利用 de novo RNA Sequencings 分析甘藷在傷害下受IbHypSys 誘導之基因

Abstract

面對掠食者與病原菌的危害，植物演化出複雜的防禦機制。其中植物胜肽賀爾蒙參與在植物逆境訊息的傳導以及防禦蛋白的誘導。首個非茄科的HypSys在甘藷品系Ipomoea batatas cv. Georgia Jet中被發現，在本實驗室使用的甘藷品系Ipomoea batatas cv. Tainung 57 (台農57號，TN57)也成功釣取到IbpreproHypSys基因序列。實驗室前人證實傷害會促使成熟IbHypSys被釋放，使jasmonic acid (JA)生合成路徑被啟動，並導致H2O2的累積，進一步誘導防禦基因IPO的表現，影響木質素的生合成，使斜紋夜盜蛾的生長與發育受到抑制。本實驗利用大量表現IbpreproHypSys的甘藷轉植株建立轉錄體 (transcriptome)資料庫，篩選與IbpreproHypSys相關的候選基因，預測有19,710個contigs在傷害後的轉殖型甘藷具有更高的表現量 (fold change > 2 )，我們選擇其中9個候選基因進行後續實驗，當中IbMYB86、IbWRI1、IbSBT1.4、IbSWEET2a、IbUGT75C1會受到傷害以及短胜肽IbHypSysIV處理誘導，而IbSBT1.9、IbSBT5.3、IbPSKR2、 IbLRRAT2G33170則會在IbpreproHypSys大量表現型甘藷中被誘導。而當中多個候選基因被證實與病原菌的抗性相關，推測甘藷中的IbHypSys可能參與病原菌入侵的防禦機制。而依據候選基因在其他物種的研究，推測甘藷的IbHypSys可能具有多種訊息傳遞路徑或是調控不同反應機制的功能。

Plants have evolved defense mechanisms for survival against various kinds of predators and pathogens. It is discovered that plant peptide hormones induce defense genes and signal transmission in adversity. In Solanaceae, systemin participates in the defense mechanism of wounding. In Arabidopsis thaliana, AtPEP1 participates in the defense mechanism against pathogen. The hydroxyproline-rich glycopeptides (HypSys) are glycopeptides containing 18-20 amino acids in length, and they are processed from larger precursors. The first non-solanaceous HypSys was found in sweet potato, Ipomoea batatas cv. Georgia Jet, and it was called IbHypSys, whose precursor is IbpreproHypSys. Our groups also found IbpreproHypSys in Ipomoea batatas cv. Tainung 57. IbHypSys induced the production of jasmonic acid (JA), which caused the accumulation of H2O2 and ipomoelin (IPO) expression to protect plants from insect attacks. In this study, the transcriptome databases of sweet potato have been established. The gene expression between wild-type and transgenic sweet potato overexpressing IbpreproHypSys after 2 hr wounding was compared, and IbpreproHypSys-related transcription factors, receptors and proteases, including IbMYB86, IbWRI1, IbSBT1.4, IbSBT1.9, IbSBT5.3, IbSWEET2a, IbUGT75C1, IbPSKR2, IbLRRAT2G33170, were specially identified. Some of these candidate genes were induced upon wounding and synthetic IbHypSysIV treatment. In addition, previous studies indicated that some of these candidate genes were associated with pathogen resistance. In conclusion, IbHypSys may participates in the defense mechanism of pathogen infection.