Identification of Brassica oleracea orthologs of the PEBP family and their expression patterns in curd development and flowering in cauliflower

Abstract

The PEBP family members are reported to play important roles in plant flowering and reproductive organ formation. However, this gene family has not been identified nor their functions have been analyzed in Brassica oleracea. In this study, 10 PEBP genes were identified in the B. oleracea genome. These genes were categorized as TFL1, FT and MFT subfamilies according to the phylogeny and gene structure analysis. All the 10 PEBP genes were randomly distributed on seven of the nine chromosomes in B. oleracea. The expression profiles of the 10 PEBP genes in different tissues of cauliflower were evaluated through quantitative Real-Time polymerase chain reaction (qRT-PCR), and we found that FT and TFL1 genes tend to be expressed in reproductive organs and at high levels in the meristem, whereas the MFT genes showed no or very low expression in all tested tissues. Notably, the five TFL1 genes might be sub-functionalized in cauliflower. Bol026421 and Bol032920 were specifically expressed in SAMbr, maintaining the indeterminate growth of shoot apical meristem, whereas the other three genes (Bol015337, Bol005471 and Bol010027) were highly expressed in curd stages. Highly expressed TFL1 group genes with low mRNA levels of the flowering-promoting genes (FT, TSF), might be one of the important reasons of curd formation in cauliflower. Generally, the results obtained in this study will help further studies on the roles of PEBP genes during curd development and flowering initiation, leading to crop improvement.