Gene and Its Promoter Cloning, and Functional Validation of JmSOC1 Revealed Its Role in Promoting Early Flowering and the Interaction with the JmSVP Protein

<i>Juglans mandshurica</i>, a notable woody oil tree species, possesses both fruit and timber value. However, the complete heterodichogamous flowering mechanism in this species remains elusive. <i>SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1)</i> is a crucial regulator of flower bud development in <i>Arabidopsis thaliana</i>. In this study, we cloned the coding DNA sequence (CDS) of the <i>JmSOC1</i> gene, revealing a 705 base pair (bp) sequence that encodes a protein of 234 amino acids. The JmSOC1 protein contains a highly conserved MADS-box domain, indicating its role as a transcription factor, and is predominantly localized in the nucleus. The <i>JmSOC1</i> gene expressed the highest in flower buds. The peak expression level of <i>JmSOC1</i> during the physiological differentiation phase occurred earlier in male flower buds of protandry (MPD) on April 10th compared to female flower buds of protandry (FPD) on April 14th; similarly, the peak expression in female flower buds of protogyny (FPG) on April 2nd preceded that in male flower buds of protogyny (MPG) on April 14th. This may be the primary reason for the earlier differentiation of the male flowers in protandry individuals and the female flowers in protogyny individuals. Overexpression of <i>JmSOC1</i> in wild-type <i>A</i>. <i>thaliana</i> resulted in earlier flowering, accompanied by an upregulation of key flowering-related genes such as <i>LEAFY</i> (<i>LFY</i>), <i>APETALA1</i> (<i>AP1</i>), and <i>FLOWERING LOCUS T</i> (<i>FT</i>). To further explore the function of <i>JmSOC1</i>, a 782 bp promoter sequence of <i>JmSOC1</i> gene was cloned, which has been verified to have promoter activity by GUS staining. Furthermore, the interaction between the <i>JmSOC1</i> gene promoter and its upstream regulatory protein JmSVP was verified using a yeast one-hybrid. These results offer valuable insights into the molecular mechanisms underpinning the promotion of early flowering in <i>J. mandshurica</i> and hold promise for laying a theoretical foundation for the flowering regulation network of this species.