Loss of Function of the - Gene Associates With Early Flowering Under Long-Day Conditions in Soybean.

Photoperiod response of flowering determines plant adaptation to different latitudes. Soybean, a short-day plant, has gained the ability to flower under long-day conditions during the growing season at higher latitudes, mainly through dysfunction of genes ( and ) and the floral repressor . In this study, we identified a novel molecular genetic basis of photoperiod insensitivity in Far-Eastern Russian soybean cultivars. By testcrossing these cultivars with a Canadian cultivar Harosoy near-isogenic line for a recessive allele, followed by association tests and fine mapping, we determined that the insensitivity was inherited as a single recessive gene located in an 842-kb interval in the pericentromeric region of chromosome 4, where (), a homoeolog of , is located. Sequencing analysis detected a single-nucleotide deletion in the coding sequence of the gene in insensitive cultivars, which generated a premature stop codon. Near-isogenic lines (NILs) for the loss-of-function allele (designated ) exhibited upregulated expression of soybean () orthologs, and , and flowered earlier than those for under long-day conditions in both the / and / genetic backgrounds. These NILs further lacked the inhibitory effect on flowering by far-red light-enriched long-day conditions, which is mediated by , but not that of red-light-enriched long-day conditions, which is mediated by . These findings suggest that retards flowering under long-day conditions by repressing the expression of and independently of . This loss-of-function allele can be used as a new resource in breeding of photoperiod-insensitive cultivars, and may improve our understanding of the function of the family genes in the photoperiod responses of flowering in soybean.