BRs play important roles in the transition from skotomorphogenesis to photomorphogenesis by optimizing the biosynthesis of chlorophyll through the BZR1-PIF4-GRF

As sessile organisms, the precise development phase transitions are very important for the success of plant adaptability, survival and reproduction. The transition from juvenile to the adult phase—referred to as the vegetative phase change—is significantly influenced by numbers of endogenous and environmental signals. Here, we showed that brassinosteroid (BR), a major growth-promoting steroid hormone, positively regulates the vegetative phase change in Arabidopsis thaliana. The BR-deficient mutant det2-1 and BR-insensitive mutant bri1-301 displayed the increased ratio of leaf width to length and reduced blade base angle. The plant specific transcription factors SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) are key masters for the vegetative phase transition in plants. The expression levels of SPL9, SPL10 and SPL15 were significantly induced by BR treatment, but reduced in bri1-116 mutant compared to wild-type plants. The gain-of-function pSPL9:rSPL9 transgenic plants displayed the BR hypersensitivity on hypocotyl elongation and partially suppressed the delayed vegetative phase change of det2-1 and bri1-301. Furthermore, we showed that BRASSINAZOLE-RESISTANT 1 (BZR1), the master transcription factor of BR signaling pathway, interacted with SPL9 to cooperatively regulate the expression of downstream genes. Our findings reveal an important role for BRs in promoting vegetative phase transition through regulating the activity of SPL9 at transcriptional and post-transcriptional levels.

Plant architecture is crucial for rapeseed breeding. Here, we demonstrate the involvement of BnERF114.A1, a transcription factor for ETHYLENE RESPONSE FACTOR (ERF), in the regulation of plant architecture in Brassica napus. BnERF114.A1 is a member of the ERF family group X-a, encoding a putative 252-amino acid (aa) protein, which harbours the AP2/ERF domain and the conserved CMX-1 motif. BnERF114.A1 is localised to the nucleus and presents transcriptional activity, with the functional region located at 142–252 aa of the C-terminus. GUS staining revealed high BnERF114.A1 expression in leaf primordia, shoot apical meristem, leaf marginal meristem, and reproductive organs. Ectopic BnERF114.A1 expression in Arabidopsis reduced plant height, increased branch and silique number per plant, and improved seed yield per plant. Furthermore, in Arabidopsis, BnERF114.A1 overexpression inhibited indole-3-acetic acid (IAA) efflux, thus promoting auxin accumulation in the apex and arresting apical dominance. Therefore, BnERF114.A1 probably plays an important role in auxin-dependent plant architecture regulation.

Plant architecture is very important for rapeseed breeding. Here, we reported an ETHYLENE RESPONSE FACTOR (ERF) transcription factor BnERF114.A1 of Brassica napus participating in plant architecture regulation. BnERF114.A1 is a member of ERF family group x-a, encoding a putative protein of 252 aa which consisting of an AP2/ERF domain and a conserved CMX-1 motif. BnERF114.A1 located in nucleus and had transcriptional activity with its functional region located in 142 aa ~ 252 aa of its C-terminus. The GUS staining analysis revealed that BnERF114.A1 highly expressed in leaf primordia, shoot apical meristem, leaf marginal meristem, and reproductive organs. Ectopic expression of BnERF114.A1 in Arabidopsis reduced plant height, increased branch numbers and silique numbers per plants, and finally increased seed yield per plant. Further investigation demonstrated that overexpression of BnERF114.A1 can inhibit IAA efflux and cause accumulation of auxin in apex, and arrest apical dominance in Arabidopsis. The findings suggested BnERF114.A1 could provide a candidate gene for rapeseed plant architecture molecular breeding.