AUTHOR=Fudge Jared B. , Lee Robyn H. , Laurie Rebecca E. , Mysore Kirankumar S. , Wen Jiangqi , Weller James L. , Macknight Richard C. 

TITLE=Medicago truncatula SOC1 Genes Are Up-regulated by Environmental Cues That Promote Flowering

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00496

DOI=10.3389/fpls.2018.00496

ISSN=1664-462X

ABSTRACT=<p>Like <italic>Arabidopsis thaliana</italic>, the flowering of the legume <italic>Medicago truncatula</italic> is promoted by long day (LD) photoperiod and vernalization. However, there are differences in the molecular mechanisms involved, with orthologs of two key <italic>Arabidopsis thaliana</italic> regulators, <italic>FLOWERING LOCUS C</italic> (<italic>FLC</italic>) and <italic>CONSTANS</italic> (<italic>CO</italic>), being absent or not having a role in flowering time function in <italic>Medicago</italic>. In <italic>Arabidopsis</italic>, the MADS-box transcription factor gene, <italic>SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1</italic> (<italic>AtSOC1</italic>), plays a key role in integrating the photoperiodic and vernalization pathways. In this study, we set out to investigate whether the <italic>Medicago SOC1</italic> genes play a role in regulating flowering time. Three <italic>Medicago SOC1</italic> genes were identified and characterized (<italic>MtSOC1a–MtSOC1c</italic>). All three <italic>MtSOC1</italic> genes, when heterologously expressed, were able to promote earlier flowering of the late-flowering <italic>Arabidopsis soc1-2</italic> mutant. The three <italic>MtSOC1</italic> genes have different patterns of expression. However, consistent with a potential role in flowering time regulation, all three <italic>MtSOC1</italic> genes are expressed in the shoot apex and are up-regulated in the shoot apex of plants in response to LD photoperiods and vernalization. The up-regulation of <italic>MtSOC1</italic> genes was reduced in <italic>Medicago fta1-1</italic> mutants, indicating that they are downstream of <italic>MtFTa1.</italic> Insertion mutant alleles of <italic>Medicago soc1b</italic> do not flower late, suggestive of functional redundancy among <italic>Medicago SOC1</italic> genes in promoting flowering.</p>