenotype. The expression of genes responsive to different stimuli dramatically changed in AFDL relative to the wild type, as revealed by the differential display of transcripts, indicating that this expression variation is subject to a threshold, leading to an on/off expression pattern of the master regulatory gene (such as AP1) of flower development.
Highlights
The genetic network controlling flowering and flower development consists of a set of floral integrator genes that play a role in light sensing, hormone signaling and developmental pathways
abnormal flower development inbred line (AFDL) plants grew vigorously but exhibited variable degrees of phenotypic alteration compared to WT (Figure 1(a)) as follows: (i) more inflorescences stacked at a small angle to the stem (Figure 1(b)); (ii) long, thin inflorescences with a larger angle to the stem and longer internodes (Figure 1(c)); and (iii) infrequent coexistence of both WT and AFDL inflorescence phenotypes (Figure 1(d)–(f)) as well as the presence of both normal (Figure 1(g)) and abnormal flowers (Figure 1(h)) in the same plant (Figure 1(f))
Multiple flowers towards the axillary side showed a cauliflower-like shape, with no petals being observed in AFDL types (Figure 1(h)), which is very similar to ap1/cal double mutants
Summary
The genetic network controlling flowering and flower development consists of a set of floral integrator genes that play a role in light sensing, hormone signaling and developmental pathways These integrators activate the expression of meristem identity genes LEAFY (LFY) and APETALA1 (AP1) to initiate the flowering transition. The flowering time genetic network in A. thaliana represents one of the best-studied functional systems in plants, and integrates environmental and physiological information to modulate expression of key downstream genes controlling the appropriate time for flowering [3,4] These genes include FLOWERING LOCUS C (FLC), whose expression is regulated mainly by vernalization and an autonomous pathway, and CONSTANS (CO), regulated by an autonomous pathway [5]. The regulation of AP1 by endogenous and environmental cues warrants further investigation
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