Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India.
Homi Bhabha National Institute, Anushaktinagar, Mumbai, India.
Plant Cell Environ. 2022 Oct;45(10):2972-2986. doi: 10.1111/pce.14412. Epub 2022 Aug 16.
In a striking similarity to plant chloroplasts, the cyanobacterium Anabaena displays very low catalase activity, but expresses several peroxiredoxins (Prxs), including the typical 2-Cys-Prx (annotated as Alr4641), that detoxify H O . Due to the presence of multiple Prxs, the precise contribution of Alr4641 to the oxidative stress response of Anabaena is not well-defined. To unambiguously assess its in vivo function, the Alr4641 protein was knocked down using the CRISPRi approach in Anabaena PCC 7120. The knockdown strain (An-KD4641), which showed over 85% decrease in the content of Alr4641, was viable, but grew slower than the control strain (An-dCas9). An-KD4641 showed elevated levels of reactive oxygen species and the expression of several redox-responsive genes was analogous to that of An-dCas9 subjected to oxidative stress. The knockdown strain displayed reduced filament size, altered thylakoid ultrastructure, a marked drop in the ratio of phycocyanin to chlorophyll a and decreased photosynthetic parameters compared to An-dCas9. In comparison to the control strain, exposure to H O had a more severe effect on the photosynthetic parameters or survival of An-KD4641. Thus, in the absence of adequate catalase activity, 2-Cys-Prx appears to be the principal Prx responsible for maintaining redox homoeostasis in diverse photosynthetic systems ranging from chloroplasts to cyanobacteria.
与植物叶绿体惊人相似，蓝藻鱼腥藻的过氧化氢酶活性非常低，但表达了几种过氧化物酶（Prx），包括典型的 2-Cys-Prx（注释为 Alr4641），可解毒 H2O2。由于存在多种 Prx，因此 Alr4641 对鱼腥藻氧化应激反应的确切贡献尚不清楚。为了明确评估其体内功能，使用 CRISPRi 方法在鱼腥藻 PCC 7120 中敲低 Alr4641 蛋白。敲低菌株（An-KD4641）的 Alr4641 含量降低了 85%以上，但仍具有活力，但其生长速度比对照菌株（An-dCas9）慢。An-KD4641 表现出更高水平的活性氧，并且几种氧化还原响应基因的表达与受到氧化应激的 An-dCas9 相似。与 An-dCas9 相比，敲低菌株的藻丝尺寸减小，类囊体超微结构改变，藻蓝蛋白与叶绿素 a 的比例明显下降，光合参数降低。与对照菌株相比，H2O2对 An-KD4641 的光合参数或存活率的影响更为严重。因此，在缺乏足够的过氧化氢酶活性的情况下，2-Cys-Prx 似乎是在从叶绿体到蓝藻等各种光合作用系统中维持氧化还原平衡的主要 Prx。
