Habibur Rahman Pramanik M, Imai Ryozo
Winter Stress Laboratory, National Agricultural Research Center for Hokkaido Region, National Agricultural and Bio-oriented Research Organization, Hitsujigaoka 1, 062-8555, Toyohira-ku, Sapporo, Japan.
Department of Crop Botany, Bangladesh Agricultural University, Mymensing, Bangladesh.
Plant Mol Biol. 2005 Aug;58(6):751-762. doi: 10.1007/s11103-005-7404-4.
Trehalose serves as a stress protectant and/or reserve carbohydrate in a variety of organisms including bacteria, yeast, and invertebrates. Recently, trace amounts of trehalose have been detected in higher plants, although the function of trehalose in plants remains unknown. A cDNA clone (OsTPP1) encoding a putative trehalose-6-phosphate phosphatase (TPP) for trehalose biosynthesis was isolated from rice. Functionality of the clone was demonstrated by complementation of a yeast mutant and enzymatic activity of the recombinant protein. Northern blots revealed that the OsTPP1 transcript levels were fairly low or under detectable limits in most of the tissues under ambient conditions but were highly induced within 1-2 h of chilling stress (12 degrees C) in both root and shoot tissues of seedlings. This induction was transient and disappeared after 6 h of the chilling stress. Transient expression of OsTPP1 was also induced under severe chilling stress (4 degrees C) as well as salinity and drought stresses at ambient temperatures. Application of exogenous ABA (50 microM) resulted in a transient increase of OsTPP1 expression within 20 min of the treatment, thereby suggesting involvement of ABA in OsTPP1 gene regulation. Measurements of total cellular TPP activity and trehalose content in roots indicated that both TPP activity and trehalose levels were transiently increased after chilling (12 degrees C) stress. Collectively, the data indicate that transient activation of trehalose biosynthesis is involved in early chilling stress response in rice. Possible functions of trehalose in the early stages of chilling stress response are discussed.
海藻糖在包括细菌、酵母和无脊椎动物在内的多种生物体中作为应激保护剂和/或储备碳水化合物。最近，在高等植物中检测到痕量的海藻糖，尽管海藻糖在植物中的功能仍然未知。从水稻中分离出一个编码假定的海藻糖-6-磷酸磷酸酶（TPP）用于海藻糖生物合成的cDNA克隆（OsTPP1）。通过酵母突变体的互补和重组蛋白的酶活性证明了该克隆的功能。Northern杂交显示，在环境条件下，大多数组织中OsTPP1转录本水平相当低或低于可检测限度，但在幼苗的根和地上部组织中，低温胁迫（12℃）1-2小时内OsTPP1转录本水平被高度诱导。这种诱导是短暂的，在低温胁迫6小时后消失。在严重低温胁迫（4℃）以及环境温度下的盐胁迫和干旱胁迫下，OsTPP1的瞬时表达也被诱导。施加外源脱落酸（50μM）导致处理后20分钟内OsTPP1表达瞬时增加，从而表明脱落酸参与OsTPP1基因调控。对根中总细胞TPP活性和海藻糖含量的测量表明，低温（12℃）胁迫后TPP活性和海藻糖水平均瞬时增加。总体而言，数据表明海藻糖生物合成的瞬时激活参与水稻早期低温胁迫反应。讨论了海藻糖在低温胁迫反应早期阶段的可能功能。
