Overexpression of McHB7 Transcription Factor from Mesembryanthemum crystallinum Improves Plant Salt Tolerance

Abstract

Mesembryanthemum crystallinum (common ice plant) is one of the facultative halophyte plants, and it serves as a model for investigating the molecular mechanisms underlying its salt stress response and tolerance. Here we cloned one of the homeobox transcription factor (TF) genes, McHB7, from the ice plant, which has 60% similarity with the Arabidopsis AtHB7. Overexpression of the McHB7 in Arabidopsis (OE) showed that the plants had significantly elevated relative water content (RWC), chlorophyll content, superoxide dismutase (SOD), and peroxidase (POD) activities after salt stress treatment. Our proteomic analysis identified 145 proteins to be significantly changed in abundance, and 66 were exclusively increased in the OE plants compared to the wild type (WT). After salt treatment, 979 and 959 metabolites were significantly increased and decreased, respectively, in the OE plants compared to the WT. The results demonstrate that the McHB7 can improve photosynthesis, increase the leaf chlorophyll content, and affect the TCA cycle by regulating metabolites (e.g., pyruvate) and proteins (e.g., citrate synthase). Moreover, McHB7 modulates the expression of stress-related proteins (e.g., superoxide dismutase, dehydroascorbate reductase, and pyrroline-5-carboxylate synthase B) to scavenge reactive oxygen species and enhance plant salt tolerance.

Bringing CAM photosynthesis to the table: Paving the way for resilient and productive agricultural systems in a changing climate

“…To fully elucidate a process such as CAM induction, it is therefore essential to study the epigenome. Furthermore, chromatin structure studies have proven to be effective in identifying cis -regulatory elements and transcription factors ( Lu et al., 2018 ; Farmer et al., 2021 ), which may play significant roles in triggering a photosynthetic switch to CAM ( Zhang et al., 2022b ). The introduction of single-cell assay for transposase-accessible chromatin using sequencing (scATAC-seq) methods ( Buenrostro et al., 2015 ; Lake et al., 2018 ; Lareau et al., 2019 ), as well as software packages to analyze the resulting data ( Fang et al., 2021 ), will pave the way for another promising avenue of CAM research and provide an opportunity to integrate data from different single-cell ’omics studies (e.g., histone post-translational modification [PTM] proteomics).…”

Defining Mechanisms of C3 to CAM Photosynthesis Transition toward Enhancing Crop Stress Resilience

“…HB7 was highly upregulated in both facultative CAM plants, T. triangulare [76] and M. crystallinum [19] in stress-induced CAM. Later functional studies showed that overexpression of the TF McHB7 in M. crystallinum [80] and A. thaliana [87] improved plant growth and salt tolerance. An ideal proposal for future CAM synthetic biology and engineering effort would be to enhance crop WUE and resilience (through stress-inducible promoters) without negatively affecting the yield so that crops can survive the drought and heat episodes and maintain productivity.…”

MdHB7‐like positively modulates apple salt tolerance by promoting autophagic activity and Na+ efflux

“…HD‐Zip TFs contain highly conserved HD and Zip domains (Ariel et al., 2007; Henriksson et al., 2005; Kim et al., 2007) and have been divided into four subfamilies (I–IV) (Ariel et al., 2007; Henriksson et al., 2005). Many studies in different species indicate that the HD‐Zip I group TFs are involved in the adaptation of plants to salt stress (Golldack et al., 2014; Sen et al., 2017; Wu et al., 2016; Yang & Guo, 2018b), such as the positive regulators ZmHDZ10 (Zhao et al., 2014), MtHB1 (Ariel et al., 2010), CaHDZ12 (Sen et al., 2017), and McHB7 (Zhang, Tan, et al., 2022), and the negative regulators JcHDZ07 (Tang et al., 2019), SIHB2 (Hu et al., 2017), MsHB7 (Li, Hou, et al., 2022), and ZmHDZ1 (Wang et al., 2017). The expression of the HD‐Zip I gene AtHB7 is up‐regulated by salt treatment in Arabidopsis (Henriksson & Henriksson, 2005; Soderman et al., 1994).…”