HighlightLPA1 suppresses auxin signalling that interacts with C-22-hydroxylated and 6-deoxo brassinosteroids, which regulates lamina inclination independently of OsBRI1.

SummaryIndeterminate domain (IDD) genes are a family of plant transcriptional regulators that function in the control of development and metabolism during growth. Here, the function of Oryza sativa indeterminate domain 10 (OsIDD10) has been explored in rice plants. Compared with wild-type roots, idd10 mutant roots are hypersensitive to exogenous ammonium. This work aims to define the action of IDD10 on gene expression involved in ammonium uptake and nitrogen (N) metabolism.The ammonium induction of key ammonium uptake and assimilation genes was examined in the roots of idd10 mutants and IDD10 overexpressors. Molecular studies and transcriptome analysis were performed to identify target genes and IDD10 binding cis-elements.IDD10 activates the transcription of AMT1;2 and GDH2 by binding to a cis-element motif present in the promoter region of AMT1;2 and in the fifth intron of GDH2. IDD10 contributes significantly to the induction of several genes involved in N-linked metabolic and cellular responses, including genes encoding glutamine synthetase 2, nitrite reductases and trehalose-6-phosphate synthase. Furthermore, the possibility that IDD10 might influence the Nmediated feedback regulation of target genes was examined.This study demonstrates that IDD10 is involved in regulatory circuits that determine N-mediated gene expression in plant roots.

The promotive effects of brassinosteroids (BRs) on plant growth and development have been widely investigated; however, it is not known whether BRs directly affect nutrient uptake. Here, we explored the possibility of a direct relationship between BRs and ammonium uptake via AMT1-type genes in rice (Oryza sativa). BR treatment increased the expression of AMT1;1 and AMT1;2, whereas in the mutant d61-1, which is defective in the BR-receptor gene BRI1, BR-dependent expression of these genes was suppressed. We then employed Related to ABI3/VP1-Like 1 (RAVL1), which is involved in BR homeostasis, to investigate BR-mediated AMT1 expression and its effect on NH4+ uptake in rice roots. AMT1;2 expression was lower in the ravl1 mutant, but higher in the RAVL1-overexpressing lines. EMSA and ChIP analyses showed that RAVL1 activates the expression of AMT1;2 by directly binding to E-box motifs in its promoter. Moreover, 15NH4+ uptake, cellular ammonium contents, and root responses to methyl-ammonium strongly depended on RAVL1 levels. Analysing AMT1;2 expression levels in different crosses between BRI1 and RAVL1 mutant and overexpression lines indicated that RAVL1 acts downstream of BRI1 in the regulation of AMT1;2. Thus, the present study shows how BRs may be involved in the transcriptional regulation of nutrient transporters to modulate their uptake capacity.

Rice (Oryza sativa) is the most important consumed staple food for a large and diverse population worldwide. Since databases of genomic sequences became available, functional genomics and genetic manipulations have been widely practiced in rice research communities. Insertional mutants are the most common genetic materials utilized to analyze gene function. To mutagenize rice genomes, we exploited the transpositional activity of an Activator/Dissociation (Ac/Ds) system in rice. To mobilize Ds in rice genomes, a maize Ac cDNA was expressed under the CaMV35S promoter, and a gene trap Ds was utilized to detect expression of host genes via the reporter gene GUS. Conventional transposon‐mediated gene‐tagging systems rely on genetic crossing and selection markers. Furthermore, the activities of transposases have to be monitored. By taking advantage of the fact that Ds becomes highly active during tissue culture, a plant regeneration system employing tissue culture was employed to generate a large Ds transposant population in rice. This system overcomes the requirement for markers and the monitoring of Ac activity. In the regenerated populations, more than 70% of the plant lines contained independent Ds insertions and 12% expressed GUS at seedling stages. This protocol describes the method for producing a Ds‐mediated insertional population via tissue culture regeneration systems. © 2016 by John Wiley & Sons, Inc.