Abstract
The APETALA 2/ethylene response factors (AP2/ERF) are widespread in the plant kingdom and play essential roles in regulating plant growth and development as well as defense responses. In this study, a novel rice AP2/ERF transcription factor gene, OsRPH1, was isolated and functionally characterized. OsRPH1 falls into group-IVa of the AP2/ERF family. OsRPH1 protein was found to be localized in the nucleus and possessed transcriptional activity. Overexpression of OsRPH1 resulted in a decrease in plant height and length of internode and leaf sheath as well as other abnormal characters in rice. The length of the second leaf sheath of OsRPH1-overexpressing (OE) plants recovered to that of Kitaake (non-transgenic recipient) in response to exogenous gibberellin A3 (GA3) application. The expression of GA biosynthesis genes (OsGA20ox1–OsGA20ox4, OsGA3ox1, and OsGA3ox2) was significantly downregulated, whereas that of GA inactivation genes (OsGA2ox7, OsGA2ox9, and OsGA2ox10) was significantly upregulated in OsRPH1-OE plants. Endogenous bioactive GA contents significantly decreased in OsRPH1-OE plants. OsRPH1 interacted with a blue light receptor, OsCRY1b, in a blue light-dependent manner. Taken together, our results demonstrate that OsRPH1 negatively regulates plant height and bioactive GA content by controlling the expression of GA metabolism genes in rice. OsRPH1 is involved in blue light inhibition of leaf sheath elongation by interacting with OsCRY1b.
Highlights
APETALA 2/ethylene response factors (AP2/ERF) family, a plant-specific transcription factor superfamily, is characterized by a highly conserved APETALA 2 (AP2) DNA-binding domain (Nakano et al, 2006; Rashid et al, 2012; Gu et al, 2017)
AP2/ERF transcription factor family regulates agronomic traits, including plant growth, defense responses, and fruit ripening through mediating phytohormonal biosynthesis and signals (Gu et al, 2017)
A total of 170 AP2/ERF genes have been identified in rice genome, and several AP2/ERF members play roles in controlling plant growth and development via integrating different phytohormonal signals (Xu et al, 2006; Fukao and Bailey-Serres, 2008; Yaish et al, 2010; Qi et al, 2011). miR172-mediated HvAP2 controls internode elongation in barley (Patil et al, 2019)
Summary
AP2/ERF family, a plant-specific transcription factor superfamily, is characterized by a highly conserved APETALA 2 (AP2) DNA-binding domain (Nakano et al, 2006; Rashid et al, 2012; Gu et al, 2017). OsEATB, a rice AP2/ERF gene, restricts internode elongation by downregulating the GA biosynthetic gene, ENT-COPALYL DIPHOSPHATE SYNTHASE 2 (Os2) (Qi et al, 2011). Another ERF gene, SUBMERGENCE1A (SUB1A), confers submergence tolerance in rice by limiting ethylenepromoted GA responses during submergence wherein Sub1A enhances the accumulation of GA signaling repressors SLENDER RICE 1 (SLR1) and SLR1 LIKE-1 (SLRL1) (Xu et al, 2006; Fukao and Bailey-Serres, 2008). Overexpression of OsAP2-39 leads to overall biomass reduction, including seed yield, and OsAP239 directly activates the ABA biosynthesis gene OsNCED1 and the GA inactivating gene ELONGATED UPPERMOST INTERNODE1(OsEUI1) (Yaish et al, 2010)
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