Gamboa-Meléndez Heber, Huerta Apolonio I, Judelson Howard S
Department of Plant Pathology and Microbiology, University of California, Riverside, California, USA.
Eukaryot Cell. 2013 Oct;12(10):1403-12. doi: 10.1128/EC.00141-13. Epub 2013 Aug 23.
Transcription factors of the basic leucine zipper (bZIP) family control development and stress responses in eukaryotes. To date, only one bZIP has been described in any oomycete; oomycetes are members of the stramenopile kingdom. In this study, we describe the identification of 38 bZIPs from the Phytophthora infestans genome. Half contain novel substitutions in the DNA-binding domain at a site that in other eukaryotes is reported to always be Asn. Interspecific comparisons indicated that the novel substitutions (usually Cys, but also Val and Tyr) arose after oomycetes diverged from other stramenopiles. About two-thirds of P. infestans bZIPs show dynamic changes in mRNA levels during the life cycle, with many of the genes being upregulated in sporangia, zoospores, or germinated zoospore cysts. One bZIP with the novel Cys substitution was shown to reside in the nucleus throughout growth and development. Using stable gene silencing, the functions of eight bZIPs with the Cys substitution were tested. All but one were found to play roles in protecting P. infestans from hydrogen peroxide-induced injury, and it is proposed that the novel Cys substitution serves as a redox sensor. A ninth bZIP lacking the novel Asn-to-Cys substitution, but having Cys nearby, was also shown through silencing to contribute to defense against peroxide. Little effect on asexual development, plant pathogenesis, or resistance to osmotic stress was observed in transformants silenced for any of the nine bZIPs.
碱性亮氨酸拉链（bZIP）家族的转录因子控制真核生物的发育和应激反应。迄今为止，在任何卵菌纲中仅描述了一种bZIP；卵菌纲是不等鞭毛菌界的成员。在本研究中，我们描述了从致病疫霉基因组中鉴定出38个bZIP。其中一半在DNA结合结构域的一个位点含有新的取代，在其他真核生物中该位点据报道总是天冬酰胺。种间比较表明，新的取代（通常是半胱氨酸，但也有缬氨酸和酪氨酸）是在卵菌纲与其他不等鞭毛菌分化之后出现的。大约三分之二的致病疫霉bZIP在生命周期中mRNA水平呈现动态变化，许多基因在孢子囊、游动孢子或萌发的游动孢子囊中上调。一个具有新的半胱氨酸取代的bZIP在整个生长发育过程中都定位于细胞核。利用稳定的基因沉默技术，测试了8个具有半胱氨酸取代的bZIP的功能。发现除一个之外的所有bZIP在保护致病疫霉免受过氧化氢诱导的损伤中发挥作用，并且有人提出新的半胱氨酸取代作为一种氧化还原传感器。通过沉默还表明，第九个缺乏新的天冬酰胺到半胱氨酸取代但附近有半胱氨酸的bZIP有助于抵御过氧化物。在沉默了这9个bZIP中任何一个的转化体中，未观察到对无性发育、植物致病性或渗透胁迫抗性有显著影响。
