Exploring effectiveness of salicylic acid and methyl jasmonate elicitors in influencing growth performance, epigenetic regulation, gene transcription, and secondary metabolism in pepper (Capsicum annuum): an in vitro biological assessment.

Epigenetic responses of in vitro-cultured plants to elicitation with salicylic acid (SA) and methyl jasmonate (MJ) have been little explored. This study addresses how pepper seedlings respond to incorporating SA (0 and 10 µM) and/or MJ (0 and 10 µM) into the culture medium at physiological and molecular levels. The individual application of MJ or SA enhanced root fresh weight by an average of 59.8%. However, the mixed treatment synergistically augmented the root biomass by 2.2-fold. SA was individually more effective than MJ in triggering changes in the DNA methylome profiles. The epigenetic cytosine methylation in the MJ + SA group differed from that of the individual treatments. The individual SA treatment led to severe DNA hypermethylation, which was modified with the MJ application. Moreover, MJ and/or SA-mediated upregulation of the histone deacetylase (HDA) gene also confirmed the epigenetic regulation at the histone modification level. The MJ elicitor showed greater effectiveness in influencing the transcription of the target genes than the SA one. The expression of the MAPK kinase and ethylene-responsive transcription factor (EREB) genes displayed a similar upward trend. Applying pepper seedlings with MJ and SA increased proline concentrations and catalase activities. The simultaneous application of MJ and SA supplements effectively stimulated secondary metabolism, indicated by increased soluble phenols and activity of the phenylalanine ammonia-lyase enzyme. This study presents novel comparative insights into the SA and MJ-mediated epigenetic modifications. These findings can be employed to design in vitro culture systems and implement large-scale projects.