AHL26, an AT-hook gene, negatively regulates hypocotyl growth and flowering time in Arabidopsis thaliana

Background The AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED (AHL) gene family in Arabidopsis contains 29 members, which evolved into two phylogenetic clades. Genes from this family play a role in several biological processes, but most of the members' functions remain unknown. Results Here, we provide evidence that AHL26, a clade-a protein, negatively regulates hypocotyl growth and flowering time in Arabidopsis. Analysis of transgenic plants expressing an AHL26:AHL26:GUS translational fusion driven by 1.9 KB of the endogenous AHL26 promoter displayed GUS activity in the hypocotyl and apical meristem of light-grown seedlings. The overexpression of AHL26 resulted in the inhibition of hypocotyl growth and delayed flowering. However, the overexpression of a dominant-negative AHL26 with mutation in AT-hook motif, resulted in early flowering and longer hypocotyls than the WT and over-expression transgenic lines suggesting genetic redundancy between AHL26 and other AHL genes. Transcriptome analysis showed that the regulation of flowering time in AHL26 over-expression and dominant-negative mutants results from regulating flowering-related genes and pathways. Conclusion Our study highlights the significant role of AHL26 in hypocotyl growth and flowering time regulation. We further demonstrate that AHL26 regulates hypocotyl length in a light-dependent manner. Through transcriptomic analysis, we also show that the delayed flowering phenotype in our AHL26 over-expression plants is due to the negative regulation of flowering-promoting genes such as FT. Furthermore, transcriptome analysis provides insight into the biological processes and pathways through which AHL26 influences the control of flowering time.