IPA1 functions as a downstream transcription factor repressed by D53 in strigolactone signaling in rice

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 Ideal Plant Architecture 1 (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.

Developmental analysis of the early steps in strigolactone‐mediated axillary bud dormancy in rice

“…Consequently, we demonstrated that dormant genes, including DRM1 to DRM4 and OsNCED1 , were upregulated in the leaf primordia rather than in the meristem of the axillary bud. Recently, it was reported that SLs work at least partly through OsSPL14 to suppress bud outgrowth in rice (Song et al ., ). We showed that OsSPL14 mRNA exclusively accumulates in the leaf primordia and is excluded from the axillary meristem as well as the SAM (Luo et al ., ).…”

“…Accumulation of PIN protein on the plasma membrane is enhanced in the absence of SL, allowing establishment of auxin flow between the axillary bud and the main stem (Crawford et al, 2010;Shinohara et al, 2013). In the second proposed mode of SL action, SL works through the control of downstream transcription cascades (Braun et al, 2012;Brewer et al, 2015;Liu et al, 2017;Song et al, 2017). In rice and wheat, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes, encoding plant-specific transcription factors, were identified as D53 targets that suppress bud outgrowth (Liu et al, 2017;Song et al, 2017).…”

“…In the second proposed mode of SL action, SL works through the control of downstream transcription cascades (Braun et al, 2012;Brewer et al, 2015;Liu et al, 2017;Song et al, 2017). In rice and wheat, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes, encoding plant-specific transcription factors, were identified as D53 targets that suppress bud outgrowth (Liu et al, 2017;Song et al, 2017). We have shown previously that FINE CULM1 (FC1), a TCP transcription factor, is required for SL to inhibit bud outgrowth (Minakuchi et al, 2010).…”

Strigolactones in plant adaptation to abiotic stresses: An emerging avenue of plant research

“…The newly formed protein complex polyubiquitinates transcriptional repressors D53/SMXL6/7/8, thereby triggering 26S proteasome‐mediated degradation of D53/SMXL6/7/8 that allows the expression of SL‐responsive genes for various physiological functions (Figure b; Waters et al, ; Yao et al, ). For instance, it has recently been reported in rice that IDEAL PLANT ARCHITECTURE1, a SQUAMOSA PROMOTER BINDING PROTEIN‐LIKE transcription factor, acts as a direct downstream target of D53 in regulating tiller development and SL‐mediated gene expression (Song et al, ).…”

Systems model‐guided rice yield improvements based on genes controlling source, sink, and flow

“…In addition, DLT controls rice tillering and plant height through influencing the BR signaling pathway (Tong et al ). D53 interacts with IPA1, influencing IPA1 transcriptional activity and tillering (Song et al ), whereas IPI1 controls the tissue‐specific degradation of IPA1 and hence, regulates tillering and the number of primary and secondary rachis branches (Wang et al ).…”