Thussagunpanit Jutiporn, Jutamanee Kanapol, Homvisasevongsa Sureeporn, Suksamrarn Apichart, Yamagami Ayumi, Nakano Takeshi, Asami Tadao
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan; Department of Botany, Faculty of Science, 50 Kasetsart University, Ladyao, Chatuchak, Bangkok 10900, Thailand.
Department of Botany, Faculty of Science, 50 Kasetsart University, Ladyao, Chatuchak, Bangkok 10900, Thailand; Advanced Studies in Tropical Natural Resource, NRU-KU, 50 Kasetsart University, Ladyao, Chatuchak, Bangkok 10900, Thailand.
J Steroid Biochem Mol Biol. 2017 Sep;172:1-8. doi: 10.1016/j.jsbmb.2017.05.003. Epub 2017 May 4.
Brassinosteroids (BRs) are plant steroidal hormones that play important roles in many stages of plant growth. Several plant species produce ecdysteroids, which are known as insect molting steroid hormones. In this study, we evaluated the biological activities of three hydroxysteroidal compounds, 20-hydroxyecdysone (ECD), 7,8-dihydro-8α-20-hydroxyecdysone (DHECD), and 7,8-dihydro-5α,8α-20-hydroxyecdysone (α-DHECD), and compared their activities with that of brassinolide (BL), the most potent BR. In rice, DHECD and α-DHECD enhanced the degree of lamina inclination, as do BRs. In Arabidopsis thaliana, DHECD and α-DHECD increased hypocotyl length in the wild-type, and also partially overcame the hypocotyl shortening in the wild-type caused by 0.3μM brassinazole, a specific BR biosynthesis inhibitor. DHECD and α-DHECD partially reduced dwarfism in the BR-biosynthesis-deficient mutant det2. Treatment with DHECD or α-DHECD downregulated the expression of the BR biosynthesis genes DWF4 and CPD, which are generally, suppressed by BR, and upregulated the expression of TCH4 and SAUR-AC1, which are generally promoted by BR. However, their regulated activities were less effective than BL. Moreover, the 10M DHECD and α-DHECD induced the accumulation of dephosphorylated BIL1/BZR1 that enhanced BR signaling as a master transcription factor. In contrast, ECD did not affect rice lamina bending, Arabidopsis hypocotyl elongation, the expression levels of BR-related genes and BIL1/BZR1 phosphorylation status. Based on these results, we hypothesize that both DHECD and α-DHECD have functional activities similar to those of BR.
油菜素甾醇（BRs）是一类植物甾体激素，在植物生长的许多阶段发挥着重要作用。几种植物物种会产生蜕皮甾类化合物，这些化合物被认为是昆虫蜕皮甾体激素。在本研究中，我们评估了三种羟基甾体化合物，即20-羟基蜕皮酮（ECD）、7,8-二氢-8α-20-羟基蜕皮酮（DHECD）和7,8-二氢-5α,8α-20-羟基蜕皮酮（α-DHECD）的生物活性，并将它们的活性与最有效的BR——油菜素内酯（BL）的活性进行了比较。在水稻中，DHECD和α-DHECD与BRs一样增强了叶片倾斜度。在拟南芥中，DHECD和α-DHECD增加了野生型下胚轴的长度，并且还部分克服了由0.3μM油菜素唑（一种特异性BR生物合成抑制剂）导致的野生型下胚轴缩短。DHECD和α-DHECD部分缓解了BR生物合成缺陷型突变体det2中的矮化现象。用DHECD或α-DHECD处理会下调通常被BR抑制的BR生物合成基因DWF4和CPD的表达，并上调通常被BR促进的TCH4和SAUR-AC1的表达。然而，它们的调节活性不如BL有效。此外，10M的DHECD和α-DHECD诱导了去磷酸化的BIL1/BZR1的积累，该物质作为主要转录因子增强了BR信号传导。相比之下，ECD不影响水稻叶片弯曲、拟南芥下胚轴伸长、BR相关基因的表达水平以及BIL1/BZR1的磷酸化状态。基于这些结果，我们推测DHECD和α-DHECD都具有与BR相似的功能活性。
