Schmidt Frederik Bøgeskov, Cho Seok Keun, Olsen Carl Erik, Yang Seong Wook, Møller Birger Lindberg, Jørgensen Kirsten
Plant Biochemistry Laboratory Department of Plant and Environmental Sciences University of Copenhagen Copenhagen Denmark.
VILLUM Research Center "Plant Plasticity" Copenhagen Denmark.
Plant Direct. 2018 Feb 26;2(2):e00038. doi: 10.1002/pld3.38. eCollection 2018 Feb.
Cyanogenic glucosides are present in many plants, including eudicots, monocots, and ferns and function as defence compounds based on their ability to release hydrogen cyanide. In this study, the diurnal rhythm of cyanogenic glucoside content and of transcripts and enzymes involved in their biosynthesis was monitored in cassava plants grown in a glasshouse under natural light conditions. Transcripts of 1, , / and were at minimal levels around 9 p.m., increased during the night and decreased following onset of early morning light. Transcripts of and showed more subtle variations with a maximum reached in the afternoon. Western blots showed that the protein levels of CYP71E7/11 and UGT85K4/5 decreased during the light period to a near absence around 4 p.m. and then recovered during the dark period. Transcript and protein levels of linamarase were stable throughout the 24-hr cycle. The linamarin content increased during the dark period. In the light period, spikes in the incoming solar radiation were found to result in concomitantly reduced linamarin levels. In silico studies of the promoter regions of the biosynthetic genes revealed a high frequency of light, abiotic stress, and development-related transcription factor binding motifs. The synthesis and endogenous turnover of linamarin are controlled both at the transcript and protein levels. The observed endogenous turnover of linamarin in the light period may offer a source of reduced nitrogen to balance photosynthetic carbon fixation. The rapid decrease in linamarin content following light spikes suggests an additional function of linamarin as a ROS scavenger.
含氰糖苷存在于许多植物中，包括双子叶植物、单子叶植物和蕨类植物，基于其释放氰化氢的能力，它们作为防御化合物发挥作用。在本研究中，监测了在自然光条件下温室种植的木薯植株中含氰糖苷含量以及参与其生物合成的转录本和酶的昼夜节律。1, , / 和 的转录本在晚上9点左右处于最低水平，在夜间增加，并在清晨光照开始后下降。 和 的转录本变化较为细微，在下午达到最大值。蛋白质免疫印迹显示，CYP71E7/11和UGT85K4/5的蛋白质水平在光照期间下降，在下午4点左右几乎消失，然后在黑暗期间恢复。亚麻苦苷酶的转录本和蛋白质水平在整个24小时周期内保持稳定。亚麻苦苷含量在黑暗期间增加。在光照期间，发现入射太阳辐射的峰值会导致亚麻苦苷水平相应降低。对生物合成基因启动子区域的计算机模拟研究揭示了光、非生物胁迫和发育相关转录因子结合基序的高频率。亚麻苦苷的合成和内源性周转在转录本和蛋白质水平上均受到控制。在光照期间观察到的亚麻苦苷内源性周转可能提供了一种还原氮源，以平衡光合碳固定。光照峰值后亚麻苦苷含量的快速下降表明亚麻苦苷作为活性氧清除剂的额外功能。
