Overexpression of the sorghum transcription factor SbNAC074 enhances plant salt tolerance by promoting proline accumulation, boosting antioxidant enzyme activity, and interacting with SbMPK3 for phosphorylation-mediated regulation.

Keywords: Phosphorylate, Salt stress, SbMPK3, SbNAC074, Sorghum

Salt stress poses a major challenge to plant productivity by disrupting osmotic balance and generating reactive oxygen species (ROS). Transcription factors (TFs) from the NAC family are known to play vital roles in mitigating such stresses. Scientists from Guizhou Normal University investigated the sorghum NAC transcription factor SbNAC074 and found it to be highly responsive to salt stress, conferring improved tolerance when overexpressed in transgenic tobacco. These plants exhibited elevated proline levels, a key osmoprotectant, and decreased malondialdehyde (MDA) content, indicating reduced membrane damage. Additionally, SbNAC074 overexpression enhanced the activities of ROS-scavenging enzymes—superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)—and significantly lowered hydrogen peroxide (H₂O₂) accumulation. These findings underscore the multifunctional role of SbNAC074 in protecting plants from salinity-induced oxidative stress through osmotic adjustment and improved antioxidant capacity.

Further investigation revealed that SbNAC074 physically interacts with and is phosphorylated by SbMPK3, a mitogen-activated protein kinase (MAPK) previously associated with enhanced salt tolerance in sorghum. MAPK-mediated phosphorylation is known to regulate the stability and activity of various TFs under stress. Consistent with this, the phosphorylation of SbNAC074 by SbMPK3 is hypothesized to enhance its stability and function, thereby contributing to the observed improvements in stress resilience. Together, these results highlight a coordinated regulatory mechanism involving NAC TFs and MAPKs that modulates salt stress responses through transcriptional regulation, ROS detoxification, and ion homeostasis—offering potential targets for genetic strategies to improve crop salt tolerance.

SorghumBase examples: 

SbNAC074 (SORBI_3005G188000)

SbMPK3 (SORBI_3001G410100)

Figure 1: The Expression tab of the SorghumBase genes search interface for the SbNAC074 TF (SORBI_3005G188000) shows it is expressed almost exclusively in seed tissue under normal conditions.
Figure 2: Expression profile of SbNAC074 (SORBI_3005G188000) in Sorghum bicolor BTx623 from the SorghumBase eFP browser. The heatmap illustrates tissue-specific expression of SbNAC074, a NAC transcription factor linked to salt stress response. Expression levels across major tissues bundle sheath, leaf mesophyll, flag leaf, inflorescence, seed, spikelet, and stem are shown using a color scale where red indicates high expression. Notably, SbNAC074 is predominantly expressed in developing seed tissues, supporting its regulatory role in stress and developmental processes.
Figure 3: Search for MPK3 shows hits to ATMAPK3 in Arabidopsis thaliana which shows close homolog  to the gene model SORBI_3001G410100, which is located on chromosome 1 of the BTx623 genome and under pathways view SORBI_3001G410100 (blue node) downstream of the auxin–ERF2 module and upstream of MAPK6/MKK5, mirroring the canonical MAPK cascade. In the present study, SbMPK3 (the sorghum MPK3 ortholog) phosphorylates the NAC transcription factor SbNAC074 to activate salt-stress responses; this pathway-level conservation underscores how SbMPK3 integrates hormonal and stress signals in sorghum.
Reference:

Wang H, Wei L, Yu F, Zeng T, Gu L, Zhu B, Du X. The sorghum SbMPK3-SbNAC074 module involved in salt tolerance. Plant Physiol Biochem. 2025 Jul;224:109981. PMID: 40327899. doi: 10.1016/j.plaphy.2025.109981. Read more

SbNAC074 Enhances Salt Tolerance via Proline Accumulation, Antioxidant Activity, and MAPK-Mediated Regulation

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