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

热带植物和微藻是寻找新型药物和农药活性化合物的重要资源。然而，由于环境恶化，如温室效应和酸雨，许多物种濒临灭绝。本研究的目的是开发人工种子，长期保存那些有价值的。低温保存（在液氮中保存）是众所周知的用于长期保存各种生物种质的有用方法。因此，本研究采用海藻酸钙微球包埋人工种子，并在液氮中冷却前风干脱水的方法，对3种能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（绿色藻）的预培养液和微珠中添加脱落酸（阿坝），可显著提高其脱水后的存活率，表明阿坝提高了这些材料的脱水耐受性。结果表明，液氮冷冻后的存活率可达70%以上，可以满足长期稳定保存的要求，说明冷冻脱水技术可用于药用植物毛状根和微藻细胞人工种子的长期保存。目前正在将所开发的技术应用于不同种类的热带植物和微藻。

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.