NAI2 Is an Endoplasmic Reticulum Body Component That Enables ER Body Formation in Arabidopsis thaliana
NAI2 Is an Endoplasmic Reticulum Body Component That Enables ER Body Formation in Arabidopsis thaliana
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DOI：
10.1105/tpc.108.059345
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发表时间：
2008-09-01
期刊：
影响因子：
11.6
通讯作者：
Nishimura, Mikio
中科院分区：
文献类型：
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作者：
Yamada, Kenji;Nagano, Atsushi J.;Nishimura, Mikio
植物发育各种内质网(ER)衍生结构，每种结构都有特定的功能。在拟南芥中发现的内质网小体是一个纺锤形的结构，它特异性地积累高水平的PYK10/BGLU23，这是一种承载内质网保留信号的β-葡萄糖苷酶。内质网小体形成的分子机制尚不清楚。我们在拟南芥幼苗中分离到一个内质网身体缺陷突变体，我们将其命名为NAI2。NAI2基因(At3g15950)编码一个仅存在于十字花科植物中的独特蛋白质家族的成员。NAI2定位于内质网小体，NAI2基因表达的降低延长了内质网小体，减少了它们的数量。NAI2缺乏并不影响PYK10的mRNA水平，但降低了PYK10蛋白的水平，使其在内质网中均匀扩散。NAI1是负责内质网小体形成的转录因子，调节NAI2基因的表达。这些结果表明，NAI2是使拟南芥内质网小体形成和PYK10在内质网体内积累的关键因子。有趣的是，内质网体样结构也仅限于十字花目，包括十字花科。NAI2同源物可能是为了产生内质网体样结构而在油菜目中特异进化的。
Plants develop various endoplasmic reticulum (ER)-derived structures, each of which has specific functions. The ER body found in Arabidopsis thaliana is a spindle-shaped structure that specifically accumulates high levels of PYK10/BGLU23, a beta-glucosidase that bears an ER-retention signal. The molecular mechanisms underlying the formation of the ER body remain obscure. We isolated an ER body-deficient mutant in Arabidopsis seedlings that we termed nai2. The NAI2 gene (At3g15950) encodes a member of a unique protein family that is only found in the Brassicaceae. NAI2 localizes to the ER body, and a reduction in NAI2 gene expression elongates ER bodies and reduces their numbers. NAI2 deficiency does not affect PYK10 mRNA levels but reduces the level of PYK10 protein, which becomes uniformly diffused throughout the ER. NAI1, a transcription factor responsible for ER body formation, regulates NAI2 gene expression. These observations indicate that NAI2 is a key factor that enables ER body formation and the accumulation of PYK10 in ER bodies of Arabidopsis. Interestingly, ER body-like structures are also restricted to the Brassicales, including the Brassicaceae. NAI2 homologs may have evolved specifically in Brassicales for the purpose of producing ER body-like structures.