Gao Hongbo, Brandizzi Federica, Benning Christoph, Larkin Robert M
Michigan State University-Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA.
Proc Natl Acad Sci U S A. 2008 Oct 21;105(42):16398-403. doi: 10.1073/pnas.0808463105. Epub 2008 Oct 10.
In plants, heat stress responses are controlled by heat stress transcription factors that are conserved among all eukaryotes and can be constitutively expressed or induced by heat. Heat-inducible transcription factors that are distinct from the "classical" heat stress transcription factors have also been reported to contribute to heat tolerance. Here, we show that bZIP28, a gene encoding a putative membrane-tethered transcription factor, is up-regulated in response to heat and that a bZIP28 null mutant has a striking heat-sensitive phenotype. The heat-inducible expression of genes that encode BiP2, an endoplasmic reticulum (ER) chaperone, and HSP26.5-P, a small heat shock protein, is attenuated in the bZIP28 null mutant. An estradiol-inducible bZIP28 transgene induces a variety of heat and ER stress-inducible genes. Moreover, heat stress appears to induce the proteolytic release of the predicted transcription factor domain of bZIP28 from the ER membrane, thereby causing its redistribution to the nucleus. These findings indicate that bZIP28 is an essential component of a membrane-tethered transcription factor-based signaling pathway that contributes to heat tolerance.
在植物中，热应激反应由热应激转录因子控制，这些转录因子在所有真核生物中都是保守的，并且可以组成型表达或由热诱导表达。据报道，与“经典”热应激转录因子不同的热诱导转录因子也有助于耐热性。在这里，我们表明，bZIP28是一个编码假定的膜结合转录因子的基因，它在热应激下上调，并且bZIP28基因敲除突变体具有显著的热敏感表型。编码内质网（ER）伴侣BiP2和小热休克蛋白HSP26.5-P的基因的热诱导表达在bZIP28基因敲除突变体中减弱。一种雌激素诱导的bZIP28转基因可诱导多种热应激和内质网应激诱导基因。此外，热应激似乎诱导bZIP28预测的转录因子结构域从内质网膜上进行蛋白水解释放，从而导致其重新分布到细胞核。这些发现表明，bZIP28是基于膜结合转录因子的信号通路的一个重要组成部分，有助于耐热性。
