AUTHOR=Akter Ayasha , Itabashi Etsuko , Kakizaki Tomohiro , Okazaki Keiichi , Dennis Elizabeth S. , Fujimoto Ryo 

TITLE=Genome Triplication Leads to Transcriptional Divergence of FLOWERING LOCUS C Genes During Vernalization in the Genus Brassica

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.619417

DOI=10.3389/fpls.2020.619417

ISSN=1664-462X

ABSTRACT=<p>The genus <italic>Brassica</italic> includes oil crops, vegetables, condiments, fodder crops, and ornamental plants. <italic>Brassica</italic> species underwent a whole genome triplication event after speciation between ancestral species of <italic>Brassica</italic> and closely related genera including <italic>Arabidopsis thaliana</italic>. Diploid species such as <italic>Brassica rapa</italic> and <italic>Brassica oleracea</italic> have three copies of genes orthologous to each <italic>A. thaliana</italic> gene, although deletion in one or two of the three homologs has occurred in some genes. The floral transition is one of the crucial events in a plant’s life history, and time of flowering is an important agricultural trait. There is a variation in flowering time within species of the genus <italic>Brassica</italic>, and this variation is largely dependent on a difference in vernalization requirements. In <italic>Brassica</italic>, like in <italic>A. thaliana</italic>, the key gene of vernalization is <italic>FLOWERING LOCUS C</italic> (<italic>FLC</italic>). In <italic>Brassica</italic> species, the vernalization response including the repression of <italic>FLC</italic> expression by cold treatment and the enrichment of the repressive histone modification tri-methylated histone H3 lysine 27 (H3K27me3) at the <italic>FLC</italic> locus is similar to <italic>A. thaliana</italic>. <italic>B. rapa</italic> and <italic>B. oleracea</italic> each have four paralogs of <italic>FLC</italic>, and the allotetraploid species, <italic>Brassica napus</italic>, has nine paralogs. The increased number of paralogs makes the role of <italic>FLC</italic> in vernalization more complicated; in a single plant, paralogs vary in the expression level of <italic>FLC</italic> before and after vernalization. There is also variation in <italic>FLC</italic> expression levels between accessions. In this review, we focus on the regulatory circuits of the vernalization response of <italic>FLC</italic> expression in the genus <italic>Brassica</italic>.</p>