Cyanobacterial blooms impose a substantial risk for submerged macrophytes in aquatic environments. This study investigated the cellular and transcriptomic responses of Vallisneria natans to microcystin-LR (MCLR) exposure, as well as abscisic acid (ABA) and strigolactone (SL), which are the major compounds in signaling networks that regulate plant defense. The results revealed that MCLR significantly (p <0.05) decreased the photosynthetic pigments and significantly (p < 0.05) increased the contents of the ABA and SL stress-related phytohormones under MCLR stress. Related genes involved in the photosynthetic pathways were down-regulated, including psbO, psbP, psbQ and psbR. In the SL biosynthetic pathway of roots under MCLR stress, related genes, such as D27 and CCD7, were down-regulated, while the CCD8 and MAX1 genes were up-regulated. In the ABA synthetic pathway, the genes LUT5, ZEP, NCED, ABA2 and AAO3 were up-regulated. Furthermore, a reduction in the content of SL enriched ABA after 3 days under MCLR stress. The potential molecular mechanism of the interactions between SL and ABA were confirmed with the relative up- and down-regulated genes in the pathway, and ABA could play a major role in plant physiology under MCLR stress. This study provides valuable information to understand the stress-related mechanisms of response of submerged macrophytes to cyanobacterial blooms.

蓝藻水华对水生环境中的沉水大型植物造成重大风险。本研究调查了苦草对微囊藻毒素-LR (MCLR) 以及脱落酸 (ABA) 和独脚金内酯 (SL) 的细胞和转录组反应，它们是调节植物防御的信号网络中的主要化合物。结果表明，MCLR胁迫下光合色素显着降低（p <0.05），ABA和SL胁迫相关植物激素含量显着增加（ p <0.05）。参与光合途径的相关基因被下调，包括psbO、psbP、psbQ和psbR. 在MCLR胁迫下根的SL生物合成途径中，相关基因如D27和CCD7下调，而CCD8和MAX1基因上调。在 ABA 合成途径中，基因LUT5、ZEP、NCED、ABA2和AAO3被上调。此外，在 MCLR 胁迫下 3 天后，SL 含量的减少使 ABA 富集。SL与ABA相互作用的潜在分子机制通过该途径中相对上调和下调的基因得到证实，ABA在MCLR胁迫下可能在植物生理中发挥重要作用。这项研究为了解沉水植物对蓝藻水华的应激反应机制提供了有价值的信息。