IPA1: a direct target of SL signaling

Abstract

The plant hormone strigolactone (SL) is important for many processes in plants, but its molecular mode of action has been difficult to elucidate. A new discovery has identified the SPL transcription factor, IPA1, as a crucial component directly involved in SL signaling.

Figure 1

Simplified rice-centric model of SL signaling in the regulation of shoot branching/tillering. SL degrades the D53 protein in rice^, and the related SMXL6, SMXL7 and SMXL8 proteins in Arabidopsis. D53 directly prevents the transcriptional activation function of IPA1 (OsSPL14) in rice and the related SPL3 and SPL17 proteins in wheat ; D53 prevents IPA1 upregulation of D53 gene expression in rice, and TaSPL3 upregulation of TaTB1 gene expression in wheat. IPA1 regulation of TB1 gene expression in rice has also been confirmed even though SL regulation of TB1 has not been reported in rice. TB1 can then inhibit shoot branching/tillering via unknown mechanisms. miR156 integrates many environmental and endogenous signals and post-transcriptionally regulates IPA1 gene expression.