Proteomics of Homeobox7 Enhanced Salt Tolerance in Mesembryanthemum crystallinum

Abstract

Mesembryanthemum crystallinum (common ice plant) is a halophyte species that has adapted to extreme conditions. In this study, we cloned a McHB7 transcription factor gene from the ice plant. The expression of McHB7 was significantly induced by 500 mM NaCl and it reached the peak under salt treatment for 7 days. The McHB7 protein was targeted to the nucleus. McHB7-overexpressing in ice plant leaves through Agrobacterium-mediated transformation led to 25 times more McHB7 transcripts than the non-transformed wild type (WT). After 500 mM NaCl treatment for 7 days, the activities of superoxide dismutase (SOD) and peroxidase (POD) and water content of the transgenic plants were higher than the WT, while malondialdehyde (MDA) was decreased in the transgenic plants. A total of 1082 and 1072 proteins were profiled by proteomics under control and salt treatment, respectively, with 22 and 11 proteins uniquely identified under control and salt stress, respectively. Among the 11 proteins, 7 were increased and 4 were decreased after salt treatment. Most of the proteins whose expression increased in the McHB7 overexpression (OE) ice plants under high salinity were involved in transport regulation, catalytic activities, biosynthesis of secondary metabolites, and response to stimulus. The results demonstrate that the McHB7 transcription factor plays a positive role in improving plant salt tolerance.

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

“…In our study, many significantly salt-regulated proteins were annotated to be involved in photosynthesis and chlorophyll biosynthetic process. These results are consistent with the previous study on McHB7 in the ice plant, which showed the salt-induced proteins were related to the light-harvesting complex [ 28 ]. All the results point to the conclusion that overexpression of McHB7 in plants can promote and modulate the expression of photosynthesis-related proteins under salt stress conditions, hence contributing to the growth and development of plants when exposed to adverse environmental conditions.…”

“…SOD and POD are usually considered as antioxidant enzymes for ROS scavenging, thus contributing to alleviating the harmful effects of ROS such as O 2 - and H 2 O 2 [ 47 ]. McHB7 -OE plants showed higher activities of SOD and POD under salt stress conditions, as is consistent with the previous study in the ice plant that transgenic plants had significantly higher SOD and POD compared to WT when treated with salt stress [ 28 ]. These results suggest that McHB7 plays a positive role in salt stress response through ROS removal.…”

“…The cDNA template and primers F2 and R2 were used for PCR detection, and the recombinant plasmid McHB7 -pCAMBIA1300 and WT Arabidopsis were used as positive and negative control, respectively. To test the protein levels, 0.1 g fresh leaves of three-week-old Arabidopsis were ground into powder and immersed into 500 μL protein extraction buffer (150 mM NaCl, 50 mM Tri-HCl, 1 mM EDTA, 1% Triton X-100, and 1 × protease cocktail) at 4 °C for 1 h. The supernatant was collected by centrifugation, at the speed of 10,000 rpm for 10 min, and used as crude protein extraction for Western blot, as previously described [ 28 ]. WT was used as negative control.…”

“…Based on our previous transcriptomic study on ice plants under salt stress [ 27 ], a McHB7 was significantly upregulated after 500 mM NaCl treatment for seven days. In another study [ 28 ], we cloned the nuclear-localized gene McHB 7 from the ice plant. Transient expression of the McHB7 in ice plants effectively improved plant salt tolerance.…”

The first released available genome of the common ice plant (Mesembryanthemum crystallinum L.) extended the research region on salt tolerance, C3-CAM photosynthetic conversion, and halophilism

“…Recently, the molecular processes underlying these phenomena have been elucidated at the levels of transcription, post-transcription ( Taybi and Cushman 1999 ; Zhang et al 2021 ), translation, post-translation ( Forsthoefel et al 1995 ; Nimmo 2000 ), specific proteins (tonoplast and plasma-membrane H(+)-ATPases: Vera-Estrella et al 1999 ; glucose 6-phosphate/phosphate translocator: Kore-eda et al 2013 ; ions transporter and compatible solute synthase: Tran et al 2020a ), mitochondria, and chloroplasts ( Tran et al 2020b ; Niewiadomska and Pilarska 2021 ). Also, high-throughput gene expression profiling has been conducted using expression sequence tags (ESTs) ( Kore-eda et al 2004 ), microarrays ( Cushman et al 2008 ), and next generation sequencing (NGS; Oh et al 2015 ; Tsukagoshi et al 2015 ; Chiang et al 2016 ; Kong et al 2020 ).…”