Department of Applied Genetics and Cell Biology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria.
Physiol Plant. 2012 Aug;145(4):527-39. doi: 10.1111/j.1399-3054.2011.01561.x. Epub 2012 Jan 31.
ARI12 belongs to a family of 'RING between RING fingers' (RBR) domain proteins with E3 ligase activity (Eisenhaber et al. 2007). The Arabidopsis genome codes for 14 ARI genes and two pseudogenes (Mladek et al. 2003). Under standard growth conditions ARI12 is predominantly expressed in roots. In addition, ARI12 is strongly induced in leaves following exposure to ultraviolet (UV)-B radiation at dosages similar to those in areas under a reduced ozone layer. With quantitative reverse transcription polymerase chain reaction analyses and promoter:reporter constructs we show that the expression of ARI12 peaks 2-4 h after UV-B radiation exposure. To test if ARI12's transcriptional activation depends on key players of the UV-B signaling pathway, ARI12 expression was quantified in mutants of the ELONGATED HYPOCOTYL5 (HY5), HY5 HOMOLOG (HYH) and the UV RESISTANCE LOCUS8 (UVR8) genes. ARI12 transcription was reduced by 50-70% in hy5, hyh and hy5/hyh double mutants, but not in uvr8 mutants. However, under low fluence rate UV-B conditions ARI12 is not induced in these mutants. Our results show that ARI12 represents a downstream target of the low fluence rate UVR8/HY5/HYH UV-B signaling pathway while under high fluence rates its expression is regulated by the two bZIP transcription factors HY5 and HYH in an UVR8-independent manner.
ARI12 属于具有 E3 连接酶活性的“环指之间的 RING”（RBR）结构域蛋白家族（Eisenhaber 等人，2007 年）。拟南芥基因组编码 14 个 ARI 基因和两个假基因（Mladek 等人，2003 年）。在标准生长条件下，ARI12 主要在根中表达。此外，在叶片中，当暴露于类似于臭氧层减少区域的紫外线（UV）-B 辐射剂量时，ARI12 强烈诱导。通过定量逆转录聚合酶链反应分析和启动子：报告构建体，我们表明 ARI12 的表达在 UV-B 辐射暴露后 2-4 小时达到峰值。为了测试 ARI12 的转录激活是否依赖于 UV-B 信号通路的关键参与者，我们在 ELONGATED HYPOCOTYL5 (HY5)、HY5 HOMOLOG (HYH) 和 UV RESISTANCE LOCUS8 (UVR8) 基因突变体中定量了 ARI12 的表达。在 hy5、hyh 和 hy5/hyh 双突变体中，ARI12 的转录减少了 50-70%，但在 uvr8 突变体中没有。然而，在低通量率 UV-B 条件下，这些突变体中不会诱导 ARI12。我们的结果表明，ARI12 是低通量率 UVR8/HY5/HYH UV-B 信号通路的下游靶标，而在高通量率下，其表达由两个 bZIP 转录因子 HY5 和 HYH 以 UVR8 独立的方式调节。
