Overexpression of Karrikins Receptor Gene Sapium sebiferum KAI2 Promotes the Cold Stress Tolerance via Regulating the Redox Homeostasis in Arabidopsis thaliana.

Faheem Afzal Shah,Ruyue Wei,Jun Ni,Yuanyuan Yao,Hao Hu,Lifang Wu

doi:10.3389/fpls.2021.657960

Faheem Afzal Shah, Ruyue Wei + Show 4 more

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https://doi.org/10.3389/fpls.2021.657960

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Abstract

KARRIKINS INSENSITIVE2 (KAI2) is the receptor gene for karrikins, recently found to be involved in seed germination, hypocotyl development, and the alleviation of salinity and osmotic stresses. Nevertheless, whether KAI2 could regulate cold tolerance remains elusive. In the present study, we identified that Arabidopsis mutants of KAI2 had a high mortality rate, while overexpression of, a bioenergy plant, Sapium sebiferum KAI2 (SsKAI2) significantly recovered the plants after cold stress. The results showed that the SsKAI2 overexpression lines (OEs) had significantly increased levels of proline, total soluble sugars, and total soluble protein. Meanwhile, SsKAI2 OEs had a much higher expression of cold-stress-acclimation-relate genes, such as Cold Shock Proteins and C-REPEAT BINDING FACTORS under cold stress. Moreover, the results showed that SsKAI2 OEs were hypersensitive to abscisic acid (ABA), and ABA signaling genes were w significantly affected in SsKAI2 OEs under cold stress, suggesting a potential interaction between SsKAI2 and ABA downstream signaling. In SsKAI2 OEs, the electrolyte leakage, hydrogen peroxide, and malondialdehyde contents were reduced under cold stress in Arabidopsis. SsKAI2 OEs enhanced the anti-oxidants like ascorbate peroxidase, catalase, peroxidase, superoxide dismutase, and total glutathione level under cold stress. Conclusively, these results provide novel insights into the understanding of karrikins role in the regulation of cold stress adaptation.

Highlights

Plants are the sessile organisms which often exposed to a broad range of adverse environmental conditions
The results showed that the expression of KARRIKINS INSENSITIVE2 (KAI2) in Sapium sebiferum was increased under cold stress (4◦C), salinity (200 mM NaCl), and osmotic stress (300mM mannitol) as compared to control condition (Figures 1B–D)
A few studies have reported the involvement of KAI2 in the mitigation of environmental stresses such as osmotic and salinity in Arabidopsis, but there was not report regarding the role of karrikins-KAI2 in the regulation of cold stress

Summary

Introduction

Plants are the sessile organisms which often exposed to a broad range of adverse environmental conditions. Among a large number of adverse conditions, cold (chilling and freezing) stress significantly limit crop growth and agricultural productivity. Cold acclimation enhances the endogenous as well as inducible components accumulation. The endogenous components, which promote cold tolerance, have extensively been studied and mainly refer to metabolites with anti-oxidant activity (Winkel-Shirley, 2002), with hormonal responses (Eremina et al, 2016) or osmoprotective functions to limit ice nucleation and to overcome the freeze-induced dehydration inside the plant cells (Janská et al, 2010). Other regulatory molecules such as polyamines, reactive oxygen species, nitric oxide have been described to be involved in cold tolerance (Cuevas et al, 2008; Zhao et al, 2009; Puyaubert and Baudouin, 2014; van Buer et al, 2016)

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