Quantitative Proteomics Reveals the Protein Regulatory Network of Anabaena sp. PCC 7120 under Nitrogen Deficiency

Anabaena sp. PCC 7120 (Anabaena 7120) is a photoautotrophic
filamentous cyanobacterium capable of
fixing atmospheric nitrogen. It is a model organism used for studying
cell differentiation and nitrogen fixation. Under nitrogen deficiency, Anabaena 7120 forms specialized heterocysts capable of nitrogen
fixation. However, the molecular mechanisms involved in the cyanobacterial
adaptation to nitrogen deficiency are not well understood. Here, we
employed a label-free quantitative proteomic strategy to systematically
investigate the nitrogen deficiency response of Anabaena 7120 at different time points. In total, 363, 603, and 669 proteins
showed significant changes in protein abundance under nitrogen deficiency
for 3, 12, and 24 h, respectively. With mapping onto metabolic pathways,
we revealed proteomic perturbation and regulation of carbon and nitrogen
metabolism in response to nitrogen deficiency. Functional analysis
confirmed the involvement of nitrogen stress-responsive proteins in
biological processes, including nitrogen fixation, photosynthesis,
energy and carbon metabolism, and heterocyst development. The expression
of 10 proteins at different time points was further validated by using
multiple reaction monitoring assays. In particular, many dysregulated
proteins were found to be time-specific and involved in heterocyst
development, providing new candidates for future functional studies
in this model cyanobacterium. These results provide novel insights
into the molecular mechanisms of nitrogen stress responses and heterocyst
development in Anabaena 7120.

Anabaena sp. PCC 7120（7120型蓝藻）是一种光合自养性丝状蓝细菌，具备大气氮的固定能力。该物种作为研究细胞分化和氮固定的模式生物而被广泛应用。在氮缺乏条件下，7120型蓝藻能够形成具有氮固定能力的特殊异形胞。然而，涉及蓝细菌适应氮缺乏的分子机制尚不明确。本研究中，我们采用无标记定量蛋白质组学策略，系统地研究了7120型蓝藻在不同时间点对氮缺乏的响应。具体而言，在氮缺乏条件下3小时、12小时和24小时后，分别有363种、603种和669种蛋白质在蛋白丰度上发生了显著变化。通过代谢途径映射，我们揭示了蛋白质组在应对氮缺乏时的扰动和调控，特别是在碳氮代谢方面。功能分析证实了氮胁迫响应蛋白在包括氮固定、光合作用、能量和碳代谢以及异形胞发育在内的生物过程中的参与。此外，通过多反应监测实验进一步验证了10种在不同时间点表达的蛋白质。特别是，许多失调蛋白被发现具有时间特异性，并参与异形胞发育，为该模式蓝细菌未来的功能研究提供了新的候选基因。这些研究结果为Anabaena 7120中氮胁迫响应和异形胞发育的分子机制提供了新的见解。