Prebiotic effect of galacto-N-biose on the intestinal lactic acid bacteria as enhancer of acetate production and hypothetical colonization.

Galacto-N-biose (GNB) is an important core structure of glycan of mucin glycoproteins in the gastrointestinal (GI) mucosa. Because certain beneficial bacteria inhabiting the GI tract, such as bifidobacteria and lactic acid bacteria, harbor highly specialized GNB metabolic capabilities, GNB is considered a promising prebiotic for nourishing and manipulating beneficial bacteria in the GI tract. However, the precise interactions between GNB and beneficial bacteria and their accompanying health-promoting effects remain elusive. First, we evaluated the proliferative tendency of beneficial bacteria and their production of beneficial metabolites using gut bacterial strains. By comparing the use of GNB, glucose, and inulin as carbon sources, we found that GNB enhanced acetate production in Lacticaseibacillus casei, Lacticaseibacillus rhamnosus, Lactobacillus gasseri, and Lactobacillus johnsonii. The ability of GNB to promote acetate production was also confirmed by RNA-seq analysis, which indicated the upregulation of gene clusters that catalyze the deacetylation of N-acetylgalactosamine-6P and biosynthesize acetyl-CoA from pyruvate, both of which result in acetate production. To explore the in vivo effect of GNB in promoting acetate production, antibiotic-treated BALB/cA mice were administered with GNB with L. rhamnosus, resulting in a fecal acetate content that was 2.7-fold higher than that in mice administered with only L. rhamnosus. Moreover, 2 days after the last administration, a 3.7-fold higher amount of L. rhamnosus was detected in feces administered with GNB with L. rhamnosus than in feces administered with only L. rhamnosus. These findings strongly suggest the prebiotic potential of GNB in enhancing L. rhamnosus colonization and converting L. rhamnosus into higher acetate producers in the GI tract. IMPORTANCE: Specific members of lactic acid bacteria, which are commonly used as probiotics, possess therapeutic properties that are vital for human health enhancement by producing immunomodulatory metabolites such as exopolysaccharides, short-chain fatty acids, and bacteriocins. The long residence time of probiotic lactic acid bacteria in the GI tract prolongs their beneficial health effects. Moreover, the colonization property is also desirable for the application of probiotics in mucosal vaccination to provoke a local immune response. In this study, we found that GNB could enhance the beneficial properties of intestinal lactic acid bacteria that inhabit the human GI tract, stimulating acetate production and promoting intestinal colonization. Our findings provide a rationale for the addition of GNB to lactic acid bacteria-based functional foods. This has also led to the development of therapeutics supported by more rational prebiotic and probiotic selection, leading to an improved healthy lifestyle for humans.

Non-vernalization requirement for flowering in Brassica rapa conferred by a dominant allele of FLOWERING LOCUS T.

KEY MESSAGE: We identified and characterized a dominant FT allele for flowering without vernalization in Brassica rapa, while demonstrating its potential for deployment in breeding to accelerate flowering in various Brassicaceae crops. Controlling the timing of flowering is key to improving yield and quality of several agricultural crops including the Brassicas. Many Brassicaceae crops possess a conserved flowering mechanism in which FLOWERING LOCUS C (FLC) represses the transcription of flowering activators such as FLOWERING LOCUS T (FT) during vernalization. Here, we employed genetic analysis based on next-generation sequencing to identify a dominant FT allele, BraA.FT.2-C, for flowering in the absence of vernalization in the Brassica rapa cultivar 'CHOY SUM EX CHINA 3'. BraA.FT.2-C harbors two large insertions upstream of its coding region and is expressed without vernalization, despite FLC expression. We show that BraA.FT.2-C offers an opportunity to introduce flowering without vernalization requirement into winter-type brassica crops, including B. napus, which have many functional FLC paralogs. Furthermore, we demonstrated the feasibility of using B. rapa harboring BraA.FT.2-C as rootstock for grafting to induce flowering in radish (Raphanus sativus), which requires vernalization for flowering. We believe that the ability of BraA.FT.2-C to overcome repression by FLC can have significant applications in brassica crops breeding to increase yields by accelerating or delaying flowering.