阿拉伯芥基因LEA4-3在鹽分逆境和離層酸反應之功能性研究

Abstract

在過去研究中，LEA蛋白家族被認為參與在像是乾旱、寒害、鹽分逆境或是離層素處理等的植物逆境反應中。阿拉伯芥第四群中的lea4-1/4-2雙突變株與lea4-5 單突變株被發現在鹽逆境處理下與野生型相較有較低的萌芽率。但是是否有其他第四群LEA也有參與在鹽逆境或是離層酸反應中還不是很清楚。此外，研究室先前發現ABF3會結合ABI5的啟動子並正向調控ABI5表現。另一方面，abf3突變株的DNA晶片微陣列的實驗結果顯示LEA4-3可能是ABF3的下游目標。為了探討在阿拉伯芥中ABF3和LEA4-3之間的轉錄關係與LEA4-3在鹽逆境和離層酸影響下的功能，本研究利用qPCR發現在鹽與離層酸處理下，abf3突變株中的LEA4-3基因表現與野生型相比有較低的趨勢。在染色質免疫沉澱實驗中，發現ABF3會與LEA4-3的啟動子結合。在離層酸處理中，lea4-3突變株與野生型相比有較低的萌芽率，且LEA4-3過量表現株在離層酸處理下主根根長與野生型相比也有較長的性狀，表示lea4-3突變株相較於野生型對於離層素較敏感。而在鹽處理中lea4-3突變株有較高的萌芽率，lea4-3突變株在鹽處理中主根根長與野生型相比也有較長的性狀，表示lea4-3突變株相較於野生型對於鹽逆境較不敏感。綜合上述結果，推斷LEA4-3參與在阿拉伯芥鹽逆境與離層酸反應中。

Late embryogenesis abundant (LEA) proteins are known to be associated with stress responses in plants, such as dehydration, cold, high salinity, or abscisic acid (ABA) treatment. A previous study showed that group four lea mutants, lea 4-1/4-2 double mutant and lea 4-5 single mutant have lower germination rate in comparison to wild type in salt stress. LEA overexpression plants show tolerant phenotypes under many abiotic stresses. However, it is unclear whether other group four LEAs function during salt stress and ABA responses. On the other hand, our microarray data show that LEA4-3 might be a candidate target of ABF3. I aim to investigate the relationship between ABF3 and LEA4-3 in the transcriptional network, and the function of LEA4-3 in salt stress and ABA responses in Arabidopsis. In the abf3 mutant, LEA gene expression is lower than wild type under salt and ABA treatment. Chromatin immunoprecipitation (ChIP) analysis results showed that ABF3 binds to the promoter of LEA4-3. Phenotypic analysis of lea4-3 mutant lines displayed lower seed germination rate than wild type in ABA treatment, and the seed germination rate of the lea4-3 mutant line was higher than wild type in salt treatment. In addition, the primary root length of LEA4-3 overexpression lines was longer than WT in ABA and salt stress condition. Taken together, these reveal that LEA4-3 may participate in ABA and salt stress response in Arabidopsis.