Goritschnig Sandra, Weihmann Tabea, Zhang Yuelin, Fobert Pierre, McCourt Peter, Li Xin
Michael Smith Laboratories , University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
Plant Physiol. 2008 Sep;148(1):348-57. doi: 10.1104/pp.108.117663. Epub 2008 Jul 3.
Plants utilize tightly regulated mechanisms to defend themselves against pathogens. Initial recognition results in activation of specific Resistance (R) proteins that trigger downstream immune responses, in which the signaling networks remain largely unknown. A point mutation in SUPPRESSOR OF NPR1 CONSTITUTIVE1 (SNC1), a RESISTANCE TO PERONOSPORA PARASITICA4 R gene homolog, renders plants constitutively resistant to virulent pathogens. Genetic suppressors of snc1 may carry mutations in genes encoding novel signaling components downstream of activated R proteins. One such suppressor was identified as a novel loss-of-function allele of ENHANCED RESPONSE TO ABSCISIC ACID1 (ERA1), which encodes the beta-subunit of protein farnesyltransferase. Protein farnesylation involves attachment of C15-prenyl residues to the carboxyl termini of specific target proteins. Mutant era1 plants display enhanced susceptibility to virulent bacterial and oomycete pathogens, implying a role for farnesylation in basal defense. In addition to its role in snc1-mediated resistance, era1 affects several other R-protein-mediated resistance responses against bacteria and oomycetes. ERA1 acts partly independent of abscisic acid and additively with the resistance regulator NON-EXPRESSOR OF PR GENES1 in the signaling network. Defects in geranylgeranyl transferase I, a protein modification similar to farnesylation, do not affect resistance responses, indicating that farnesylation is most likely specifically required in plant defense signaling. Taken together, we present a novel role for farnesyltransferase in plant-pathogen interactions, suggesting the importance of protein farnesylation, which contributes to the specificity and efficacy of signal transduction events.
植物利用严格调控的机制来抵御病原体。初始识别会激活特定的抗性（R）蛋白，从而触发下游免疫反应，而其中的信号网络在很大程度上仍不为人知。寄生霜霉抗性4 R基因同源物NPR1组成型表达抑制因子1（SNC1）中的一个点突变，使植物对毒性病原体具有组成型抗性。snc1的遗传抑制子可能在编码激活的R蛋白下游新型信号成分的基因中携带突变。其中一个这样的抑制子被鉴定为脱落酸增强反应1（ERA1）的一个新的功能缺失等位基因，ERA1编码蛋白质法尼基转移酶的β亚基。蛋白质法尼基化涉及将C15异戊二烯基残基连接到特定靶蛋白的羧基末端。突变的era1植物对毒性细菌和卵菌病原体表现出增强的易感性，这意味着法尼基化在基础防御中发挥作用。除了在snc1介导的抗性中发挥作用外，era1还影响其他几种R蛋白介导的针对细菌和卵菌的抗性反应。ERA1在信号网络中部分独立于脱落酸起作用，并与病程相关基因非表达子1（NPR1）协同发挥作用。香叶基香叶基转移酶I（一种类似于法尼基化的蛋白质修饰）的缺陷不影响抗性反应，这表明法尼基化很可能在植物防御信号传导中具有特异性需求。综上所述，我们揭示了法尼基转移酶在植物 - 病原体相互作用中的新作用，表明蛋白质法尼基化的重要性，它有助于信号转导事件的特异性和有效性。
