Mechanisms for Desiccation Tolerance in Cyanobacterium Nostoc commune

Potts 9513157活跃生长的细胞对空气干燥特别敏感，大多数细胞在暴露于大气中时立即死亡。 相比之下，原核生物和真核生物的一个小的，不同的群体的成员有能力承受最严重的细胞水分不足。 它们如何做到这一点仍然是生物学中一个有趣的问题。 一种蓝细菌，普通念珠藻，具有显著的耐干燥能力，并已被开发为脱水原核细胞的模型。 对N.地木耳合成水分胁迫多肽（Wsp），其占总可溶性细胞蛋白的约70%和干燥菌落干重的约2%。 Wsp在风干状态下储存数十年的细胞中保持稳定。 Wsp分泌并积累在一个复杂的胞外多糖（EPS）中，完全包裹细胞丝。 本研究的主要目的是：1）从念珠藻中分离wsp基因，并对其侧翼区和调控元件进行鉴定; 2）了解wsp基因的转录和合成是如何受水分胁迫调控的; 3）Wsp基因的结晶。 N. commune代表细胞在长期干燥期间用于实现保护的两种策略。 波茨博士发现的证据表明，Wsp在这两种策略中的一种或两种中都发挥了作用。 关于N.公社克服急性细胞水分亏缺将提供一个深入了解所有生物体的脱水耐受性的潜在机制。

Potts9513157Actively growing cells are particularly sensitive to air-drying and most die instantly upon exposure to the atmosphere. In contrast, the members of a small, diverse group of prokaryotic and eukaryotic organisms have the capacity to withstand the most acute of cell-water deficits. How they do so remains an intriguing problem in biology. One cyanobacterium, Nostoc Commune, has a marked capacity for desiccation tolerance and has been developed as a model for the anhydrobiotic prokaryotic cell. In response to air-drying cells of N. commune synthesize water stress polypeptides (Wsp) that constitute around 70% of the total soluble cell protein and approximately 2% of the dry weight of a desiccated colony. Wsp remain stable in cells stored for decades in the air-dried state. Wsp are secreted and accumulate within a complex extracellular polysaccharide (EPS) that completely envelops the cell filaments. Within the EPS the Wsp form multimeric complexes, through strong ionic interactions, with a secreted, water-soluble UV-A/B-absorbing pigment (UVP).The principle objectives of this study are: 1) to isolate wsp from Nostoc, and to characterize the gene, its flanking regions and its control elements; 2) to understand how wsp transcription and Wsp synthesis are regulated by water stress; and 3) to crystallize Wsp. The secretion of EPS and UVP by N. commune represent two strategies that the cells use to achieve protection during long-term desiccation. The evidence found by Dr. Potts suggests that Wsp play a role in one or both of these strategies. The knowledge of how N. commune overcomes acute cell-water deficit will provide an insight into the underlying mechanisms of desiccation tolerance in all organisms.