Soybean is an important legume crop that displays the classic shade avoidance syndrome (SAS), including exaggerated stem elongation, which leads to lodging and yield reduction under density farming conditions. Here, we compared the effects of two shade signals, low red light to far-red light ratio (R:FR) and low blue light (LBL), on soybean status and revealed that LBL predominantly induces excessive stem elongation. We used CRISPR-Cas9-engineered Gmcry mutants to investigate the functions of seven cryptochromes (GmCRYs) in soybean and found that the four GmCRY1s overlap in mediating LBL-induced SAS. Lightactivated GmCRY1s increase the abundance of the bZIP transcription factors STF1 and STF2, which directly upregulate the expression of genes encoding GA2 oxidases to deactivate GA 1 and repress stem elongation. Notably, GmCRY1b overexpression lines displayed multiple agronomic advantages over the wild-type control under both dense planting and intercropping conditions. Our study demonstrates the integration of GmCRY1-mediated signals with the GA metabolic pathway in the regulation of LBL-induced SAS in soybean. It also provides a promising option for breeding lodging-resistant, high-yield soybean cultivars in the future.

Nitrogen fixation in legume roots Soybeans and other legumes form symbiotic relationships with nitrogen-fixing bacteria in root nodules, thus ensuring the plant a ready supply of the necessary nutrient. Wang et al . worked out the signaling pathways that integrate above-ground light with below-ground root nodulation. Two mobile regulators move from shoot to root in response to light and, together, they form a signaling module in the root that induces the expression of nodulation factors. Thus, when the shoot sees enough light to support photosynthetic productivity, the root gets the signal to ramp up nitrogen fixation. —PJH

Cryptochrome 1 (CRY1) is an important light receptor essential for de-etiolation of Arabidopsis seedlings. However, its function in regulating plant architecture remains unclear. Here, we show that mutation in CRY1 resulted in increased branching of Arabidopsis plants . To investigate the underlying mechanism, we analyzed the expression profiles of branching-related genes and found that the mRNA levels of Phytochrome Interaction Factor 4 ( PIF4 ) and PIF5 are significantly increased in the cry1 mutant. Genetic analysis showed that the pif4 or pif4pif5 mutant is epistatic to the cry1 mutant, and overexpression of PIF4 conferred increased branching. Moreover, we demonstrated that PIF4 proteins physically associate with the G-box motif within the PIF4 promoter to form a self-activated transcriptional feedback loop, while CRY1 represses this process in response to blue light. Taken together, this study suggests that the CRY1–PIF4 module regulates gene expression via forming a regulatory loop and shoot branching in response to ambient light conditions.