Stress proteomics on the application of defense hormones in swietenia macrophylla king seedlings

Abstract

Climate change poses severe challenges to ecosystems, agriculture, and forestry by intensifying extreme weather events like droughts, floods, and heat waves, compromising plant health, productivity, and ecosystem stability. Additionally, climate induced salinity stress, driven by rising sea levels and increased irrigation, disrupts plant water and nutrient absorption, stunts root growth, and causes ion toxicity, reducing forest productivity, especially in tropical and subtropical regions. In response to these stresses, plants activate intricate defense mechanisms that mitigate damage and facilitate adaptation to adverse conditions. The defense hormones like Jasmonic Acid (JA) and Salicylic Acid (SA) play a vital role in enhancing plant resilience by regulating the expression of stress-related genes, promoting the production of protective proteins, and initiating physiological adjustments that optimize water-use efficiency and sustain cellular balance. This study investigated the effects of defense hormones, JA and SA, on mahogany seedlings, a species valued for its rapid growth, high-quality wood, workability, and durability. The research aimed to understand the role of JA and SA in alleviating drought and salinity stress and explore the associated stress proteomics, offering valuable insights into adaptive responses and resilience of mahogany seedlings to abiotic stress. The effects of various concentrations of JA and SA on the growth and development of six-month-old mahogany seedlings were investigated. Seedlings were treated with foliar applications of JA and SA at six different concentrations (0.2 mM, 0.4 mM, 0.6 mM, 0.8 mM, 1 mM and control), with measurements taken every 30 days over a 150-day period. The results indicated that JA at 0.6 mM (T4) and SA at 0.8 mM (T5) were the most effective treatments, leading to optimal growth performance. These treatments significantly enhanced overall plant vigor, promoting stability as indicated by the sturdiness quotient and improving seedling quality. The findings demonstrate the potential of JA and SA in enhancing mahogany growth, particularly under stress conditions, highlighting their promising applications in forestry practices. xviii The effectiveness of JA and SA in alleviating drought and salinity stress in mahogany seedlings was thoroughly examined. Drought stress was induced by withholding irrigation until wilting, while salinity stress was applied using a 100 mM NaCl solution (EC = 6 dS/m) over four days. Following stress induction, JA and SA were applied to leaves to enhance acclimatization and recovery, with measurements taken under normal, stressed, and 8-day post-hormone application conditions. Results indicated that JA at 0.6 mM significantly enhanced leaf retention and shoot production under drought and salinity stress conditions. It also improved photosynthetic rates and chlorophyll pigments during recovery compared to control seedlings. In contrast, control seedlings demonstrated higher proline accumulation during recovery from both stress types than those treated with SA and JA. The defense hormone JA at 0.6 mM is highly effective in alleviating drought and salinity stress, while SA (0.8 mM) was particularly effective against drought stress. Both hormones significantly influenced morphological, physiological, and biochemical adaptations in response to stress. A comparative proteomic analysis of mahogany seedlings was performed under normal, stress, and recovery conditions (48 hours post-hormone application). Results indicated that JA (0.6 mM) significantly influenced protein expression, effectively mitigating drought and salinity stress, while SA (0.8 mM) was particularly effective against drought stress. Each stress condition produced unique protein expression profiles, reflecting hormone-specific responses. Key proteins identified included Heat Shock Proteins and Heat Stress Transcription Factor 4a for drought stress, and Cation/H⁺ Antiporter and Guanine Nucleotide-Binding Protein for salinity stress, emphasizing their roles in enhancing stress resilience and recovery. xix