How Plant Signals Balance Medicine Production and Salt Tolerance in Sage

Jenn Hoskins
15th September, 2024

How Plant Signals Balance Medicine Production and Salt Tolerance in Sage

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Northwest A&F University studied the role of stress-associated proteins (SAPs) in Salvia miltiorrhiza's response to stress and metabolism
  • The gene SmSAP4 was significantly upregulated under methyl jasmonate (MeJA) and salt stress, increasing tanshinones and decreasing salvianolic acids
  • Overexpressing SmSAP4 reduced salt stress tolerance in both Arabidopsis thaliana and S. miltiorrhiza, affecting antioxidant enzyme activity and sodium-potassium balance
Salvia miltiorrhiza, a plant of significant traditional Chinese medicinal value, has been the focus of a recent study conducted by researchers at Northwest A&F University[1]. The study aimed to explore the role of stress-associated proteins (SAPs) in the plant's response to various stresses and its metabolic processes. SAPs are known for their involvement in regulating plant growth, development, and responses to both biotic (living factors) and abiotic (non-living factors) stress. These proteins are characterized by A20/AN1 zinc finger structural domains, which are crucial for their function. The research team performed a comprehensive genome-wide identification of the SAP gene family in S. miltiorrhiza. Their expression analysis revealed that one particular gene, SmSAP4, was significantly upregulated when the plant was subjected to methyl jasmonate (MeJA) and salt stress. Methyl jasmonate is a plant hormone that plays a role in stress responses, while salt stress is a common abiotic stress that affects plant health. To understand the functional role of SmSAP4, the researchers overexpressed this gene in S. miltiorrhiza hairy roots. This genetic modification led to an increased content of tanshinones, compounds known for their medicinal properties, and a decreased content of salvianolic acids, another group of bioactive compounds. Conversely, silencing SmSAP4 using RNA interference (RNAi) had the opposite effect, reducing tanshinones and increasing salvianolic acids. Interestingly, overexpressing SmSAP4 in both Arabidopsis thaliana (a model plant) and S. miltiorrhiza hairy roots resulted in decreased tolerance to salt stress. This was evidenced by increased activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), which are typically involved in mitigating oxidative stress. Additionally, these plants showed a reduced ability to maintain a balanced sodium (Na+) to potassium (K+) ratio, which is critical for cellular function under salt stress conditions. Further investigations revealed a complex regulatory mechanism involving SmSAP4. The study found that MeJA alleviated the inhibitory effect of another protein, SmJAZ3, on SmSAP4 activation by two transcription factors, SmbHLH37 and SmERF73. However, MeJA did not affect the inhibition of SmSAP4 activation by SmJAZ8 through SmbHLH37. This indicates a sophisticated interaction network where different proteins and hormones modulate the expression and activity of SmSAP4. These findings align with earlier studies on the role of SAPs in stress responses. For instance, overexpression of the Medicago truncatula SAP gene (MtSAP1) in tobacco plants has been shown to enhance tolerance to temperature, osmotic, and salt stresses[2]. This earlier research also indicated that MtSAP1 overexpression led to higher nitric oxide (NO) production, a signaling molecule involved in stress responses, which contributed to better stress tolerance[3]. However, unlike MtSAP1, which did not affect proline accumulation, an important stress-related metabolite[2], SmSAP4 appears to influence the balance of different secondary metabolites, such as tanshinones and salvianolic acids, under stress conditions. The study from Northwest A&F University provides valuable insights into the role of SAPs in plant stress responses and secondary metabolism. By elucidating the regulatory mechanisms involving SmSAP4, the research opens up new possibilities for genetic manipulation to enhance stress tolerance and optimize the production of valuable medicinal compounds in S. miltiorrhiza. This could have significant implications for agriculture and the pharmaceutical industry, particularly in the context of increasing environmental stresses and the demand for plant-based medicines.

MedicineBiochemPlant Science

References

Main Study

1) SmJAZs-SmbHLH37/SmERF73-SmSAP4 module mediates jasmonic acid signaling to balance biosynthesis of medicinal metabolites and salt tolerance in Salvia miltiorrhiza.

Published 12th September, 2024

https://doi.org/10.1111/nph.20110

Related Studies

2) Medicago truncatula stress associated protein 1 gene (MtSAP1) overexpression confers tolerance to abiotic stress and impacts proline accumulation in transgenic tobacco.

https://doi.org/10.1016/j.jplph.2013.01.008

3) Overexpression of a Medicago truncatula stress-associated protein gene (MtSAP1) leads to nitric oxide accumulation and confers osmotic and salt stress tolerance in transgenic tobacco.

https://doi.org/10.1007/s00425-012-1635-9


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