Hollenbach B, Schreiber L, Hartung W, Dietz K J
Julius-von-Sachs Institut für Biowissenschaften, W{urzburg, Germany.
Planta. 1997 Sep;203(1):9-19. doi: 10.1007/s00050159.
In order to investigate the nature of genes expressed in leaf epidermal cells of higher plants, we have identified the nucleotide sequence of a cDNA designated ltp 7a2b encoding a novel nonspecific lipid transfer protein of barley (Hordeum vulgare L. cv. Gerbel). The cDNA of 755 basepairs contains an open reading frame of 366 nucleotides coding for a 12.3-kDa polypeptide. The first 29 amino acids constitute the putative signal peptide, characteristic for targeting to the secretory pathway. Analysis of mRNA levels by Northern blotting indicated that ltp 7a2b is preferentially expressed in the leaf epidermis. Levels of mRNA decreased during ageing of leaf tissue. Expression of ltp 7a2b was stimulated by a factor of 2 - 3 when the seedlings were grown in the presence of cadmium (10 - 1600 microM). Concomitantly, the primary leaves of Cd-exposed seedlings contained elevated levels of abscisic acid and thicker was layer of the cuticle. At 100 microM Cd in the hydroponic medium, the was cover was increased by 50%. The increase in abscisic acid content, ltp 7a2b mRNA and was coverage was either not seen, or seen much less, in Ni- and Zn-stressed seedlings. The data add circumstantial evidence to the recently proposed hypothesis that nonspecific lipid transfer proteins function in transfer of cutin and/or wax monomers from the site of synthesis in the cell to the cuticle.
为了研究高等植物叶片表皮细胞中表达基因的性质，我们鉴定了一个名为ltp 7a2b的cDNA的核苷酸序列，该序列编码大麦（Hordeum vulgare L. cv. Gerbel）一种新的非特异性脂质转移蛋白。这个755个碱基对的cDNA包含一个366个核苷酸的开放阅读框，编码一个12.3 kDa的多肽。前29个氨基酸构成推测的信号肽，这是靶向分泌途径的特征。通过Northern印迹分析mRNA水平表明，ltp 7a2b在叶片表皮中优先表达。在叶片组织衰老过程中，mRNA水平下降。当幼苗在镉（10 - 1600 microM）存在下生长时，ltp 7a2b的表达受到2 - 3倍的刺激。同时，暴露于镉的幼苗的初生叶中脱落酸水平升高，角质层更厚。在水培培养基中镉浓度为100 microM时，角质层覆盖增加了50%。在镍和锌胁迫的幼苗中，脱落酸含量、ltp 7a2b mRNA和角质层覆盖的增加要么没有观察到，要么观察到的程度要小得多。这些数据为最近提出的假说提供了间接证据，即非特异性脂质转移蛋白在将角质和/或蜡单体从细胞内的合成部位转移到角质层中发挥作用。
