植物抗铝毒转录因子STOP1/ART1蛋白降解机制的解析

Aluminum (Al) toxicity is a major limiting factor for crop production on acid soils. Some plants have evolved resistance mechanisms to Al toxicity. Arabidopsis secretes malate through the AtALMT1 transporter to chelate and detoxify Al. AtALMT1 expression is induced by Al stress and controlled by STOP1, an Al-resistance transcription factor. However, the induction of AtALMT1 by Al cannot be explained by the mRNA expression level of STOP1 because STOP1 expression is not affected by Al. Through a forward genetic screen, we identified a mutant tra1 where the expression of AtALMT1 was increased. We cloned the TRA1 gene and preliminarily proved that TRA1 might be involved in the regulation of the stability of STOP1. Next, we will perform additional experiments including the in vitro and in vivo interactions between TRA1 and STOP1, STOP1 protein accumulation in the tra1 mutant, and other genetic, physiological and molecular work to further determine the role of TRA1 in the regulation of STOP1 protein degradation and AtALMT1 expression. Furthermore, there were two homologous genes of TRA1 in rice, and we also found that one of the TRA1 homologs was able to interact with the Al-resistance transcription factor ART1. Therefore, we are also going to perform functional analysis of TRA1 homologs and determine their important roles in the detoxification of Al in rice.

铝毒是酸性土壤中作物生产的主要限制因子。一些植物进化了抗铝毒机制，拟南芥主要通过转运蛋白AtALMT1分泌苹果酸到根际与铝螯合和解除毒害。AtALMT1的表达受铝毒诱导并受关键抗铝毒转录因子STOP1的调控，但是STOP1的mRNA表达变化并不能解释AtALMT1的表达受铝毒诱导。通过正向遗传筛选，我们获得一个使AtALMT1基因表达升高的突变体tra1。我们克隆了TRA1基因，并初步证明TRA1可能参与调控STOP1的稳定性。下一步我们将在蛋白互作、蛋白表达以及遗传、生理和相关分子生物学实验上进一步验证TRA1通过控制STOP1稳定性来调控AtALMT1表达的机制。此外，水稻中有两个TRA1同源基因，我们也初步证明了其中一个TRA1同源基因能够与水稻抗铝毒转录因子ART1相互作用，因而我们也将对水稻中的TRA1同源基因进行功能解析，阐明其在水稻抗铝毒方面的重要作用。

铝毒是酸性土壤中作物生产的主要限制因子。一些植物进化了抗铝毒机制，拟南芥主要通过转运蛋白AtALMT1分泌苹果酸到根际与铝螯合和解除毒害。锌指转录因子STOP1在抗铝毒过程中扮演关键角色，它主要通过调控包括AtALMT1基因在内的表达介导对铝毒的抗性。虽然AtALMT1等STOP1下游基因表达受铝毒诱导，但是STOP1的mRNA表达不受铝毒影响，因而STOP1可能受到转录后调控。我们构建了AtALMT1启动子融合LUC报告基因表达的株系，通过筛选LUC荧光改变的突变体来克隆和解析调控STOP1的新组分。我们获得了一个使LUC报告基因和AtALMT1表达升高的突变体rae1 (regulation of AtALMT1 expression 1)。采用全基因组测序结合标记连锁分析，我们克隆了RAE1基因，发现它编码一个F-box蛋白。通过一系列的生理、生化和遗传实验，我们阐明了RAE1与抗铝毒转录因子STOP1互作并促进其泛素化和降解从而调控抗铝毒的机制。此外，通过对RAE1同源基因的功能解析，我们发现植物中RAE1的直系和旁系同源蛋白在调控抗铝毒转录因子STOP1/ART1蛋白稳定性上的功能是保守的。但是，RAE1直系同源蛋白在调控植物抗铝毒方面起更重要的角色。进一步发现STOP1蛋白的高积累负调控植物生长，因此在利用STOP1/ART1提高作物抗铝毒时需防止其表达过高抑制作物的生长。我们的研究结果不仅揭示了RAE1同源蛋白通过调控抗铝毒转录因子STOP1/ART1稳定性从而调控植物抗铝毒的新机制，而且为改良作物抗铝毒能力提供了关键的靶标基因。