Functional Characterization of the Gene Reveals Its Dual Role in Regulating the Flowering Time and Plant Height in L.

Alfalfa (), a perennial legume forage, is known for its high yield and good quality. As a long-day plant, it is sensitive to changes in the day length, which affects the flowering time and plant growth, and limits alfalfa yield. Photoperiod-mediated delayed flowering in alfalfa helps to extend the vegetative growth period and increase the yield. We isolated a blue-light phytohormone gene from the alfalfa genome that is an ortholog of soybean and named it . Gene expression analyses showed that responds to blue light and the circadian clock in alfalfa. We found that regulates the flowering time through the plant circadian clock pathway by inhibiting the transcription of and , thus suppressing () transcription. In addition, transgenic lines exhibited higher plant height and accumulated more biomass in comparison to wild-type plants. However, the increased fiber (NDF and ADF) and lignin content also led to a reduction in the digestibility of the forage. The key genes related to GA biosynthesis, , increased in the transgenic lines, while decreased for the inactive GA transformation. These findings offer novel insights on the function of in the regulation of the flowering time and plant height in cultivated . These insights into 's roles in alfalfa offer potential strategies for molecular breeding aimed at optimizing flowering time and biomass yield.