Disease relevance of AGL20

• When the Brassica AGL20 ortholog was constitutively expressed in sense and antisense orientations using the 35S cauliflower mosaic virus promoter, some of the sense transgenic plants flowered extremely early and some of the antisense plants exhibited delayed flowering [1].

High impact information on AGL20

• The SOC1 and FT genes are also regulated by a second flowering-time pathway that acts independently of CO [2].
• An FLC:HA fusion protein binds directly in vivo to the promoter regions of FD and SOC1 and to the first intron of FT [3].
• A MADS-domain gene, AGAMOUS-LIKE 20 (AGL20), was identified as a dominant FRI suppressor in activation tagging mutagenesis [4].
• The AGAMOUS-LIKE 20 MADS domain protein integrates floral inductive pathways in Arabidopsis [4].
• Antagonistic regulation of flowering-time gene SOC1 by CONSTANS and FLC via separate promoter motifs [5].

Biological context of AGL20

• The up-regulated genes included AGL20 and AGL9, which most likely cause the early flowering phenotype of 35S::SHL plants [6].
• Late-flowering SHL-antisense lines showed reduced AGL20 mRNA levels, suggesting that AGL20 gene expression depends on the SHL protein [6].
• We show that in transgenic plants overexpressing CO and FLC, these proteins regulate flowering time antagonistically and FLC blocks transcriptional activation of SOC1 by CO [5].
• The fourth suppressor mutation is an allele of fwa, and fwa soc1 35S::CO plants flowered at approximately the same time as co mutants, suggesting that a combination of fwa and soc1 abolishes the promotion of flowering by CO [7].
• These genes function in 'cascades' within four promotive pathways, the 'photoperiodic', 'autonomous', 'vernalization', and 'gibberellin' pathways, which all converge on the 'integrator' genes SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1) and FLOWERING LOCUS T (FT) [8].

Associations of AGL20 with chemical compounds

• Rather, expression of FT and SOC1/AGL20 was repressed by 1% (w/v) Suc in wild-type background [9].
• Two of these genes, SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1) and FLOWERING LOCUS T (FT), are required for CO to promote flowering; the others are involved in proline or ethylene biosynthesis [2].
• In order to determine if its role is conserved in other plants, we isolated AGL20 orthologs from Brassica campestris, Cardamine flexuosa and Draba nemorosa [1].

Other interactions of AGL20

• Taken together, these data suggest that CO activates SOC1 through FT to promote flowering in Arabidopsis [10].
• However, this genetic analysis was inconsistent with the sequential induction pattern of FT and SOC1 found in inducible CO overexpressor plants [10].
• FT and SOC1 share the common upstream regulators CO, a key component in the long day pathway, and FLC, a flowering repressor integrating autonomous and vernalization pathways [11].
• Further genetic analyses of epistasis indicate that AGL24 may act downstream of SOC1 and upstream of LFY [12].
• In Arabidopsis, several genetic pathways controlling the floral transition (flowering) are integrated at the transcriptional regulation of FT, LFY and SOC1 [13].

Analytical, diagnostic and therapeutic context of AGL20

• Using chromatin immunoprecipitation, we have shown that FLC binds to a region of the first intron of FT that contains a putative CArG box, and have confirmed that FLC binds to a CArG box in the promoter of the SOC1 gene [14].

References