Iwamoto Koji, Shiraiwa Yoshihiro
Functional Biosciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
Mar Biotechnol (NY). 2005 Sep-Oct;7(5):407-15. doi: 10.1007/s10126-005-0029-4. Epub 2005 Aug 4.
Mannitol, one of the most widely occurring sugar alcohol compounds, is found in bacteria, fungi, algae, and plants. In these organisms the compound acts as a compatible solute and has multiple functions, including osmoregulation, storage, and regeneration of reducing power, and scavenging of active oxygen species. Because of the diverse functions of mannitol, introducing the ability to accumulate it has been a hallmark of attempts to generate highly salt-tolerant transgenic plants. However, transgenic plants have not yet improved significantly in their salt tolerance. Recently, we purified and characterized 2 enzymes that biosynthesize mannitol, mannitol-1-phosphate dehydrogenase (M1PDH) and mannitol-1-phosphate-specific phosphatase, from the marine red alga Caloglossa continua, which grows in estuarine areas where tide levels fluctuate frequently. The activation of Caloglossa M1PDH is unique in that it is regulated by salt concentration at enzyme level. In this review we focus on the metabolism of mannitol, mainly in marine photosynthetic organisms, and suggest how this might be applied to producing salt-tolerant transgenic plants.
甘露醇是最广泛存在的糖醇化合物之一，存在于细菌、真菌、藻类和植物中。在这些生物体中，该化合物作为一种相容性溶质，具有多种功能，包括渗透调节、储存、还原力的再生以及活性氧的清除。由于甘露醇具有多种功能，引入积累甘露醇的能力一直是培育高度耐盐转基因植物尝试的一个标志。然而，转基因植物的耐盐性尚未得到显著改善。最近，我们从生长在潮汐水平频繁波动的河口区域的海洋红藻连续舌藻中纯化并鉴定了两种生物合成甘露醇的酶，即甘露醇-1-磷酸脱氢酶（M1PDH）和甘露醇-1-磷酸特异性磷酸酶。连续舌藻M1PDH的激活具有独特性，因为它在酶水平上受盐浓度调节。在这篇综述中，我们主要关注海洋光合生物中甘露醇的代谢，并提出如何将其应用于培育耐盐转基因植物。
