Epigenetic regulation of <Emphasis Type="Italic">MdMYB1</Emphasis> is associated with paper bagging-induced red pigmentation of apples

Main conclusion

Paper-bagging treatment can transform non-transcribed MdMYB1 - 2 and MdMYB1 - 3 alleles into transcribed alleles through epigenetic regulations, resulting in the red pigmentation of a normally non-red apple cultivar ‘Mutsu.’ Anthocyanin biosynthesis in apples is regulated by MdMYB1/A/10, an R2R3-Type MYB gene. ‘Mutsu,’ a triploid apple cultivar harboring non-transcribed MdMYB1-2 and MdMYB1-3 alleles, retains green skin color under field conditions. However, it can show red/pink pigmentation under natural or artificial ultraviolet-B (UV-B) light exposure after paper-bagging and bag removal treatment. In the present study, we found that in ‘Mutsu,’ paper bagging-induced red pigmentation was due to the activation of non-transcribed MdMYB1-2/-3 alleles, which triggered the expression of downstream anthocyanin biosynthesis genes in a UV-B-dependent manner. By monitoring the epigenetic changes during UV-B-induced pigmentation, no significant differences in DNA methylation and histone modifications in the 5′ upstream region of MdMYB1-2/-3 were recorded between the UV-B-treated fruit skin (red) and the fruit skin treated only by white light (green). In contrast, bag treatment lowered the DNA methylation in this region of MdMYB1-2/-3 alleles. Similarly, higher levels of histone H3 acetylation and trimethylation of H3 tail at lysine 4, and lower level of trimethylation of H3 tail at lysine 27 were observed in the 5′ upstream region of MdMYB1-2/-3 in the skin of the fruit immediately after bag removal. These results suggest that bagging treatment can induce epigenetic changes, facilitating the binding of trans factor(s) to MdMYB1-2/-3 alleles, resulting in the activation of these MYBs after bag removal.

     

Heterologous expression of oxytetracycline biosynthetic gene cluster in Streptomyces venezuelae WVR2006 to improve production level and to alter fermentation process

Applied Microbiology and Biotechnology - Heterologous expression is an important strategy to activate biosynthetic gene clusters of secondary metabolites. Here, it is employed to activate and...     

Effect of dietary L‐malic acid supplementation on growth,feed utilization and digestive function of juvenile GIFT tilapia Oreochromis niloticus (Linnaeus, 1758)

Two feeding trials (FTs) were conducted in 2013 and 2014, respectively, to determine the optimal L‐malic acid (LMA) level for juvenile GIFT (Genetically Improved Farmed Tilapia) Oreochromis niloticus. Except for the LMA level, the FT1 and FT2 had a similar diet formulation. In FT1, LMA was included at 0 (basal diet), 1, 4, 8, 16 and 32 g kg^?1, respectively. After 20 weeks, daily weight gain and feed conversion ratio were improved but not differentiated with 1–8 g kg^?1 LMA. Further increasing the LMA supply initially decreased the feed intake (16 g kg^?1), and then decreased both feed intake and feed utilization (32 g kg^?1), thus impairing the fish growth. FT2 was subsequently conducted with a smaller LMA range (0, 0.5, 1, 2, 4 and 8 g kg^?1, respectively) but was unfortunately terminated at the end of 8 weeks because 20% of the fish were badly injured during weighing. Unexpectedly, growth and feed utilization were still improved but not differentiated with 0.5–8 g kg^?1 LMA. In FT2, beneficial effects of LMA inclusion on the digestive function (pepsin, foregut amylase and foregut lipase), the activities of serum lysozyme and hepatic superoxide dismutase, and liver lipid peroxidation (malondialdehyde concentration) were found. Taking the results of FT1 and FT2 together, it could be concluded that dietary LMA supplementation at low concentrations (0.5–8 g kg^?1) could improve growth and feed utilization, but excess LMA (≥16 g kg^?1) might compromise feed intake and/or feed utilization, thus impairing fish growth. To reduce feed costs in commercial practice, 0.5 g kg^?1 LMA is recommended in the feed of juvenile GIFT tilapia based on the results of this study.