Development of artificial seeds for long-term preservation of tropical medicinal plants and microalgae

热带植物和微藻是寻找适用于医药和农用化学品的新型生物活性化合物的诱人资源。然而，由于温室效应和酸雨等环境恶化，它们中的许多物种处于灭绝的边缘。这项研究的目的是开发人工种子，以长期保存那些有价值的东西。超低温保存(液氮保存)是一种有效的长期保存各种生物种质的方法。因此，本研究采用包埋-脱水法对植物和微藻进行超低温保存，将材料包裹在海藻酸钙珠中形成人工种子，然后在液氮中进行风干脱水，成功地将3种能够产生生物活性物质的植物毛状根进行了超低温保存。此外，该技术还适用于多种真核微藻和蓝藻的超低温保存，在毛状根和真核淡水微藻(绿藻)中加入脱落酸(ABA)后，脱水后的存活率显著提高，表明ABA提高了这些材料的脱水耐性。结果表明，采用包埋-脱水技术超低温保存药用植物毛状根和微藻细胞的人工种子具有较好的长期保存效果。将开发的技术应用于不同种类的热带植物和微型植物正在进行中。

Tropical plants and microalgae are attractive resources for search of novel bioactive compounds applicable to medicines and agrichemicals. However, many species of them are on the point of extermination because of environmental deterioration such as greenhouse effect and acid rain. The aim of this research is to develop artificial seeds for long-term preservation of those valuable. Cryopreservation (preservation in liquid nitrogen) is well known as a useful method for long-term preservation of germplasm of various organisms. Therefore, an encapsulation-dehydration was employed in this study for cryopreservation of plants and microalgae, in which materials were encapsulated in Ca-alginate beads to form artificial seeds and dehydrated by air-drying before cooling in liquid nitrogen.By using this technique, hairy roots of three plant species capable of producing bioactive compounds were successfully cryopreserved. Moreover, this technique was applicable to cryopreservation of several strains of eucaryotic microalga and cyanobacterium.In case of hairy roots and eucaryotic freshwater microalgae (green algae), survival rates after dehydration were markedly increased by addition of abscisic acid (ABA) into preculture media and beads, indicating that ABA increased desiccation tolerance of these materials. Consequently, their survival rates after cooling liquid nitrogen increased to more than 70%, which is acceptable as a sufficient rate for stable long-term preservation.These results indicate that cryopreservation using encapsulation-dehydration technique is useful for long-term preservation of artificial seeds encapsulating hairy roots of medicinal plants and microalgal cells. Application of the technique developed to different species of tropical plants and microalge is in progress.