ABSTRACT
Photoperiod strictly controlled vegetative and reproductive growth stages in soybean. A soybean GmRAV transcription factor containing both AP2 and B3 domains was shown to be a key component of this process. We identified six polymorphisms in GmRAV promoter that showed significant association with flowering time and maturity of soybean in one or multiple environments. Soybean varieties with minor polymorphism exhibited longer growth period contributing to soybean adaptation to lower latitudes. The cis-acting element GT1CONSENSUS motif of GmRAV promoter controlled the growth period and shortened R5-R7 by reducing the expression level of GmRAV in soybean. Three GmRAV-overexpressing (GmRAV-ox) transgenic lines displayed later flowering time and maturity, shorter height and fewer numbers of leaves compared with control plants, and transgenic inhibition of GmRAV (GmRAV-i) soybean displayed earlier flowering time and maturity, and increased plant heights. 163 GmRAV-target genes were determined to be putatively directly bound and transcriptionally regulated by GmRAV by combining the results from the DAP-seq and RNA-seq analyses. Two GmRAV binding motifs [C(A/G/T)A(C)ACAA(G/T)A(C/T)A(G/T)] and [C(T/A)A(C/T) C(T/G)CTG] were identified. GmRAV acting downstream of E3E4 delayed soybean growth period by repressing GmFT5a transcriptional activity to guaranteed both vegetative and reproductive phase long enough to allow necessary energy reserved to be accumulated.
