State Key Laboratory of Southwestern Chinese Medicine Resources, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, Sichuan, China; College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, Sichuan, China.
State Key Laboratory of Southwestern Chinese Medicine Resources, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, Sichuan, China; College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, Sichuan, China.
Int J Biol Macromol. 2024 Nov;279(Pt 2):135234. doi: 10.1016/j.ijbiomac.2024.135234. Epub 2024 Aug 30.
The mechanisms by which low light accelerates starch macromolecules degradation by auxin and gibberellin (GA) in geophytes during sprouting remain largely unknown. This study investigated these mechanisms in saffron, grown under low light (50 μmol m s) and optimal light (200 μmol m s) during the sprouting phase. Low light reduced starch concentration in corms by 34.0 % and increased significantly sucrose levels in corms, leaves, and leaf sheaths by 19.2 %, 9.8 %, and 134.5 %, respectively. This was associated with a 33.3 % increase in GA level and enhanced auxin signaling. Leaves synthesized IAA under low light, which was transported to the corms to promote GA synthesis, facilitating starch degradation through a 228.7 % increase in amylase activity. Exogenous applications of GA and IAA, as well as the use of their synthesis or transport inhibitors, confirmed the synergistic role of these phytohormones in starch metabolism. The unigenes associated with GA biosynthesis and auxin signaling were upregulated under low light, highlighting the IAA-GA module role in starch degradation. Moreover, increased respiration rate and invertase activity, crucial for ATP biosynthesis and the tricarboxylic acid cycle, were consistent with the upregulation of related unigenes, suggesting that auxin signaling accelerates starch degradation by promoting energy metabolism. Upregulated of auxin signaling (CsSAUR32) and starch metabolism (CsSnRK1) genes under low light suggests that auxin directly regulate starch degradation in saffron corms. This study elucidates that low light modulates auxin and GA interactions to accelerate starch degradation in saffron corms during sprouting, offering insights for optimizing agricultural practices under suboptimal light conditions.
在发芽过程中，低光如何通过生长素和赤霉素 (GA) 加速块茎中淀粉大分子的降解，其机制在很大程度上尚不清楚。本研究在番红花的发芽阶段，分别在低光 (50 μmol m s) 和最佳光照 (200 μmol m s) 下生长，研究了这些机制。低光使球茎中的淀粉浓度降低了 34.0%，并显著增加了球茎、叶片和叶鞘中的蔗糖水平，分别增加了 19.2%、9.8%和 134.5%。这与 GA 水平增加 33.3%和生长素信号增强有关。叶片在低光下合成 IAA，然后运输到球茎中促进 GA 合成，通过淀粉酶活性增加 228.7%来促进淀粉降解。GA 和 IAA 的外源应用以及它们合成或运输抑制剂的使用，证实了这些植物激素在淀粉代谢中的协同作用。与 GA 生物合成和生长素信号相关的基因在低光下上调，突出了 IAA-GA 模块在淀粉降解中的作用。此外，呼吸速率和转化酶活性的增加，这对于 ATP 合成和三羧酸循环至关重要，与相关基因的上调一致，表明生长素信号通过促进能量代谢加速淀粉降解。低光下生长素信号 (CsSAUR32) 和淀粉代谢 (CsSnRK1) 基因的上调表明，生长素直接调节番红花球茎中的淀粉降解。本研究阐明了低光调节生长素和 GA 的相互作用，以加速番红花球茎在发芽过程中的淀粉降解，为优化低光照条件下的农业实践提供了见解。
