Proteomic insights into growth-related molecular responses in the leaves of Para rubber seedlings (Hevea brasiliensis) treated with Bacillus cyclic lipopeptide extract and exogenous salicylic acid

Rubber trees (Hevea brasiliensis) are essential to industry but are highly vulnerable to diseases and environmental stress, particularly during the seedling stage in tropical climates. Growth-related molecular responses offer a sustainable strategy to enhance growth and stress tolerance while minimising chemical inputs. This study explored protein changes in rubber seedling leaves treated with a cyclic lipopeptide (CLP) extract obtained from Bacillus subtilis strain PTKU12 or exogenous salicylic acid (exogenous SA), with both treatments analysed relative to the control. Proteomic analysis revealed distinct protein expression patterns for each treatment. Protein clustering was assessed using partial least squares discriminant analysis, and unique proteins were identified through a Venn diagram. Functional annotation was performed using the Gene Ontology database, and protein interrelationships were visualised via a Sankey diagram. The CLP extract notably induced proteins involved in photosynthesis, oxidative phosphorylation, and secondary metabolite biosynthesis, which enhanced energy production, metabolic capacity, and structural integrity. Exogenous SA primarily affected proteins related to metabolic regulation and cellular signalling, indicating its role in rapid stress response. These findings highlight CLP extract from B. subtilis PTKU12 as an effective biostimulant, supporting molecular processes associated with growth-related metabolism and stress resilience in rubber seedlings while supporting the goals of sustainable agriculture.