ASHS 2025 Conference

Chile pepper (Capsicum annuum) is widely produced and consumed, but farmers face significant challenges associated with high temperature stress. Tolerance to high temperatures is a phenotype comprised of numerous component traits each of which contribute to the overall performance of the plant. Our aim was to identify the key mechanisms associated with heat stress response in the leaves and in the floral organs of chile pepper. One-month-old plants of heat-sensitive (AVPP1609-038) and -tolerant (AVPP1609-015) recombinant inbred line (RIL) of chile pepper were subjected to heat stress (38 and 28°C day and night temperatures) and control conditions (32 and 24°C day and night temperatures) in growth chambers with a 14-hour photoperiod. Leaf and floral bud samples were collected for RNA extraction at 11 and 18 days after treatment, respectively, with four biological replicates per tissue. Differentially expressed genes (DEGs) were identified by comparing tolerant and sensitive RILs across treatments and tissues. For the heat-tolerant AVPP1609-015 under heat stress, 1,118 DEGs were identified, with 649 specific to floral buds, 381 in leaves, and 88 shared between the two tissues. Biological processes such as RNA splicing and heat acclimation were predominantly upregulated in floral buds, while lipid catabolism was enhanced in leaves. Developmental processes were consistently suppressed in both tissues for the RILs under heat stress conditions. For the heat-tolerant AVPP1609-015 nuclease activity was strongly suppressed, likely to preserve nucleic acid integrity under heat stress. Hormonal regulation showed tissue specificity, with salicylic acid playing a pivotal role in leaves and ethylene in floral buds, potentially associated with flower abscission. Additionally, key transcription factors associated with heat tolerance were identified. While some mechanisms of heat tolerance were shared between tissues, distinct responses were observed as well, suggesting the need for different breeding approaches to enhance heat tolerance in vegetative and reproductive tissues of chile pepper. These findings provide valuable insights for developing heat-resilient chile pepper and a foundation for future research.