Basical Experimental Teaching Center, Gansu Agricultural University, Lanzhou, 730070, Gansu Province, China.
College of Horticulture, Gansu Agricultural University, Lanzhou, 730070, Gansu Province, China.
BMC Plant Biol. 2022 Aug 17;22(1):403. doi: 10.1186/s12870-022-03747-x.
Glucoraphanin (GRA) is present in the seeds and nutrient organs of broccoli and is the precursor of the anti-cancer compound sulforaphane (SF). The hairy roots obtained by infecting broccoli (Brassica oleracea L. var. Italic Planch) leaves with Agrobacterium rhizogenes (ATCC15834) are phytohormonally autonomous, genetically stable, and can produce large amounts of the anti-cancer substance SF. Melatonin (MT) is a natural hormone widely found in plants. Studies have shown that melatonin can regulate the synthesis of secondary metabolites of downstream targets by mediating the synthesis of signal molecules. However, whether MT regulates the synthesis of NO and HO and mediates the synthesis mechanism of secondary metabolites, GRA and SF, is not yet clear. In this study, the hairy roots of broccoli were treated with 500 μmol/L MT, and the genome of broccoli (Brassica oleracea L. var. botrytis L) was used as the reference genome for transcriptome analysis. By this approach, we found that MT regulates the synthesis of NO and HO and mediates the synthesis of secondary metabolites GRA and SF. GO annotations indicated that DEGs involved in the MT treatment of broccoli hairy roots were mainly related to catalytic activity, cells, and metabolic processes; the KEGG pathway analysis indicated that MT treatment likely affects the hormone signal transduction process in broccoli hairy roots; broccoli hairy roots were treated with 500 μmol/L MT for 0, 6, 12, 20, and 32 h, respectively; compared with 0 h, the yield of GRA and SF increased under the other treatments. The highest yields of GRA and SF occurred at 12 h. The NO content was the highest at 12 h, and the HO content was positively correlated with MT concentration. The content of NO and HO were regulated, and the content of GRA and SF was increased under MT treatment. NO synthase inhibitor (L-NAME and TUN) could effectively inhibit the content of NO in broccoli hairy roots and reduce GRA and SF yield; MT could regulate NO levels by regulating NO synthesis-related enzymes and could alleviate the reduction of NO content in tissue cells caused by NO synthase inhibitor and promote NO synthesis. These results have important theoretical implications for understanding the regulation of GRA and SF synthesis events by NO and HO.
萝卜硫素（GRA）存在于西兰花的种子和营养器官中，是抗癌化合物萝卜硫素（SF）的前体。发根农杆菌（Agrobacterium rhizogenes）感染西兰花（Brassica oleracea L. var. Italic Planch）叶片获得的毛状根具有植物激素自主性、遗传稳定性，并且可以大量产生抗癌物质 SF。褪黑素（MT）是一种广泛存在于植物中的天然激素。研究表明，褪黑素可以通过调节信号分子的合成来调节下游靶标次生代谢物的合成。然而，MT 是否调节 NO 和 HO 的合成以及介导次生代谢物 GRA 和 SF 的合成机制尚不清楚。在本研究中，用 500μmol/L MT 处理西兰花毛状根，以西兰花（Brassica oleracea L. var. botrytis L）基因组作为转录组分析的参考基因组。通过这种方法，我们发现 MT 调节 NO 和 HO 的合成，并介导次生代谢物 GRA 和 SF 的合成。GO 注释表明，参与 MT 处理的西兰花毛状根的 DEGs 主要与催化活性、细胞和代谢过程有关；KEGG 通路分析表明，MT 处理可能影响西兰花毛状根中的激素信号转导过程；用 500μmol/L MT 分别处理西兰花毛状根 0、6、12、20 和 32 h；与 0 h 相比，其他处理下 GRA 和 SF 的产量增加。GRA 和 SF 的产量在 12 h 时最高。NO 含量在 12 h 时最高，HO 含量与 MT 浓度呈正相关。在 MT 处理下，NO 和 HO 的含量受到调节，GRA 和 SF 的含量增加。NO 合酶抑制剂（L-NAME 和 TUN）可以有效抑制西兰花毛状根中 NO 的含量，降低 GRA 和 SF 的产量；MT 可以通过调节与 NO 合成相关的酶来调节 NO 水平，并可以减轻 NO 合酶抑制剂引起的组织细胞中 NO 含量的降低，促进 NO 的合成。这些结果对于理解 NO 和 HO 对 GRA 和 SF 合成事件的调节具有重要的理论意义。
