A 14 nucleotide deletion mutation in the coding region of the PpBBX24 gene is associated with the red skin of “Zaosu Red” pear (Pyrus pyrifolia White Pear Group): a deletion in the PpBBX24 gene is associated with the red skin of pear

Abstract

Red skin is an important quality trait for pear fruits and is determined by the concentration and composition of anthocyanins. The regulatory mechanism underlying anthocyanin accumulation is a popular topic in fruit research. Red mutants are ideal materials for studying the molecular mechanism of color diversity in pear. Although several red pear mutants have been cultivated and are in production, no exact locus containing the responsible genetic mutation has been identified. In this study, by combining the bulked segregant analysis with whole-genome sequencing, we identified a 14 nucleotide deletion mutation in the coding region of the PpBBX24 gene from the red pear mutant "Zaosu Red". We further verified that the deletion was present only in the red mutant of "Zaosu" and in its red offspring, which was different from that which occurred in other red pear fruits. This deletion results in a coding frame shift such that there is an early termination of the PpBBX24 gene and loss of key NLS and VP domains from PpBBX24. The lost domains may reduce or alter the normal function of PpBBX24. In addition, we found that the transcript levels of the PpMYB10 and PpHY5 genes in red samples were significantly higher than those in green samples, whereas the results for the normal-type PpBBX24 gene were the opposite. We ultimately revealed that the 14 nucleotide deletion mutation in the coding region of the PpBBX24 gene is associated with the red skin of the "Zaosu Red" pear. This finding of somatic mutational events will be helpful for breeding new red pear cultivars and for understanding the regulatory mechanisms involved in pear skin pigmentation.

Anthocyanin Accumulation and Related Gene Expression Profile in ‘Red Zaosu’ Pear and Its Green Mutant

“…However, it is hard to obtain a red peel color in oriental pear. Mutation selection is one of the most efficient approaches to obtain redskinned pear cultivars, like the 'Red Zaosu' pear, originated from a red mutant of 'Zaosu' [3]. The concentration and the composition of anthocyanin are the determinants of fruit red coloration, which is controlled by structural genes and regulatory genes in the anthocyanin biosynthetic pathway [24,25].…”

“…The degree of red coloration in the skin of pears is determined by the content and composition of anthocyanins. Cyanidin-3-galactoside is the major anthocyanin responsible for the red appearance [1][2][3]. Anthocyanins play important roles during plant growth and development and are involved in a wide range of biological processes, such as the attraction of pollinators and seed dispersers and the protection against biotic and abiotic stresses [4,5].…”

Bulk segregation analysis in the NGS era: a review of its teenage years

“…BSA combined with GWAS analysis of natural populations was used for colocalization to improve mapping resolution (Du et al., 2018; Jiang et al., 2019; Su et al., 2019). BSA and transcriptomics were combined to screen for differentially expressed genes within the mapped intervals (Baek et al., 2017; Hao et al., 2019; Kim et al., 2015; Ou et al., 2020; Wen et al., 2019). Combining BSA with multiomics is also a powerful strategy to achieve fine mapping and candidate gene screening.…”

Two B-Box Proteins, MaBBX20 and MaBBX51, Coordinate Light-Induced Anthocyanin Biosynthesis in Grape Hyacinth

“…Based on the number and type of domains carried, BBX proteins can be divided into five structural groups [ 24 ]. Two types of BBX regulators involved in the fine-tuning of light-regulated anthocyanin pigmentation, i.e., positive and negative BBX regulatory proteins, mainly belong to structural group IV or V [ 25 ]. In Arabidopsis , AtBBX21 positively regulates anthocyanin accumulation and inhibits the elongation of the seedling hypocotyl in response to light by binding to the promoters of chalcone isomerase and HY5 and directly activating their expression, both independently and together with HY5 [ 26 ].…”

“…AtBBX32 negatively modulates anthocyanin accumulation by interacting with AtBBX21 to suppress AtBBX21-HY5 activity [ 33 ]. Recent studies have demonstrated that BBX proteins are also involved in regulating anthocyanin accumulation during fruit skin colouration [ 20 , 25 , 34 , 35 , 36 ]. In apple plants, MdCOL11 [ 37 ], MdBBX20 [ 38 ], and MdBBX22 [ 39 ] are positive regulators of UV-B-induced anthocyanin biosynthesis, whereas MdCOL4 [ 36 ] and MdBBX37 [ 40 ] are negative regulators in response to UV-B/light radiation of fruit skin.…”