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Mechanisms of Bacterial Heavy Metal Resistance and Homeostasis
Published in Edgardo R. Donati, Heavy Metals in the Environment, 2018
Pallavee Srivastava, Meenal Kowshik
Magnesium transporters of the P-type ATPase family such as Mgt A/B and Mgt E, involved in Mg2+ import in various bacteria (Smith and Maguire, 1998), are regulated by a Mg-responsive riboswitch, M-box. In Salmonella, expression of mgtA and mgtB is under the control of metalloregulatory proteins PhoQ (membrane bound sensor kinase) and PhoP (transcriptional regulator) (Garcia et al., 1996), as well as post-transcriptional regulation through M-box (Fig. 4a). This M-box resides within the 5’UTR region of mgtA in Salmonella enterica (Cromie et al., 2006) and upstream of mgtE gene in Bacillus subtilis (Dann III et al., 2007). Under low Mg conditions, the magnesium responsive riboswitch of S. enterica undergoes conformational changes that favor transcription elongation, while in presence of excess Mg, the alternative conformation prevents transcription of downstream genes (Cromie et al., 2006). Similarly, the B. subtilis M-box RNA acts as an ‘off’ switch in the presence of excess Mg decreasing the expression of downstream genes (Fig. 4b). The Mg2+ binds to the most highly conserved region present within the Mg2+ sensing aptamer domain. Binding of Mg2+ to this aptamer domain stabilizes the conformation to form a compacted RNA by a suite of long-range base interactions that render a stretch of nucleotides inaccessible for the formation of the anti-terminator helix. This allows the formation of downstream intrinsic transcription terminator, thus preventing expression of downstream genes (Dan III et al., 2007).
The aluminum tolerance and detoxification mechanisms in plants; recent advances and prospects
Published in Critical Reviews in Environmental Science and Technology, 2022
Lei Yan, Muhammad Riaz, Jiayou Liu, Min Yu, Jiang Cuncang
Secondly, several functional genes related to Al tolerance have been discovered and identified such as ASR5 (Abscisic acid, stress and ripening) or OsMGT1 (Magnesium Transporter). However, the direct relationship between these genes and Al resistance and the specific mechanism still need to be studied. In the future, more attention should be focused on the genomics, proteomics, transcriptomics level to explore more genes related to Al tolerance including the ASR5 and OsMGT1, and reveal the expression patterns of these genes in different plants and their functions of resistance to Al toxicity. Besides, the research of transgenic technology can be strengthened in the later stage, and established the transgenic safety evaluation and detection system, and widely used in commercial production, which may help to fundamentally clarify the mechanism of improving the transportation and resistance to Al in plants.