The Expression of IbMYB1 Is Essential to Maintain the Purple Color of Leaf and Storage Root in Sweet Potato [Ipomoea batatas (L.) Lam]

Abstract

IbMYB1 was one of the major anthocyanin biosynthesis regulatory genes that has been identified and utilized in purple-fleshed sweet potato breeding. At least three members of this gene, namely, IbMYB1-1, -2a, and -2b, have been reported. We found that IbMYB1-2a and -2b are not necessary for anthocyanin accumulation in a variety of cultivated species (hexaploid) with purple shoots or purplish rings/spots of flesh. Transcriptomic and quantitative reverse transcription PCR (RT-qPCR) analyses revealed that persistent and vigorous expression of IbMYB1 is essential to maintain the purple color of leaves and storage roots in this type of cultivated species, which did not contain IbMYB1-2 gene members. Compared with IbbHLH2, IbMYB1 is an early response gene of anthocyanin biosynthesis in sweet potato. It cannot exclude the possibility that other MYBs participate in this gene regulation networks. Twenty-two MYB-like genes were identified from 156 MYBs to be highly positively or negatively correlated with the anthocyanin content in leaves or flesh. Even so, the IbMYB1 was most coordinately expressed with anthocyanin biosynthesis genes. Differences in flanking and coding sequences confirm that IbMYB2s, the highest similarity genes of IbMYB1, are not the members of IbMYB1. This phenomenon indicates that there may be more members of IbMYB1 in sweet potato, and the genetic complementation of these members is involved in the regulation of anthocyanin biosynthesis. The 3′ flanking sequence of IbMYB1-1 is homologous to the retrotransposon sequence of TNT1-94. Transposon movement is involved in the formation of multiple members of IbMYB1. This study provides critical insights into the expression patterns of IbMYB1, which are involved in the regulation of anthocyanin biosynthesis in the leaf and storage root. Notably, our study also emphasized the presence of a multiple member of IbMYB1 for genetic improvement.

Combining Metabolomics and Transcriptomics to Reveal the Mechanism of Coloration in Purple and Cream Mutant of Sweet Potato (Ipomoea batatas L.)

“…In view of the IbMYB1 gene has been reported as a mutate location in some purple sweet potato and responsible for anthocyanin accumulation in the storage roots (Tanaka et al, 2012 ; Zhang D. et al, 2021 ), we amplified the gene IbMYB1-2a/b with the specific makers. The result showed that IbMYB1-2a/b was only amplified in Xuzi201 and lost in M1001 ( Figure 7 ).…”

“…IbMYB1-2a/2b fragments were amplified in the 20 μl mixture containing 2 × Taq PCR MasterMix II (TIANGEN BIOTECH, Beijing, China), 5 μM foreword primer, 5 μM reverse primer, and 50 ng cDNA under the following program: 94°C for 3 min; 35 cycles of 94°C for 15 s, 54°C for 30 s, and 72°C for 45 s; and 72°C for 5 min. The primers were used according to the study by Tanaka et al ( 2012 ) and Zhang D. et al ( 2021 ) and are shown in Supplementary Table S1 .…”

“…IbMYB1 belongs to the R2R3-MYB that are involved in anthocyanin biosynthesis and was isolated and specifically expressed in the PFSP roots. Expression of IbMYB1 alone was sufficient for the induction of all structural anthocyanin genes and anthocyanin accumulation in the flesh of tuberous roots (Mano et al, 2007 ; Park et al, 2015 ; Zhang D. et al, 2021 ). IbMYB1 -2a/b was identified as a mutation site in the white flesh mutation of purple sweet potato, which is responsible for anthocyanin accumulation in the storage roots (Tanaka et al, 2012 ), but the expression of IbMYB1 in all varieties is not necessary (Kim et al, 2010 ; Li et al, 2019 ; Zhang et al, 2020 ).…”

Anthocyanin-Rich Vegetables for Human Consumption—Focus on Potato, Sweetpotato and Tomato

“…It is an early response gene of anthocyanin biosynthesis. IbMYB2s , the highest similarity genes of IbMYB1 , are not the members of IbMYB1 , thereby suggesting there may be more members of IbMYB1 involved in the regulation of anthocyanin biosynthesis [ 85 ]. A genome wide association study (GWAS)-eQTL analysis revealed IbMYB1-2 as a master regulator and a major gene responsible for the activation of anthocyanin biosynthesis in the storage roots of sweet potato [ 86 ].…”

Comparative transcriptome analysis of purple-fleshed sweet potato and its yellow-fleshed mutant provides insight into the transcription factors involved in anthocyanin biosynthesis in tuberous root

“…The R2R3-MYB factors in the complex are the most crucial for the spatial and temporal localization of anthocyanins ( Davies et al, 2012 ). IbMYB1 controls anthocyanin biosynthesis in tuberous roots ( Mano et al, 2007 ), and its expression is essential for the purple color of leaf and storage root in sweet potato ( Zhang et al, 2021a ). Based on the sequences of coding regions, IbMYB1 amplified products from a purple-fleshed sweet potato, Ayamurasaki, were classified into two genotypes, IbMYB1-1 -type and IbMYB1-2 -type, whereas IbMYB1 amplified product from its spontaneous mutant, AYM96, belonged to IbMYB1-1 -type ( Tanaka et al, 2012 ).…”