Sporulation is a microbial adaptive strategy to resist inhospitable conditions for vegetative growth and to disperse to colonise more favourable environments. This microbial trait is widespread in Actinobacteria. Among them, Frankia strains are able to differentiate sporangia in pure culture, while others can sporulate even when in symbiosis with sporulation occurring within host cells. The molecular determinants controlling Frankia sporulation have not been yet described. In order to highlight, for the first time, the molecular players potentially involved in Frankia sporulation, we conducted (i) a comparison of protein contents between Frankia spores and hyphae and (ii) a comparative genomic analysis of Frankia proteomes with sporulating and non-sporulating Actinobacteria. Among the main results, glycogen-metabolism related proteins, as well as oxidative stress response and protease-like proteins were overdetected in hyphae, recalling lytic processes that allow Streptomyces cells to erect sporogenic hyphae. Several genes encoding transcriptional regulators, including GntR-like, appeared up-regulated in spores, as well as tyrosinase, suggesting their potential role in mature spore metabolism. Finally, our results highlighted new proteins potentially involved in Frankia sporulation, including a pyrophosphate-energized proton pump and YaaT, described as involved in the phosphorelay allowing sporulation in Bacillus subtilis, leading us to discuss the role of a phosphorelay in Frankia sporulation.

中文翻译：

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比较基因组学和蛋白质组学突出显示了参与Frankia孢子形成的关键分子。

孢子形成是一种微生物适应性策略，可以抵抗营养生长的不利条件，并分散到更有利的环境中定殖。这种微生物特征在放线菌中普遍存在。其中，Frankia菌株能够在纯培养物中区分孢子囊，而其他菌株甚至在与宿主细胞内发生孢子形成共生时也能形成孢子。尚未描述控制Frankia孢子形成的分子决定簇。为了首次突显潜在参与Frankia孢子形成的分子，我们进行了（i）Frankia孢子和菌丝之间蛋白质含量的比较，以及（ii）Frankia蛋白质组具有孢子形成和非孢子形成的比较基因组分析放线放线菌。在主要结果中，糖原代谢相关蛋白，以及在菌丝中过度检测到氧化应激反应和蛋白酶样蛋白，回想起允许链霉菌细胞竖立孢子菌丝的裂解过程。几个编码转录调节因子的基因，包括GntR-like，在孢子以及酪氨酸酶中均被上调，表明它们在成熟孢子代谢中的潜在作用。最后，我们的结果强调了可能参与Frankia孢子形成的新蛋白，包括焦磷酸激发的质子泵和YaaT，它们被描述为参与枯草芽孢杆菌中的孢子形成，从而使我们讨论了Franke孢子形成中磷的作用。几个编码转录调节因子的基因，包括GntR-like，在孢子以及酪氨酸酶中均被上调，表明它们在成熟孢子代谢中的潜在作用。最后，我们的结果强调了可能参与Frankia孢子形成的新蛋白，包括焦磷酸激发的质子泵和YaaT，它们被描述为参与枯草芽孢杆菌中的孢子形成，从而使我们讨论了Franke孢子形成中磷的作用。几个编码转录调节因子的基因，包括GntR-like，在孢子以及酪氨酸酶中均被上调，表明它们在成熟孢子代谢中的潜在作用。最后，我们的结果强调了可能参与Frankia孢子形成的新蛋白，包括焦磷酸激发的质子泵和YaaT，它们被描述为参与枯草芽孢杆菌中的孢子形成，从而使我们讨论了Franke孢子形成中磷的作用。