A minimal two-amino-acid deletion in SmMYB1 converts an activator into a dominant repressor, reshaping global eggplant anthocyanin pigmentation during domestication.
Jul 2026· Plant Communications· pp.
101988
· 0 citations
Medicine
TL;DR
This study uncovers a rare case in which a deletion of just two amino acids is sufficient to generate a potent dominant-negative regulator, designated SmMYB1alf-D, which enables reliable prediction of fruit color and provides a breeding strategy to precisely manipulate anthocyanin metabolism.
Abstract
Eggplant fruits exhibit remarkable natural variation in both the intensity and spatial distribution of anthocyanin pigmentation, yet the genetic bases underlying the dominant anthocyaninless fruit (ALF) phenotype in many white- and green-fruited accessions remain unclear. Using bulked segregant analysis, we identified a 6-bp deletion within the coding sequence of SmMYB1 as the causal mutation underlying the ALF trait. Functional characterization revealed that this deletion converts the core fruit coloration regulator SmMYB1 from a transcriptional activator into a dominant-negative repressor, designated SmMYB1alf-D. While SmMYB1alf-D loses its ability to bind target gene promoters, it retains the complete protein-interaction network of the wild-type SmMYB1, thereby sequestering essential partners and effectively suppressing the expression of anthocyanin biosynthetic genes. This strong suppression of anthocyanin structural genes by SmMYB1alf-D enables reliable prediction of fruit color and provides a breeding strategy to precisely manipulate anthocyanin metabolism. Notably, unlike previously reported dominant-negative mutants that often involve large protein truncations, this study uncovers a rare case in which a deletion of just two amino acids is sufficient to generate a potent dominant-negative regulator. Phylogenetic, geographic, haplotypic and historical evidence strongly suggests that alf-D originated as a spontaneous mutation from a purple eggplant cultivar in North China approximately 1200 years ago. Moreover, its emergence and subsequent introgression represent a major mechanism underlying the origin of green/white-fruited eggplant varieties globally. Collectively, these findings highlight how a single, minimally altered natural allele originated, spread, and reshaped eggplant fruit pigmentation and offer a potential tool for precise phenotype engineering in molecular breeding.
Anthocyanins contribute to pigmentation, nutritional quality, and stress responses in plants. Although red spines are a characteristic trait of wild lettuce (Lactuca serriola), the genetic basis underlying spine pigmentation remains unclear. Here, we identified LsMYB3, a gene controlling spine color variation in wild lettuce. LsMYB3 encodes an R2R3-MYB transcription factor lacking a canonical repression motif but functioning as a negative regulator of anthocyanin biosynthesis. CRISPR/Cas9-mediated knockout of LsMYB3 enhanced anthocyanin accumulation, whereas overexpression suppressed pigmentation and converted red spines to green. Sequence analysis revealed that the natural Lsmyb3 allele carries a conserved Cys-to-Ser substitution within the R2 domain and a 1-bp deletion causing premature protein truncation, indicating loss of function. Yeast one-hybrid and dual-luciferase assays demonstrated that LsMYB3 directly represses LsDFR, a key anthocyanin biosynthetic gene. Notably, the effects of LsMYB3 disruption were tissue-specific and varied among genetic backgrounds, resulting in increased anthocyanin accumulation in wild lettuce spines and cultivated lettuce leaves. In addition, LsMYB3 physically interacted with the bHLH regulator RLL1, suggesting its involvement in the lettuce MBW regulatory network. Together, our findings identify LsMYB3 as a key negative regulator of anthocyanin biosynthesis and provide new insights into the evolution and diversification of pigmentation traits in lettuce.
Peinan Sun, Jing Ma, Xinyu Lang et al.· Plant Science· 0 citations
A multiplex CRISPR/Cas12a system is established in eggplant accession MEL3, representing, to the authors' knowledge, the first application of this nuclease for genome editing in eggplant and demonstrating the potential of Cas12a for functional genomics, allele engineering, and precision breeding in eggplant.
Marina Martínez-López, Andrea Solana, Andrea Arrones et al.· bioRxiv· 0 citations
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