避荫综合症（SAS）出现在竞争光的密集生长的植物中。在拟南芥中，植物色素相互作用因子（PIF）蛋白通过生长素的产生将阴影的感知与茎伸长联系起来。这里,我们报道PIF抑制遮荫诱导的AUXIN反应因子18（ARF18）的表达，ARF18抑制生长素信号。因此,PIF介导的ARF18抑制在模拟阴影中增强生长素依赖性下胚轴伸长。此外，我们发现PIF和ARF18都直接抑制qua-quine淀粉（QQS），控制碳和氮的分配。阴影抑制的QQS减弱了淀粉向蛋白质的转化，从而减少了叶面积。我们的结果表明，PIF依赖性基因调控协调多个SAS反应，包括通过ARF18改变茎生长，以及通过QQS改变叶片生长和代谢。
Shade avoidance syndrome (SAS) arises in densely growing plants that compete for light. In Arabidopsis thaliana, phytochrome interacting factor (PIF) proteins link the perception of shade to stem elongation via auxin production. Here, we report that PIFs inhibit the shade-induced expression of AUXIN RESPONSE FACTOR 18 (ARF18), and ARF18 represses auxin signaling. Therefore, PIF-mediated inhibition of ARF18 enhances auxin-dependent hypocotyl elongation in simulated shade. Furthermore, we show that both PIFs and ARF18 directly repress qua-quine starch (QQS), which controls the allocation of carbon and nitrogen. Shade-repressed QQS attenuates the conversion of starch to protein and thus reduced leaf area. Our results suggest that PIF-dependent gene regulation coordinates multiple SAS responses, including altered stem growth via ARF18, as well as altered leaf growth and metabolism via QQS.
