Effect of nutrient limitation of cyanobacteria on protease inhibitor production and fitness of Daphnia magna
Effect of nutrient limitation of cyanobacteria on protease inhibitor production and fitness of Daphnia magna
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蓝藻营养限制对大型溞蛋白酶抑制剂产生和适应性的影响
DOI：
10.1242/jeb.088849
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发表时间：
2013
影响因子：
2.8
通讯作者：
E. von Elert
中科院分区：
文献类型：
--
作者：
A. Schwarzenberger;Thomas Sadler;E. von Elert
摘要在陆地和水生生态系统中，食草动物-植物相互作用已经得到了很好的研究，因为它们对能量和物质的营养转移至关重要。在营养丰富的淡水生态系统中，初级生产者和食草动物之间的相互作用在很大程度上由水蚤和蓝藻代表。蓝藻水华在湖泊和池塘中的发生，至少部分归因于蓝藻毒素，这对浮游蓝藻的主要食草动物，即水蚤产生了负面影响。在这些蓝藻毒素中，广泛存在的蛋白酶抑制剂。这些抑制剂已被证明（体外和原位）抑制水蚤肠道中最重要的消化蛋白酶，即胰蛋白酶和胰凝乳蛋白酶，并减少水蚤生长。在这项研究中，我们生长的蓝藻微囊藻菌株BM 25的营养丰富，N-耗尽或P-耗尽的培养基。我们鉴定了三种不同的微肽是BM 25对胰凝乳蛋白酶的抑制活性的原因。微肽含量取决于营养物质的可用性：而N限制导致每生物量的微肽浓度较低，P限制导致这些糜蛋白酶抑制剂的产量较高。BM 25微肽含量的改变伴随着对大型蚤适合度的影响的改变：微肽含量越高，对大型蚤的IC 50值越低。大肠蛋白酶，反之亦然。与预期的结果一致，低N-耗竭BM 25中的微肽素含量导致了较高的体细胞生长。麦格纳因此，蛋白酶抑制剂可以被视为一种营养依赖的防御食草动物。有趣的是，虽然蓝藻的磷限制导致了较高的微肽素含量，但D。当它们被喂食去磷的BM 25时，观察到magna。这可能是由于减少消化率的P-耗尽细胞与puerosan厚粘液鞘。这些结果表明，无论是食草动物和蓝藻受益于磷减少消化率和生长抑制，这是一个有趣的起点，为进一步的研究。
SUMMARY Herbivore–plant interactions have been well studied in both terrestrial and aquatic ecosystems as they are crucial for the trophic transfer of energy and matter. In nutrient-rich freshwater ecosystems, the interaction between primary producers and herbivores is to a large extent represented by Daphnia and cyanobacteria. The occurrence of cyanobacterial blooms in lakes and ponds has, at least partly, been attributed to cyanotoxins, which negatively affect the major grazer of planktonic cyanobacteria, i.e. Daphnia. Among these cyanotoxins are the widespread protease inhibitors. These inhibitors have been shown (both in vitro and in situ) to inhibit the most important group of digestive proteases in the gut of Daphnia, i.e. trypsins and chymotrypsins, and to reduce Daphnia growth. In this study we grew cultures of the cyanobacterium Microcystis sp. strain BM25 on nutrient-replete, N-depleted or P-depleted medium. We identified three different micropeptins to be the cause for the inhibitory activity of BM25 against chymotrypsins. The micropeptin content depended on nutrient availability: whereas N limitation led to a lower concentration of micropeptins per biomass, P limitation resulted in a higher production of these chymotrypsin inhibitors. The altered micropeptin content of BM25 was accompanied by changed effects on the fitness of Daphnia magna: a higher content of micropeptins led to lower IC50 values for D. magna gut proteases and vice versa. Following expectations, the lower micropeptin content in the N-depleted BM25 caused higher somatic growth of D. magna. Therefore, protease inhibitors can be regarded as a nutrient-dependent defence against grazers. Interestingly, although the P limitation of the cyanobacterium led to a higher micropeptin content, high growth of D. magna was observed when they were fed with P-depleted BM25. This might be due to reduced digestibility of P-depleted cells with putatively thick mucilaginous sheaths. These findings indicate that both the grazer and the cyanobacterium benefit from P reduction in terms of digestibility and growth inhibition, which is an interesting starting point for further studies.