Nakasone A, Fujiwara M, Fukao Y, Biswas KK, Rahman A, Kawai-Yamada M, Narumi I, Uchimiya H, Oono Y

Previously, a dysfunction of the SMALL ACIDIC PROTEIN 1 (SMAP1) gene was identified as the cause of the antiauxin resistant 1 (aar1) mutant of Arabidopsis. SMAP1 is involved in the response pathway of synthetic auxin, 2,4-dichlorophenoxyacetic acid (2,4-D), and functions upstream of the AUXIN (AUX)/INDOLE-3-ACETIC ACID (IAA)-proteins degradation step in ...

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auxin signaling. However, the exact mechanism by which SMAP1 functions in auxin signaling remains unknown. Here, we demonstrated that SMAP1 is required for normal plant growth and development, and roots response to IAA or methyl jasmonate in the auxin resistant 1 (axr1) mutation background. Deletion analysis and green fluorescent protein (GFP) / glutathione S-transferase (GST) pull-down assays showed that SMAP1 physically interacts with the CONSTITUTIVE PHOTOMORPHOGENIC-9 SIGNALOSOME (CSN) via the SMAP1 F/D-region. The extremely dwarf phenotype of aar1-1 csn5a-1 double mutant confirms the functional role of SMAP1 in plant growth and development under limiting CSN functionality. Our findings suggest that SMAP1 is involved in the auxin response and possibly in other cullin-RING ubiquitin ligase (CRL)-regulated signaling processes via its interaction with components associated with related-to-ubiquitin (RUB) modification.

Date: May. 10, 2012

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