Target-Genes Reveal Species and Genotypic Specificity of Anthocyanin Pigmentation in Citrus and Related Genera

Abstract

Background: Anthocyanin pigmentation characterizes a number of tissues of Citrus and its relatives. The gain and loss of pigmentation is intriguing and is inherited variously among species. Methods: Citrus germplasm was used to investigate the anthocyanin pigmentation of tissues never before considered, including stamen, style and stigma, and of young leaves, petals, rind and flesh of 28 genotypes belonging to 14 species. Citrus genotypes encompassed citron, lemon, sweet orange, lime, and Citrus relatives included Microcitrus, Murraya, and Severinia. A relative qRT-PCR analysis was carried out on the structural and regulatory genes: phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3′-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), uridine diphosphate glucose flavonoid glucosyl-transferase (UFGT), glutathione S-transferase (GST), Ruby and Noemi. Image analysis and a genomic approach were employed to evaluate how the red pigmentation is inherited among tissues and species. Results: Pigmentation of young leaves and petals is specific to citron and its hybrids. Ruby controls the pigmentation of petals, but not of leaves. The red color of the rind and flesh is a trait that particularly characterizes a diversity of sweet oranges, citron hybrids and Citrus relatives. Color expression depends on external factors and also on developmental stage. The coloration of stamen and style is citron-specific, while a red stigma is exclusive to Moro orange and its hybrids. Conclusion: It is hypothesized that there is a relationship among Citrus species and genes controlling anthocyanin pigmentation.

Rootstock Effects on Anthocyanin Accumulation and Associated Biosynthetic Gene Expression and Enzyme Activity during Fruit Development and Ripening of Blood Oranges

“…There was a strong correlation between 4CL (Figure 7C) activity and anthocyanin concentration, and its dynamic change correlated with anthocyanin concentration change (Figure 10), suggesting that 4CL participates in anthocyanin synthesis. Repression of DFR in blonde oranges [26] and its up-regulation in the pulp of pigmented citrus fruits [39] show that DFR is a key anthocyanin biosynthesis gene. DFR reached the highest expression at 270 DAFB, but its expression was significantly (p < 0.05)) lower in Pt than in Cj and Cr groups at the ripening stage.…”

Molecular Insights into the Effects of Rootstocks on Maturation of Blood Oranges

“…A key gene for synthesis of anthocyanin is DFR because its transcription is generally not detected in blonde oranges [42] and it is highly up-regulated in the flesh of pigmented citrus fruits [43]. Both DFR and ANS were generally downregulated for CAR compared to for BIT or FUR and seemed to reach highest expression only at 276 DAFB, two months later than for BIT and one month later than for FUR (Figure 4).…”

Genomic insights into citrus domestication and its important agronomic traits

“…(2019b) 29 CgRuby1 , CgRuby2 , AbRuby2 Atalantia and pummelo A. thaliana Huang et al. (2018) 30 Ruby and Noemi (bHLH) Citrus – Catalano et al. (2020) 31 MYB3 Sweet orange Arabidopsis Huang et al.…”