Functional analysis of a rice importin-α binding protein

为了寻找参与植物对光环境响应的新型核蛋白，作者分析了一种候选蛋白IABP4的功能，该蛋白通过与水稻进口蛋白α1a（IMPα1a）结合而被分离出来，IMPα1a是核转运机制的一个组成部分，在黑暗中表达强烈，在光照下表达下调。得到的结果如下：1。基因表达及光照影响：与水稻IMPα1a基因相似，IABP4在水稻和拟南芥黄化苗和绿苗中均受光照下调表达。结果表明，由于IABP4蛋白水平降低以及IAB P4.2的核输入减少，IABP4的核积累可能在黑暗中减少。敲除系功能分析：在拟南芥中鉴定出5个IABP4敲除系，在黑暗环境中敲除的IABP4开钩和子叶的比例高于野生型，提示IABP4蛋白可能抑制了黑暗环境下的光形态发生。由于萌发的幼苗在T-DNA插入方面都是杂合子，因此纯合子被认为是胚胎致死性的或不能发芽的，这表明IABP4不仅参与光形态发生的控制，而且对植物也是必不可少的。瘤内定位和光的影响：虽然我们获得了IABP4抗血清，但它含有对其他植物蛋白的抗体，因此我们不能将其用于定位研究。目前迫切需要通过纯化抗体或gfp融合检测IABP4的核定位。

To identify novel nuclear proteins that are involved in plants' responses to light environment, the author analyzed the function of a candidate protein, named IABP4, that had been isolated by its binding to rice importin-α1a(IMPα1a), a component of nuclear transport machinery, whose expression is strong in the dark and is down-regulated by light. The obtained results are as follows.1.Gene expression and the effect of light : Similar to rice IMPα1a gene, the expression of IABP4 was down-regulated by light both in etiolated-and green-seedlings of rice and Arabidopsis. The result suggests that nuclear accumulation of IABP4 might be reduced in the dark as a result of reduced IABP4 protein level as well as reduced nuclear import of IAB P4.2.Functional analysis by knockout lines : Five knockout lines of IABP4 were identified in Arabidopsis, and the proportion of seedlings with open hook and cotyledons in the dark was higher in the knockouts than in wild type, suggesting that IABP4 protein may be suppressing photomorphogenesis in the dank. Because germinated seedlings were all hetero-zygous with respect to T-DNA insertion, the homozygote is considered to be embryonic lethal or unable to germinate, suggesting that IABP4 is not only involved in the control of photomorphgenesis but also essential for plants.3.IntraceMar localization and the effect of light: Though we obtained IABP4 antiserum, it contained antibodies to other plant proteins, so we could not use it for localization studies. By purifying antibody or by using GFP-fusion, examination of nuclear localization of IABP4 is urgently required.