Abstract The microbial communities associated with plant's compartments and the expression of the chloroplast chaperonin Hsp60 have been simultaneously analyzed during the diel cycle in the marine seagrass Thalassia hemprichii from the lagoon of Magoodhoo island (Maldives), characterized by remarkable daily shifts in temperature and light. Plants showed a significant up-regulation of Hsp60 expression from 8.00 a.m. to 2.00 p.m., in correspondence with the increase in temperature and light, confirming their role as defense mechanism against photoinhibition and oxidative damage. However, a further significant increase of the Hsp60 level was also observed when irradiance and temperature dropped, suggesting that the cellular stress was still in progress. The plant-associated microbial communities showed differences by plant compartment and sampling time, with the aboveground compartment (leaves) being much more dynamic than the belowground one (roots/rhizomes). In the phyllosphere, a progressive shift during the day from the absolute dominance of the Gammaproteobacteria class, mainly constituted of Enterobacteraceae family, to the increase of the biodiversity due to the rise of Alphaproteobacteria was observed. Belowground, the microbial diversity was much lower than aboveground, being Gammaproteobacteria the most represented class throughout all sampling times. Vibrionaceae family was the most abundant at 8:00 a.m. and 6.00 p.m. decreasing slightly at 2.00 p.m., partially replaced by Halomonadaceae. The combined biochemical and microbial markers allows to assess the plant stress response and to deepen the knowledge on the seagrasses adaptation to harsh and changing environmental conditions, resulting useful to detect early signs of change in an organism's physiological state. Furthermore, the variation of Hsp60 expression and associated bacterial communities in response to light and temperature fluctuations support the ‘holobiont’ theory, which considers the plant/microorganisms association as a functional unit, as suggested for corals.

中文翻译：

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马尔代夫海草 Thalassia hemprichii 相关微生物群落的日变化和 Hsp60 表达

摘要 在来自 Magoodhoo 岛（马尔代夫）泻湖的海洋海草 Thalassia hemprichii 的昼夜循环期间，同时分析了与植物区室相关的微生物群落和叶绿体伴侣蛋白 Hsp60 的表达，其特征是温度和光线的显着每日变化。从上午 8 点到下午 2 点，植物表现出 Hsp60 表达的显着上调，这与温度和光照的增加相对应，证实了它们作为抵御光抑制和氧化损伤的防御机制的作用。然而，当辐照度和温度下降时，还观察到 Hsp60 水平进一步显着增加，表明细胞应激仍在进行中。与植物相关的微生物群落显示出植物区室和采样时间的差异，地上区室（叶子）比地下区室（根/根茎）更具活力。在叶际，观察到白天从主要由肠杆菌科组成的 Gammaproteobacteria 类的绝对优势到由于 Alphaproteobacteria 的兴起而增加生物多样性的逐渐转变。在地下，微生物多样性远低于地上，在所有采样时间内，伽马变形菌是最具代表性的类别。弧菌科在上午8:00和下午6:00最丰富，下午2:00略有减少，部分被Halomonadaceae取代。结合生化和微生物标记可以评估植物应激反应并加深对海草适应恶劣和不断变化的环境条件的了解，从而有助于检测生物体生理状态变化的早期迹象。此外，响应光和温度波动的 Hsp60 表达和相关细菌群落的变化支持“holobiont”理论，该理论将植物/微生物关联视为一个功能单位，如珊瑚所建议的那样。