Department of Biology, Heinrich Heine University Düsseldorf, Germany.
Front Plant Sci. 2013 Jul 15;4:252. doi: 10.3389/fpls.2013.00252. eCollection 2013.
Genome-wide microarray analyses revealed that during biological activation of systemic acquired resistance (SAR) in Arabidopsis, the transcript levels of several hundred plant genes were consistently up- (SAR(+) genes) or down-regulated (SAR(-) genes) in systemic, non-inoculated leaf tissue. This transcriptional reprogramming fully depended on the SAR regulator FLAVIN-DEPENDENT MONOOXYGENASE1 (FMO1). Functional gene categorization showed that genes associated with salicylic acid (SA)-associated defenses, signal transduction, transport, and the secretory machinery are overrepresented in the group of SAR(+) genes, and that the group of SAR(-) genes is enriched in genes activated via the jasmonate (JA)/ethylene (ET)-defense pathway, as well as in genes associated with cell wall remodeling and biosynthesis of constitutively produced secondary metabolites. This suggests that SAR-induced plants reallocate part of their physiological activity from vegetative growth towards SA-related defense activation. Alignment of the SAR expression data with other microarray information allowed us to define three clusters of SAR(+) genes. Cluster I consists of genes tightly regulated by SA. Cluster II genes can be expressed independently of SA, and this group is moderately enriched in H2O2- and abscisic acid (ABA)-responsive genes. The expression of the cluster III SAR(+) genes is partly SA-dependent. We propose that SA-independent signaling events in early stages of SAR activation enable the biosynthesis of SA and thus initiate SA-dependent SAR signaling. Both SA-independent and SA-dependent events tightly co-operate to realize SAR. SAR(+) genes function in the establishment of diverse resistance layers, in the direct execution of resistance against different (hemi-)biotrophic pathogen types, in suppression of the JA- and ABA-signaling pathways, in redox homeostasis, and in the containment of defense response activation. Our data further indicated that SAR-associated defense priming can be realized by partial pre-activation of particular defense pathways.
全基因组微阵列分析显示，在拟南芥系统获得性抗性（SAR）的生物学激活过程中，数百个植物基因的转录水平在系统的、未接种的叶片组织中持续上调（SAR(+)基因）或下调（SAR(-)基因）。这种转录重编程完全依赖于 SAR 调节因子黄素依赖单加氧酶 1（FMO1）。功能基因分类表明，与水杨酸（SA）相关防御、信号转导、运输和分泌机制相关的基因在 SAR(+)基因中过度表达，而 SAR(-)基因富集了通过茉莉酸（JA）/乙烯（ET）防御途径激活的基因，以及与细胞壁重塑和组成型产生的次生代谢物生物合成相关的基因。这表明，SAR 诱导的植物将其部分生理活动从营养生长重新分配到与 SA 相关的防御激活。将 SAR 表达数据与其他微阵列信息进行比对，使我们能够定义 SAR(+)基因的三个簇。簇 I 由 SA 严格调控的基因组成。簇 II 基因可以独立于 SA 表达，该组中等程度富集 H2O2 和脱落酸（ABA）响应基因。簇 III SAR(+)基因的表达部分依赖于 SA。我们提出，SAR 激活早期的 SA 非依赖性信号事件使 SA 的生物合成成为可能，从而启动依赖于 SA 的 SAR 信号转导。SA 非依赖性和 SA 依赖性事件紧密合作以实现 SAR。SAR(+)基因在建立多种抗性层、直接执行对不同（半）生物病原体类型的抗性、抑制 JA 和 ABA 信号通路、维持氧化还原稳态以及控制防御反应激活方面发挥作用。我们的数据进一步表明，SAR 相关防御的启动可以通过部分预先激活特定的防御途径来实现。
