Abstract
Strigolactones (SLs), a group of carotenoid derived terpenoid lactones, are root-to-shoot phytohormones suppressing shoot branching by inhibiting the outgrowth of axillary buds. DWARF 53 (D53), the key repressor of the SL signaling pathway, is speculated to regulate the downstream transcriptional network of the SL response. However, no downstream transcription factor targeted by D53 has yet been reported. Here we report that IdealPlantArchitecture1 (IPA1), a key regulator of the plant architecture in rice, functions as a direct downstream component of D53 in regulating tiller number and SL-induced gene expression. We showed that D53 interacts with IPA1 in vivo and in vitro and suppresses the transcriptional activation activity of IPA1. We further showed that IPA1 could directly bind to the D53 promoter and plays a critical role in the feedback regulation of SL-induced D53 expression. These findings reveal that IPA1 is likely one of the long-speculated transcription factors that act with D53 to mediate the SL-regulated tiller development in rice.
Highlights
Strigolactones (SLs), a collection of terpenoid-derived compounds produced by plants, were firstly identified as the host-derived germination signals of root parasitic plants [1], and later as stimulants of hyphal branching of arbuscular mycorrhizal fungi [2]
To understand whether loss-of-function mutations of Ideal Plant Architecture1 (IPA1) could affect rice plant architecture, especially tillering, we used a targeting induced local lesions in genomes (TILLING) method to generate point mutations in IPA1, which led to amino acid substitutions in the gene product
The ipa110 mutant resulted from a 5-bp deletion in the coding sequence; the ipa1-11 mutant arose from a 57-bp insertion in the replacement of 102-bp deletion in the coding sequence; ipa1-3D and ipa1-4D were gain-of-function mutants resulting from 12-bp and 21-bp in-frame deletions in the miRNA156/529 target sites respectively (Supplementary information, Figure S2), which abolish the miRNA regulation without interfering the normal function of IPA1
Summary
Strigolactones (SLs), a collection of terpenoid-derived compounds produced by plants, were firstly identified as the host-derived germination signals of root parasitic plants [1], and later as stimulants of hyphal branching of arbuscular mycorrhizal fungi [2]. DWARF14 (D14) encodes a member of the α/β-hydrolase fold family protein, which binds and hydrolyses SL to form a covalently linked intermediate molecule (CLIM) [11, 12, 15, 34,35,36,37]. Whether D53 regulates the transcription of genes in the endogenous SL signaling pathway and what are its direct downstream transcription factors remain to be determined. In other angiosperms such as Arabidopsis thaliana and pea, the orthologs of D14, D3 and D53 have similar functions [6, 7, 9, 41,42,43,44]
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