Gene Expression Patterns Regulating Peanut Reproductive Phenology

Peanut reproduction is foundational for crop yield, breeding, and evolution. However, gene regulation underlying peanut flowering pattern and timing has received limited attention. Cultivated peanut (Arachis hypogaea L.) shows two distinct flowering patterns between two subspecies, with ssp. hypogaea lacking flowers on the main stem and ssp. fastigiata having them. Understanding the gene regulatory networks that control peanut flowering will inform the genetic pathways impacting peanut reproduction, phenology, and yield. To this end, we measured whole-transcriptome gene expression of leaves and shoot tips (meristem) at six plant growth stages from Tifrunner, a peanut cultivar belonging to ssp. hypogaea, and GT-C20, a peanut germplasm belonging to ssp. fastigiata. Overall gene expression was distinct between the two genotypes in both tissue types. Flowering regulators including AhFT, AhSOC1, AhAGL42, and AhSPL3 were differentially expressed in both the main and lateral stem at the time of flowering initiation (T3-first bloom). This indicates that positive regulation of these flowering regulators drives the distinct pattern of flowering on the main stem in GT-C20. Meanwhile, the differential expression of two RING-finger E3 ubiquitin ligases was identified between the two genotypes, indicating that the PAF1-complex (PAF1C) may contribute to the lack of flowering on the main stem of Tifrunner. Gene co-expression network analysis indicates that gibberellic acid (GA) and jasmonic acid (JA) pathways are involved in reproductive regulation. These results provide insight into how flowering physiology is differentially controlled between the two peanut subspecies and provide a launching point for additional research in peanut floral development.