Inverse modulation of the energy sensor Snf1‐related protein kinase 1 on hypoxia adaptation and salt stress tolerance in Arabidopsis thaliana

Abstract

Terrestrial plants are exposed to complex stresses of high salt-induced abscisic acid (ABA) and submergence-induced hypoxia when seawater floods fields. Many studies have investigated plant responses to individual stress conditions, but not so much for coupled or sequentially imposed stresses. We examined molecular regulatory mechanisms of gene expression underlying the cellular responses involved in crosstalk between salt and hypoxia stresses. Salt/ABA- and AtMYC2-dependent induction of a synthetic ABA-responsive element and the native RD22 promoters were utilized in our cell-based functional assays. Such promoter-based reporter induction was largely inhibited by hypoxia and hypoxia-inducible AKIN10 activity. Biochemical analyses showed that AKIN10 negatively modulates AtMYC2 protein accumulation via proteasome activity upon AKIN10 kinase activity-dependent protein modification. Further genetic analysis using transgenic plants expressing AKIN10 provided evidence that AKIN10 activity undermined AtMYC2-dependent salt tolerance. Our findings unravel a novel molecular interaction between the key signalling constituents leading crosstalk between salt and hypoxia stresses in Arabidopsis thaliana under the detrimental condition of submergence in saltwater.

The SnRK1 Kinase as Central Mediator of Energy Signaling between Different Organelles

“…Under osmotic stress conditions, ABA also controls the activity of the starch amylases BAM1 and AMY3 in leaves through the AREB/ ABF-SnRK2 kinase signaling pathway (Thalmann et al, 2016). Moreover, SnRK1 also has been identified as regulator of the MYC2 TF in the regulation of ABA-responsive elements (Im et al, 2014), and a further functional link between SnRK1 and ABA signaling was provided in a study of Suc responses in apple (Malus domestica), where the overexpression of the C2 domain ABA Insensitive Protein1 (MdCAIP1) was found to cause insensitivity toward ABA (Liu et al, 2017b). This phenotype was abolished in the presence of active MdSnRK1, which was shown to directly phosphorylate MdCAIP1 and thereby render it a target for 26S proteasomal degradation.…”

“…In a previous study, it was shown that AKIN10 overexpression resulted in decreased MYC2 protein levels, which could be counteracted by addition of proteasome inhibitor MG132. The authors demonstrated that AKIN10 and MYC2 physically interact, and identified the Ser that when phosphorylated is crucial for proteasomal degradation of MYC2 (Im et al, 2014).…”

“…SnRK1 activation also is triggered by hypoxia, leading to suppression of mitochondrial aerobic respiration resulting in cellular energy deprivation (Im et al, 2014;Cho et al, 2016). Flooding stress or hypoxia leads to a reduced availability of O 2 as the final electron acceptor in the mitochondrial electron transport chain (mETC), causing a rapid decrease in the cellular ATP:ADP ratio (Bailey-Serres and Voesenek, 2008).…”

Regulatory role of BOTRYTIS INDUCED KINASE1 in ETHYLENE INSENSITIVE3-dependent gene expression in Arabidopsis

“…Protein blot analysis followed a previously described method (Im et al 2014). The protoplast samples were incubated and collected, and then mixed with 59 sodium dodecyl sulfate (SDS) sample buffer.…”

Effects of fragmentation and seawater submergence on photochemical efficiency and growth in the clonal invader Carpobrotus edulis

“…Saltwater increase the concentration of Na + and Cl -in plant tissues, altering ionic ratios in plants and producing ion toxicity (Barrett-Lennard and Shabala, 2013;Grattan and Grieve, 1998;Rhoades et al, 1999). As a result, saltwater can have a negative impact on growth, compromising plant development and survival (Barrett-Lennard and Shabala, 2013;Im et al, 2014) Stolon connections allow clonal plants to be physiologically integrated (i.e. to shareresources between connected modules).…”