Overexpression of Arabidopsis thaliana blue-light inhibitor of cryptochromes 1 gene alters plant architecture in soybean

Arabidopsis thaliana blue-light inhibitor of cryptochromes 1 (AtBIC1) suppresses the dimerization of cryptochromes, which is necessary for cryptochrome function in plants. Additionally, AtBIC1 interacts with brassinazole-resistant 1 (BZR1) and phytochrome-interacting factor 4 (PIF4) transcription factors for integrating brassinosteroid (BR) and light signaling to promote plant growth. Thus, AtBIC1 overexpression is postulated to facilitate a desirable plant architecture for a high yield of crops. We first confirmed the phenotypes of transgenic Arabidopsis plants overexpressing AtBIC1, showing increases in leaf growth, plant height, and seed productivity. Next, we applied the AtBIC1 overexpression approach to soybean as a target crop. The transgenic soybean plants overexpressing AtBIC1 exhibited a significantly tall phenotype (i.e., an increased plant height) but with reduced root growth. In particular, the transgenic soybean plants displayed altered plant architecture, such as greatly elongated hypocotyls, during growth under both greenhouse and field conditions. Due to the phenotype of increased plant height, the total seed weights from the transgenic soybean plants decreased. These results suggest that the greater growth of above-ground parts might result in diminished growth of underground parts (i.e., roots), reducing the seed productivity of soybean. Collectively, these results suggest that AtBIC1 overexpression functions similarly in elongated growth to increase plant heights in both Arabidopsis and soybean, whereas it functions differently in root growth between the two plants.