Genome-wide identification and analysis of anthocyanin synthesis-related R2R3-MYB genes in Fragaria pentaphylla.

BACKGROUND

MYB transcription factors regulate anthocyanin biosynthesis across numerous plant species. However, comprehensive genome-wide investigations regarding the R2R3-MYB gene family and its involvement in regulating anthocyanin biosynthesis in the red and white fruit color morphs of Fragaria pentaphylla remain scarce.

RESULTS

A total of 101 FpR2R3-MYB genes were identified from the F. pentaphylla genome and were divided into 34 subgroups based on phylogenetic analysis. Gene structure (exon/intron) and protein motifs were particularly conserved among the FpR2R3-MYB genes, especially members within the same subgroup. The FpR2R3-MYB genes were distributed over seven F. pentaphylla chromosomes. Analysis of gene duplication events revealed five pairs of tandem duplication genes and 16 pairs of segmental duplication genes, suggesting that segmental duplications are the major pattern for expansion of the FpR2R3-MYB gene family expansion in F. pentaphylla. Cis-regulatory elements of the FpR2R3-MYB promoters were involved in cellular development, phytohormones, environmental stress and photoresponse. Based on the analysis of the FpR2R3-MYB gene family and transcriptome sequencing (RNA-seq) data, FpMYB9 was identified as a key transcription factor involved in the regulation of anthocyanin synthesis in F. pentaphylla fruits. The expression of FpMYB9 increases significantly during the ripening stage of red fruits, as confirmed by reverse transcription quantitative real-time PCR. In addition, subcellular localization experiments further confirmed the nuclear presence of FpMYB9, supporting its role as a transcription factor involved in anthocyanin biosynthesis.

CONCLUSION

Our results showed that the FpR2R3-MYB genes are highly conserved and play important roles in the anthocyanin biosynthesis in F. pentaphylla fruits. Our results also provide a compelling basis for further understanding of the regulatory mechanism underlying the role of FpMYB9 in anthocyanin formation in F. pentaphylla fruits.