Kihwan Kim, Deokmoon Lee, Hyun Jo, Jong Tae Song, Jeong-Dong Lee
Plant architecture results from the integration of developmental regulatory networks and environmental signaling pathways. In soybean, the erect growth habit of cultivated soybean (Glycine max) contrasts markedly with the vine growth habit (VGH) of wild soybean (Glycine soja). However, the genetic and transcriptional mechanisms underlying this divergence in gibberellin-mediated stem elongation remain poorly understood. Therefore, this study aims to investigate the genetic, transcriptional, and hormonal basis underlying the differences in growth habit between Williams 82 (erect growth habit) and PI 366121 (VGH). PI 366121 exhibited accelerated stem elongation at the V3 growth stage, indicating a developmentally regulated onset of the VGH. Quantitative trait locus (QTL) mapping using a high-density bin-based linkage map identified a major QTL on chromosome 14, encompassing 20 candidate genes. At the V3 growth stage, Williams 82 exhibited transcriptional expression patterns associated with enhanced photodamage repair and ROS detoxification, whereas PI 366121 exhibited coordinated activation of photoprotective, circadian, and gibberellin-responsive regulatory networks. Weighted gene co-expression network analysis was used to identify an ELIP-mediated regulatory module associated with the VGH. Furthermore, the co-expression of ELIP and GASA22 genes supports a functional relationship between chloroplast redox homeostasis and gibberellin-mediated stem elongation. We propose that ELIP-mediated photoprotection maintains photosystem II redox homeostasis, suppresses CBF-dependent GA2ox gene expression, and sustains bioactive gibberellin accumulation, thereby promoting GASA22 activation and stem elongation. This ELIP-GASA22 regulatory module provides a molecular framework connecting chloroplast redox status with gibberellin signaling and morphological plasticity in wild soybean.