Loose Plant Architecture1 (LPA1) determines lamina joint bending by suppressing auxin signalling that interacts with C-22-hydroxylated and 6-deoxo brassinosteroids in rice

Lamina inclination is a key agronomical character that determines plant architecture and is sensitive to auxin and brassinosteroids (BRs). Loose Plant Architecture1 (LPA1) in rice (Oryza sativa) and its Arabidopsis homologues (SGR5/AtIDD15) have been reported to control plant architecture and auxin...

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Published in:Journal of experimental botany 2016-03, Vol.67 (6), p.1883-1895
Main Authors: Liu, Jing Miao, Park, Soon Ju, Huang, Jin, Lee, Eun Jin, Xuan, Yuan Hu, Je, Byoung Il, Kumar, Vikranth, Priatama, Ryza A., Raj K, Vimal, Kim, Sung Hoon, Min, Myung Ki, Cho, Jun Hyeon, Kim, Tae Ho, Chandran, Anil Kumar Nalini, Jung, Ki Hong, Takatsuto, Suguru, Fujioka, Shozo, Han, Chang-deok
Format: Article
Language:English
Subjects:
Alleles
Biomechanical Phenomena - drug effects
Brassinosteroids - pharmacology
Gene Expression Regulation, Plant - drug effects
Genes, Plant
Hydroxylation
Indoleacetic Acids - metabolism
Mutation - genetics
Oryza - drug effects
Oryza - genetics
Oryza - physiology
Phenotype
Plant Epidermis - cytology
Plant Epidermis - drug effects
Plant Leaves - drug effects
Plant Leaves - physiology
Plant Proteins - metabolism
Real-Time Polymerase Chain Reaction
RESEARCH PAPER
Signal Transduction - drug effects
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Summary:Lamina inclination is a key agronomical character that determines plant architecture and is sensitive to auxin and brassinosteroids (BRs). Loose Plant Architecture1 (LPA1) in rice (Oryza sativa) and its Arabidopsis homologues (SGR5/AtIDD15) have been reported to control plant architecture and auxin homeostasis. This study explores the role of LPA1 in determining lamina inclination in rice. LPA1 acts as a positive regulator to suppress lamina bending. Genetic and biochemical data indicate that LPA1 suppresses the auxin signalling that interacts with C-22-hydroxylated and 6-deoxo BRs, which regulates lamina inclination independently of OsBRI1. Mutant lpa1 plants are hypersensitive to indole-3-acetic acid (IAA) during the lamina inclination response, which is suppressed by the brassinazole (Brz) inhibitor of C-22 hydroxylase involved in BR synthesis. A strong synergic effect is detected between lpa1 and d2 (the defective mutant for catalysis of C-23-hydroxylated BRs) during IAA-mediated lamina inclination. No significant interaction between LPA1 and OsBRI1 was identified. The lpa1 mutant is sensitive to C-22-hydroxylated and 6-deoxo BRs in the d61-1 (rice BRI1 mutant) background. We present evidence verifying that two independent pathways function via either BRs or BRI1 to determine IAA-mediated lamina inclination in rice. RNA sequencing analysis and qRT-PCR indicate that LPA1 influences the expression of three OsPIN genes (OsPIN1a, OsPIN1c and OsPIN3a), which suggests that auxin flux might be an important factor in LPA1-mediated lamina inclination in rice.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/erw002