Abstract
Overexpression of finger millet calmodulin imparts drought and salt tolerance in plants. Drought and salinity are major environmental stresses which affect crop productivity and therefore are major hindrance in feeding growing population world-wide. Calcium (Ca2+) signaling plays a crucial role during the plant's response to these stress stimuli. Calmodulin (CaM), a crucial Ca2+sensor, is involved in transducing the signal downstream in various physiological, developmental and stress responses by modulating a plethora of target proteins. The role of CaM has been well established in the model plant Arabidopsis thaliana for regulating various developmental processes, stress signaling and ion transport. In the current study, we investigate the CaM of Eleusine coracana (common name finger millet, known especially for its drought tolerance and superior Ca2+ content). In-silico analysis showed that Eleusine CaM (EcCaM) has greater similarity to rice CaM as compared to Arabidopsis CaM due to the presence of highly conserved four EF-hand domains. To decipher the in-planta function of EcCaM, we have adopted the gain-of-function approach by generating the 35S::EcCaM over-expression transgenic in Arabidopsis. Overexpression of EcCaM in Arabidopsis makes the plant tolerant to polyethylene glycol (PEG) induced drought and salt stress (NaCl) as demonstrated by post-germination based phenotypic assay, ion leakage, MDA and proline estimation, ROS detection under stressed and normal conditions. Moreover, EcCaM overexpression leads to hypersensitivity toward exogenously applied ABA at the seed germination stage. These findings reveal that EcCaM mediates tolerance to drought and salinity stress. Also, our results indicate that EcCaM is involved in modulating ABA signaling. Summarizing our results, we report for the first time that EcCaM is involved in modulating plants response to stress and this information can be used for the generation of future-ready crops that can tolerate a wide range of abiotic stresses.
Highlights
Every year plants lose their growth and productivity due to various abiotic stresses, fluctuating temperature, a perturbation in soil water content, high salt salinity and others (Wang et al 2003: Arunanondchai et al 2018)
12 days old seedlings grown on 1⁄2 MS medium were transferred to 20% polyethylene glycol (PEG) and 200mM NaCl and samples were harvested with 0, 3 and 6 hrs Transgenic Arabidopsis plants, harbouring the Eleucine calmodulin (EcCaM) were grown on 1⁄2 MS medium containing 1% (w/v) sucrose and 0.8% (w/v) agar in growth room maintained at 22 ±20C and 60% relative humidity under a photoperiod of 16 h light and 8 h darkness
We identified a 450bp long EcCaM gene from the finger millet transcriptome using the rice CaM1 gene
Summary
Every year plants lose their growth and productivity due to various abiotic stresses, fluctuating temperature, a perturbation in soil water content, high salt salinity and others (Wang et al 2003: Arunanondchai et al 2018). Most plant reactions to stress stimuli leads to alteration in cellular calcium (Ca2+) concentration, which is termed as Ca2+ signatures (Pandey, 2008; Pandey and Sanyal, 2021). These Ca2+ signatures are sensed by several Ca2+ binding proteins divided into-Ca2+ sensors and Ca2+ sensor –relay proteins (Hashimoto and Kudla 2011; Ranty et al 2016). The majority of plant Ca2+ sensor proteins including calmodulins (CaMs), calmodulins-like proteins (CMLs), calcineurin B-like proteins (CBLs) and Ca2+-dependent protein kinases (CDPKs) contains acidic EF-hand Ca2+ binding motifs (DeFalco et al 2010; Mohanta et al 2019; Sanyal et al, 2019)
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