SMOS1,SHB,RLA1

• Symbol: SMOS1,SHB,RLA1
• MSU: LOC_Os05g32270
• RAPdb: Os05g0389000

• LOC_Os05g32270.1: 0.3032
• LOC_Os05g32270.2: 0.9574

• LOC_Os05g32270.1: 0
• LOC_Os05g32270.2: 0

• NA

• A novel AP2-type transcription factor, SMALL ORGAN SIZE1, controls organ size downstream of an auxin signaling pathway, 2014, Plant Cell Physiol.
• SHOEBOX Modulates Root Meristem Size in Rice through Dose-Dependent Effects of Gibberellins on Cell Elongation and Proliferation., 2015, PLoS Genet.
• The RLA1/SMOS1 Transcription Factor Functions with OsBZR1 to Regulate Brassinosteroid Signaling and Rice Architecture., 2017, Plant Cell.

Genbank accession number

• SMOS1 expression was induced by exogenous auxin treatment, and the auxin response element (AuxRE) of the SMOS1 promoter acts as a cis-motif through interaction with auxin response factor (ARF)
• We propose that SMOS1 acts as an auxin-dependent regulator for cell expansion during organ size control, and that its function is conserved among land plants
• In this study, we identified a new rice loss-of-function mutant, small organ size1 (smos1), that decreases the final size of various organs due to decreased cell size and abnormal microtubule orientation
• Furthermore, a functional fluorophore-tagged SMOS1 was localized to the nucleus, supporting the role of SMOS1 as a transcriptional regulator for organ size control
• SMOS1 encodes an unusual APETALA2 (AP2)-type transcription factor with an imperfect AP2 domain, and its product belongs to the basal AINTEGUMENTA (ANT) lineage, including WRINKLED1 (WRI1) and ADAP
• Quantitative analysis of cortical cell length and number indicates that shb has shorter, rather than fewer, cells in the root meristem until around the fifth day after sowing, from which the number of cortical cells is also reduced
• SHB encodes an AP2/ERF transcription factor that directly activates transcription of the GA biosynthesis gene KS1
• These defects can be either corrected by exogenous application of bioactive GA or induced in wild-type roots by a dose-dependent inhibitory effect of paclobutrazol on GA biosynthesis, suggesting that GA deficiency is the primary cause of shb mutant phenotypes
• Thus, root meristem size in rice is modulated by SHB-mediated GA biosynthesis that regulates the elongation and proliferation of meristem cells in a developmental stage-specific manner.
• SHOEBOX Modulates Root Meristem Size in Rice through Dose-Dependent Effects of Gibberellins on Cell Elongation and Proliferation
• RLA1 was identical to the previously reported SMALL ORGAN SIZE 1 (SMOS1) which was cloned from another allele

• OsPHI-1, SMOS1~SHB~RLA1, A novel AP2-type transcription factor, SMALL ORGAN SIZE1, controls organ size downstream of an auxin signaling pathway, Among the down-regulated genes, we demonstrated by gel-shift and chromatin immunoprecipitation (ChIP) experiments that OsPHI-1, which is involved in cell expansion, is a target of SMOS1
• OsPHI-1, SMOS1~SHB~RLA1, Small Organ Size 1 and Small Organ Size 2/Dwarf and Low Tillering form a Complex to Integrate Auxin and Brassinosteroid Signaling in Rice., Consistently, the expression of OsPHI-1, a direct target of SMOS1, is up-regulated only when SMOS1 and SMOS2/DLT proteins were both present in rice cells