To investigate essential components mediating stress signaling in plants, we initiated a large-scale stress response screen using Arabidopsis plants carrying the firefly luciferase reporter gene under the control of the stress-responsive RD29A promoter. Here we report the identification and characterization of a mutant, hos9-1 (for high expression of osmotically responsive genes), in which the reporter construct was hyperactivated by low temperature, but not by abscisic acid or salinity stress. The mutants grow more slowly, and flower later, than do wild-type plants and are more sensitive to freezing, both before and after acclimation, than the wild-type plants. The HOS9 gene encodes a putative homeodomain transcription factor that is localized to the nucleus. HOS9 is constitutively expressed and not further induced by cold stress. Cold treatment increased the level of transcripts of the endogenous RD29A, and some other stress-responsive genes, to a higher level in hos9-1 than in wild-type plants. However, the C repeat/dehydration responsive element-binding factor (CBF) transcription factor genes that mediate a part of cold acclimation in Arabidopsis did not have their response to cold altered by the hos9-1 mutation. Correspondingly, microarray analysis showed that none of the genes affected by the hos9-1 mutation are controlled by the CBF family. Together, these results suggest that HOS9 is important for plant growth and development, and for a part of freezing tolerance, by affecting the activity of genes independent of the CBF pathway.

译文

:为了研究介导植物中压力信号转导的基本成分,我们启动了使用拟南芥植物的大规模胁迫反应筛选,该植物携带萤火虫荧光素酶报道基因,处于应激反应性RD29A启动子的控制之下。在这里,我们报告鉴定和表征的突变体hos9-1(用于高表达渗透反应基因),其中报告基因构建体通过低温而不是脱落酸或盐分胁迫而过度活化。与野生型植物相比,突变体的生长速度更慢,并且开花较晚,并且在适应之前和之后,突变体比野生型植物对冻结更敏感。 HOS9基因编码位于细胞核中的一个假定的同源域转录因子。 HOS9是组成型表达的,不会被冷胁迫进一步诱导。寒冷处理使hos9-1中的内源RD29A和其他一些胁迫响应基因的转录本水平高于野生型植物。但是,介导拟南芥部分冷驯化的C重复/脱水反应元件结合因子(CBF)转录因子基因没有因hos9-1突变而改变其对寒冷的反应。相应地,微阵列分析表明,受hos9-1突变影响的基因均不受CBF家族的控制。总之,这些结果表明,HOS9通过影响独立于CBF途径的基因的活性,对于植物生长和发育以及部分抗冻性很重要。

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