Previously, we found that Arabidopsis plants transformed with a construct containing the promoter of Oshsp17.3 from rice fused to the β-glucuronidase gene (GUS), Oshsp17.3Pro::GUS (Oshsp17.3p), showed a GUS signal after heat shock (HS) or azetidine-2-carboxylic acid (AZC) treatment. HS and AZC trigger the heat shock response (HSR) and cytosolic protein response (CPR), respectively, in the cytosol by modulating specific heat shock factor (HSF) activity. Here we further identified that AtHSFA2 (At2g26150), AtHSFA7a (At3g51910), AtHSFB2a (At5g62020), and AtHSFB2b (At4g11660) are HS- and AZC-inducible; AtHSFA4a (At4g18880) is AZC-inducible; and AtHSFA5 (At4g13980) is less AZC- and HS-inducible. To investigate the roles of these 6 AtHSFs in the HSR or CPR, we crossed two independent Oshsp17.3p transgenic Arabidopsis plants with the AtHSF-knockout mutants athsfa2 (SALK_008978), athsfa4a (GABI_181H12), athsfa5 (SALK_004385), athsfa7a (SALK_080138), athsfb2a (SALK_137766), and athsfb2b (SALK_047291), respectively. As compared with the wild type, loss-of-function mutation of AtHSFA2, AtHSFA4a, and AtHSFA7a decreased HS and AZC responsiveness, so these 3 AtHSFs are essential for the HSR and CPR. In addition, loss-of-function results indicated that AthsfB2b is involved in regulating the HSR in Arabidopsis. Furthermore, analysis of the relative GUS activity of two double knockout mutants, athsfA2/athsfA4a and athsfA2/athsfA7a, revealed that AtHSFA2, AtHSFA4a, and AtHSFA7a function differentially in the HSR and CPR. Transcription profiling in athsf mutants revealed positive or negative transcriptional regulation among the 6 AtHSFs in Arabidopsis plants under HS and AZC conditions. Tunicamycin treatment demonstrated that these 6 AtHSFs are not involved in the unfolded protein response.

中文翻译：

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拟南芥HSFA2，HSFA4a和HSFA7a在热休克反应和胞质蛋白反应中的作用。

以前，我们发现，用含有融合了β-葡萄糖醛酸苷酶基因（GUS），Oshsp17.3Pro :: GUS（Oshsp17.3p）的水稻中Oshsp17.3启动子的构建体转化的拟南芥植物在热激后显示出GUS信号。 （HS）或氮杂环丁烷-2-羧酸（AZC）处理。HS和AZC通过调节特定的热激因子（HSF）活性，分别在细胞质中触发热激反应（HSR）和胞质蛋白反应（CPR）。在这里，我们进一步确定AtHSFA2（At2g26150），AtHSFA7a（At3g51910），AtHSFB2a（At5g62020）和AtHSFB2b（At4g11660）是HS和AZC诱导的。AtHSFA4a（At4g18880）是AZC诱导的；而AtHSFA5（At4g13980）的AZC和HS诱导性较低。为了研究这6个AtHSF在HSR或CPR中的作用，我们跨越了两个独立的Oshsp17。具有AtHSF基因敲除突变体assfa2（SALK_008978），assfa4a（GABI_181H12），assfa5（SALK_004385），assfa7a（SALK_080138），athsfb2a（SALK_137766）和a047的3p转基因拟南芥植物。与野生型相比，AtHSFA2，AtHSFA4a和AtHSFA7a的功能丧失突变降低了HS和AZC反应性，因此这3个AtHSF对HSR和CPR是必不可少的。另外，功能丧失的结果表明AthsfB2b参与了拟南芥中HSR的调节。此外，对两个双敲除突变体athsfA2 / athsfA4a和athsfA2 / athsfA7a的相对GUS活性的分析表明，AtHSFA2，AtHSFA4a和AtHSFA7a在HSR和CPR中的功能有所不同。Athsf突变体中的转录谱显示，在HS和AZC条件下，拟南芥植物的6个AtHSF中有正转录或负转录调节。衣霉素处理表明这6个AtHSF不参与未折叠的蛋白质反应。