Figure 1: Schematic diagram showing the heavy metal’s ROS signaling of the MAPKs cascade and a possible pipeline to identifying and elucidating more key players in this pathway.
Conclusion
Heavy metals do not decompose in the soil, and therefore poses a major threat to plant growth and development (Rashid et al., 2023). HM toxicity becomes more evident when their concentrations exceed threshold levels (Table 1 ) within the soil (Rashid et al., 2023). ROS production and alteration in plant’s redox state is a shared response among heavy metal stresses (Singh et al., 2019). Overaccumulation of ROS has been shown to be detrimental to plant development; however, plants have adapted signaling pathways to which the perceived stress signal is sent to the nucleus for an appropriate response (Singh et al., 2019). While there has been much research conducted on HMs and plants adaptive mechanisms, there has been a knowledge gap between signaling pathways and how individual HM-ROS signals interact and activate a particular signaling pathway, the MAPK pathway and further how activation of MAPKs triggers a downstream activation of transcription factors to impart resistance against HM-stress.
In animals MAPKs regulatory network has been extensively studied under heavy metal stress, more so than in plants, therefore, it will be greatly beneficial to investigate the importance of MAPKs crosstalk in heavy metal stress in plants. Limited investigations report on the regulatory network of MAPKs with transcription factors, therefore indicates towards the need for more in depth experiments in response to heavy metals in plants. In this review, the influence of HM-ROS on the activation of MAPKs along with transcription factors are reported. Numerous studies across various scientific groups assisted to elucidate that various HM do indeed instigate the production of ROS which interplay with MAPK to induce a stress response. Furthermore, this review delved into the downstream transcription factors (WRKY, bZIP, MYB and HSF) that are activated to highlight particular stress responses (detoxification, HM-uptake, HM-transport, and growth and development) under various HM-stresses. The pipeline proposed in Section 4and Figure 1 indicates an approach to assist in bridging the gap between HM-ROS induced MAPK and the downstream transcription factors activated. Hence, the purpose is to confirm the functional roles of MAPK genes, and the transcription factors and their regulation by ROS signaling to develop heavy metal resistance plants.
Author Contributions : This work was supported by the National Research Foundation of South Africa (NRF)This research was financially supported by the NRF to M.K and A.K (Grant numbers: 107023, 115280, 116346 and 109083), A.G. (Grant number: 129493), A.G. was also supported by the CRF fund of the University of the Free State.
Acknowledgements including funding information : This work was supported by the National Research Foundation of South Africa (NRF)This research was financially supported by the NRF to A.K. and M.K. (Grant numbers: 107023, 115280, 116346 and 109083), A.G. (Grant number: 129493). A.G. was also supported by the CRF fund of the University of the Free State.
Conflict of Interest: The authors declare that there are no conflicts of interest.
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