Martínez-Vasallo Carlos, Cole Benjamin, Gallego-Bartolomé Javier, Chory Joanne, Kay Steve A, Nohales Maria A
Instituto de Biologίa Molecular y Celular de Plantas, Consejo Superior de Investigaciones Cientίficas - Universidad Politécnica de Valencia, 46022 Valencia, Spain.
Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA.
bioRxiv. 2023 Mar 23:2023.03.21.533699. doi: 10.1101/2023.03.21.533699.
For plants adapted to bright light, a decrease in the amount of light received can be detrimental to their growth and survival. Consequently, in response to shade from surrounding vegetation, they initiate a suite of molecular and morphological changes known as the shade avoidance response (SAR) through which stems and petioles elongate in search for light. Under sunlight-night cycles, the plant's responsiveness to shade varies across the day, being maximal at dusk time. While a role for the circadian clock in this regulation has long been proposed, mechanistic understanding of how it is achieved is incomplete. Here we show that the clock component GIGANTEA (GI) directly interacts with the transcriptional regulator PHYTOCHROME INTERACTING FACTOR 7 (PIF7), a key player in the response to shade. GI represses PIF7 transcriptional activity and the expression of its target genes in response to shade, thereby fine-tuning the magnitude of the response to limiting light conditions. We find that, under light/dark cycles, this function of GI is required to adequately modulate the gating of the response to shade at dusk. Importantly, we also show that GI expression in epidermal cells is sufficient for proper SAR regulation.
对于适应强光的植物而言，接收到的光照量减少可能对其生长和存活不利。因此，为应对周围植被的遮荫，它们会启动一系列分子和形态变化，即所谓的避荫反应（SAR），通过该反应，茎和叶柄会伸长以寻找光照。在阳光 - 夜晚循环下，植物对遮荫的反应在一天中有所不同，在黄昏时最大。虽然长期以来人们一直认为生物钟在这种调节中起作用，但对其实现机制的理解并不完整。在这里，我们表明生物钟组件巨蛋白（GI）直接与转录调节因子光敏色素相互作用因子7（PIF7）相互作用，PIF7是遮荫反应中的关键参与者。GI抑制PIF7的转录活性及其在遮荫反应中的靶基因表达，从而微调对有限光照条件的反应程度。我们发现，在光/暗循环下，GI的这一功能对于在黄昏时充分调节对遮荫反应的门控是必需的。重要的是，我们还表明表皮细胞中的GI表达足以实现对SAR的适当调节。
