Imanishi S, Kito-Nakamura K, Matsuoka K, Morikami A, Nakamura K
Laboratory of Biochemistry, School of Agricultural Sciences, Nagoya University, Japan.
Plant Cell Physiol. 1997 Jun;38(6):643-52. doi: 10.1093/oxfordjournals.pcp.a029216.
Treatment of sweet potato plants cultured in vitro with a vapor of methyl jasmonate (MeJA) induced an accumulation in leaves of a large amount of protein with an apparent molecular mass of 18 kDa. This protein, designated ipomoelin, was purified, and the amino acid sequences of proteolytic fragments were determined. Screening a cDNA library of MeJA-treated leaves by oligonucleotide probes designed from the peptide sequences identified a clone that could code for a polypeptide with 154 amino acids. The deduced amino acid sequence of ipomoelin showed an overall amino acid identity of 25% with the salt-inducible SalT protein of rice. In addition, the C-terminal 70 amino acid sequence of ipomoelin showed about 50% identity with the C-terminal amino acid sequences of seed lectins from Moraceae. The gene for ipomoelin was present in a few copies in the genome of sweet potato. The mRNA for ipomoelin was detected in leaves and petioles, but not in stems and tuberous roots, of sweet potato plants grown in the field. Mechanical wounding of leaves induced ipomoelin mRNA both locally and systemically, while treatment of leaves with ABA, salt, or a high level of sucrose did not induce ipomoelin mRNA. By contrast, ABA-inducible mRNA for sporamin was not induced by MeJA. These results suggest that ipomoelin is involved in defensive reactions of leaves in response to wounding and that JA-mediated wound-induction of ipomoelin occurs independently of ABA.
用茉莉酸甲酯（MeJA）蒸汽处理体外培养的甘薯植株，可诱导叶片中积累大量表观分子量为18 kDa的蛋白质。这种蛋白质被命名为甘薯素，经过纯化后，测定了其蛋白水解片段的氨基酸序列。根据肽序列设计寡核苷酸探针，筛选MeJA处理叶片的cDNA文库，鉴定出一个可编码含154个氨基酸多肽的克隆。甘薯素推导的氨基酸序列与水稻盐诱导型SalT蛋白的总体氨基酸同一性为25%。此外，甘薯素的C端70个氨基酸序列与桑科种子凝集素的C端氨基酸序列显示出约50%的同一性。甘薯素基因在甘薯基因组中以几个拷贝存在。在田间生长的甘薯植株的叶片和叶柄中检测到甘薯素的mRNA，但在茎和块根中未检测到。叶片的机械损伤在局部和系统水平上均诱导甘薯素mRNA的产生，而用脱落酸（ABA）、盐或高浓度蔗糖处理叶片则不会诱导甘薯素mRNA的产生。相比之下，MeJA不会诱导ABA诱导的sporamin mRNA的产生。这些结果表明，甘薯素参与叶片对损伤的防御反应，并且JA介导的甘薯素伤口诱导独立于ABA发生。
