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（安巴纳菌7120）为一种光合自养性丝状蓝藻，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过程的模式生物而被广泛应用。在氮缺乏条件下，安巴纳菌7120能够形成具有氮固定能力的特化异形胞。然而，涉及蓝藻适应氮缺乏的分子机制尚不明确。在本研究中，我们采用无标记定量蛋白质组学策略，系统性地探究了安巴纳菌7120在不同时间点对氮缺乏的响应。具体而言，在3小时、12小时和24小时的氮缺乏条件下，分别有363、603和669种蛋白质在蛋白质丰度上发生了显著变化。通过对代谢途径的映射，我们揭示了蛋白质组在响应氮缺乏时对碳和氮代谢的扰动和调控。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学过程中的参与。此外，通过多重反应监测法进一步验证了不同时间点10种蛋白质的表达。特别是，许多失调的蛋白质被发现具有时间特异性，并参与异形胞的发育，为该模式蓝藻未来的功能研究提供了新的候选基因。这些研究结果为安巴纳菌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。