Medical and Biotechnological Application Division, Japan Atomic Energy Agency, Takasaki 370-1292, Japan.
Plant Physiol. 2012 Sep;160(1):93-105. doi: 10.1104/pp.111.188409. Epub 2012 May 10.
Previously, a dysfunction of the SMALL ACIDIC PROTEIN1 (SMAP1) gene was identified as the cause of the anti-auxin resistant1 (aar1) mutant of Arabidopsis (Arabidopsis thaliana). SMAP1 is involved in the response pathway of synthetic auxin, 2,4-dichlorophenoxyacetic acid, and functions upstream of the auxin/indole-3-acetic acid protein degradation step in auxin signaling. However, the exact mechanism by which SMAP1 functions in auxin signaling remains unknown. Here, we demonstrate that SMAP1 is required for normal plant growth and development and the root response to indole-3-acetic acid or methyl jasmonate in the auxin resistant1 (axr1) mutation background. Deletion analysis and green fluorescent protein/glutathione S-transferase pull-down assays showed that SMAP1 physically interacts with the CONSTITUTIVE PHOTOMORPHOGENIC9 SIGNALOSOME (CSN) via the SMAP1 F/D region. The extremely dwarf phenotype of the 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-regulated signaling processes via its interaction with components associated with RELATED TO UBIQUITIN modification.
先前，SMALL ACIDIC PROTEIN1（SMAP1）基因的功能障碍被确定为拟南芥（Arabidopsis thaliana）抗生长素抗性 1（aar1）突变体的原因。SMAP1 参与合成生长素、2,4-二氯苯氧乙酸的反应途径，并在生长素信号转导中生长素/吲哚-3-乙酸蛋白降解步骤的上游发挥作用。然而，SMAP1 在生长素信号转导中发挥作用的确切机制尚不清楚。在这里，我们证明 SMAP1 是正常植物生长和发育以及在生长素抗性 1（axr1）突变背景下根对吲哚-3-乙酸或茉莉酸甲酯的反应所必需的。缺失分析和绿色荧光蛋白/谷胱甘肽 S-转移酶下拉测定表明，SMAP1 通过 SMAP1 F/D 区域与组成型光形态发生 9 信号小体（CSN）发生物理相互作用。aar1-1 csn5a-1 双突变体的极矮表型证实了 SMAP1 在有限的 CSN 功能下参与植物生长和发育的功能作用。我们的研究结果表明，SMAP1 通过与 RELATED TO UBIQUITIN 修饰相关的成分相互作用，参与生长素反应，并可能参与其他 Cullin-RING 泛素连接酶调节的信号转导过程。
