Hellwege E M, Dietz K J, Hartung W
Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Germany.
Planta. 1996;198(3):423-32. doi: 10.1007/BF00620059.
The conversion of the submerged form of Riccia fluitans to the landform either by transfer to a moist solid surface or by treatment with abscisic acid (ABA), is accompanied by the formation of a set of new polypeptides and concomitant down-regulation of other polypeptides. Changes in gene expression were analyzed by two-dimensional separations of proteins and differential screening of a cDNA library. One of the landform-specific proteins might depend on the expression of the newly discovered Ric 1 gene. The deduced amino acid sequence of the isolated Ric 1 cDNA clone codes for a protein with a molecular mass of 30.1 kDa. This polypeptide possesses two amino acid sequences which are repeated five times each and it is largely hydrophilic with the exception of a hydrophobic carboxyl-terminal region. Under ABA treatment the expression of the Ric 1 mRNA had already reached its maximum after 1 h of incubation. Transferring submerged thalli onto an agar surface resulted in a slower induction. The Ric 1 gene product shows homology to an embryo-specific polypeptide of carrot seeds and to the group 3 of late-embryogenesis-abundant (LEA) proteins. Interestingly, ABA treatment improved the desiccation tolerance of the submerged thalli. Additionally, ABA stimulated the synthesis of a protein which is immunologically related to a tonoplast protein. This finding, together with the fact that the ABA-induced landform exhibits an increased activity of several vacuolar enzymes, may indicate a special role of the tonoplast and the vacuole during ABA-induced conversion of the thallus from the submerged to the terrestrial form.
通过转移至潮湿固体表面或用脱落酸（ABA）处理，将漂浮藓的 submerged 形式转化为陆地形式时，会伴随着一组新多肽的形成以及其他多肽的下调。通过蛋白质二维分离和 cDNA 文库差异筛选分析基因表达变化。一种陆地形式特异性蛋白可能依赖于新发现的 Ric 1 基因的表达。分离出的 Ric 1 cDNA 克隆推导的氨基酸序列编码一种分子量为 30.1 kDa 的蛋白质。该多肽具有两个分别重复五次的氨基酸序列，除了疏水的羧基末端区域外，它主要是亲水的。在 ABA 处理下，Ric 1 mRNA 的表达在孵育 1 小时后已达到最大值。将 submerged 叶状体转移到琼脂表面诱导速度较慢。Ric 1 基因产物与胡萝卜种子的胚胎特异性多肽以及晚期胚胎发育丰富（LEA）蛋白的第 3 组具有同源性。有趣的是，ABA 处理提高了 submerged 叶状体的耐旱性。此外，ABA 刺激了一种与液泡膜蛋白免疫相关的蛋白质的合成。这一发现，连同 ABA 诱导的陆地形式表现出几种液泡酶活性增加这一事实，可能表明液泡膜和液泡在 ABA 诱导叶状体从 submerged 形式向陆地形式转化过程中具有特殊作用。
