Srivastava Akanksha, Kumar Arvind, Biswas Subhankar, Srivastava Vaibhav, Rajaram Hema, Mishra Yogesh
Department of Botany, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.
Biochim Biophys Acta Proteins Proteom. 2023 May 1;1871(3):140902. doi: 10.1016/j.bbapap.2023.140902. Epub 2023 Jan 27.
LexA, a well-characterized transcriptional repressor of SOS genes in heterotrophic bacteria, has been shown to regulate diverse genes in cyanobacteria. An earlier study showed that LexA overexpression in a cyanobacterium, Anabaena sp. PCC7120 reduces its tolerance to Cd stress. This was later shown to be due to modulation of photosynthetic redox poising by LexA under Cd stress. However, due to the global regulatory nature of LexA and the prior prediction of AnLexA-box in a few heavy metal-responsive genes, we speculated that LexA has a broad role in Cd tolerance, with regulation over a variety of Cd stress-responsive genes in addition to photosynthetic genes. Thus, to further expand the knowledge on the regulatory role of LexA in Cd stress tolerance, a cytosolic proteome profiling of Anabaena constitutively overexpressing LexA upon Cd stress was performed. The proteomic study revealed 25 differentially accumulated proteins (DAPs) in response to the combined effect of LexA overexpression and Cd stress, and the other 11 DAPs exclusively in response to either LexA overexpression or Cd stress. The 36 identified proteins were related with a variety of functions, including photosynthesis, C-metabolism, antioxidants, protein turnover, post-transcriptional modifications, and a few unknown and hypothetical proteins. The regulation of LexA on corresponding genes, and six previously reported Cd efflux transporters, was further validated by the presence of AnLexA-boxes, transcript, and/or promoter analyses. In a nutshell, this study identifies the regulation of Anabaena LexA on several Cd stress-responsive genes of various functions, hence expanding the regulatory role of LexA under Cd stress.
LexA是异养细菌中SOS基因一个已被充分表征的转录阻遏物，已被证明可调控蓝藻中的多种基因。一项早期研究表明，在蓝藻鱼腥藻属PCC7120中过表达LexA会降低其对镉胁迫的耐受性。后来发现这是由于在镉胁迫下LexA对光合氧化还原平衡的调节所致。然而，由于LexA的全局调节性质以及在一些重金属响应基因中先前对AnLexA-box的预测，我们推测LexA在镉耐受性中具有广泛作用，除了光合基因外，还对多种镉胁迫响应基因进行调控。因此，为了进一步扩展关于LexA在镉胁迫耐受性中调节作用的知识，我们对在镉胁迫下组成型过表达LexA的鱼腥藻进行了胞质蛋白质组分析。蛋白质组学研究揭示了25种差异积累蛋白（DAPs）是对LexA过表达和镉胁迫共同作用的响应，另外11种DAPs仅对LexA过表达或镉胁迫作出响应。鉴定出的这36种蛋白质与多种功能相关，包括光合作用、碳代谢、抗氧化剂、蛋白质周转、转录后修饰以及一些未知和假设的蛋白质。通过AnLexA-box的存在、转录本和/或启动子分析，进一步验证了LexA对相应基因以及六个先前报道的镉外排转运蛋白的调控。简而言之，本研究确定了鱼腥藻LexA对多种功能的几个镉胁迫响应基因的调控，从而扩展了LexA在镉胁迫下的调节作用。
