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Peel color is one of the most important appearance qualities of eggplant. The main pigment in the peel of green-fruited eggplant is chlorophyll, while white-fruited eggplant is a mutant of chlorophyll biosynthesis. A dominant gene Gv controls chlorophyll biosynthesis in eggplant peel, but none of its genes have been mapped. In this study, the white-peel inbred line 19141, the green-peel inbred line 19143, and their F2 progeny with 3:1 segregation ratio of green-peel plants to white-peel plants, were used to map the Gv1 locus by whole genome re-sequencing combined with bulked segregant analysis (BSA). The Gv1 gene was mapped in a region spanning 7.66 Mb on chromosome 8, which was narrowed down to 173.2 kb interval by screening recombinant plants with InDel and SNP markers. Sixteen candidate genes were annotated in the above closely associated region. With the aid of RNA-Seq data, it was speculated that SmAPPR2-like is the candidate gene for Gv1. The results of cloning and sequencing of SmAPPR2-like showed that there might have been three types of mutation (large deletion, frameshift variant and premature stop codon) in white-peel accessions, and of these, the deletion mutation, such as that in inbred line 19141, was the most common. Based on the sequence difference of SmAPPR2-like, molecular markers were developed to distinguish the white and green-peel accessions in natural eggplant populations, and the other types of genetic variations of SmAPPR2-like leading to white-peel accessions were elucidated. The present study not only provided reliable markers for MAS (marker-assisted selection) breeding for eggplant peel color, but also paved the way for understanding the molecular mechanism of SmAPPR2-like on chlorophyll biosynthesis in eggplant fruit. [ABSTRACT FROM AUTHOR]

Fruit color is an important trait influencing the commercial value of eggplant fruits. Three dominant genes (D , P and Y) cooperatively control the anthocyanin coloration in eggplant fruits, but none has been mapped. In this study, two white-fruit accessions (19 141 and 19 147) and their F2 progeny, with 9:7 segregation ratio of anthocyanin pigmented versus non-pigmented fruits, were used for mapping the D and P genes. A high-density genetic map was constructed with 5270 SNPs spanning 1997.98 cM. Three QTLs were identified, including two genes on chromosome 8 and one on chromosome 10. Gene expression analyses suggested that the SmANS on chromosome 8 and SmMYB1 on chromosome 10 were the putative candidate genes for P and D , respectively. We further identified (1) a SNP leading to a premature stop codon within the conserved PLN03176 domain of SmANS in 19 141, (2) a G base InDel in the promoter region leading to an additional cis -regulatory element and (3) a 6-bp InDel within the R2-MYB DNA binding domain of SmMYB1 , in 19 147. Subsequently, these three variations were validated by PARMS technology as related to phenotypes in the F2 population. Moreover, silencing of SmANS or SmMYB1 in the purple red fruits of F1 (E3316) led to inhibition of anthocyanin biosynthesis in the peels. Conversely, overexpression of SmANS or SmMYB1 restored anthocyanin biosynthesis in the calli of 19 141 and 19 147 respectively. Our findings demonstrated the epistatic interactions underlying the white color of eggplant fruits, which can be potentially applied to breeding of eggplant fruit peel color. [ABSTRACT FROM AUTHOR]

The eggplant (Solanum melongena L.) is one of the most important Solanaceae crops, ranking third for total production and economic value in its genus. Herein, we report a high‐quality, chromosome‐scale eggplant reference genome sequence of 1155.8 Mb, with an N50 of 93.9 Mb, which was assembled by combining PacBio long reads and Hi‐C sequencing data. Repetitive sequences occupied 70.1% of the assembly length, and 35,018 high‐confidence protein‐coding genes were annotated based on multiple sources. Comparative analysis revealed 646 species‐specific families and 364 positive selection genes, conferring distinguishing traits on the eggplant. We performed genome‐wide comparative identification of disease resistance genes and discovered an expanded gene family of bacterial spot resistance in eggplant and pepper, but not in tomato and potato. The genes involved in chlorogenic acid synthesis were comprehensively characterized. Highly similar chromosomal distribution patterns of polyphenol oxidase genes were observed in the eggplant, tomato, and potato genomes. The eggplant reference genome sequence will not only facilitate evolutionary studies of the Solanaceae but also facilitate their breeding and improvement. [ABSTRACT FROM AUTHOR]

Wild relatives represent a source of variation for many traits of interest for eggplant (Solanum melongena) breeding, as well as for broadening its genetic base. However, interspecific hybridization with wild relatives has been barely used in eggplant breeding programs, and reproductive barriers have resulted in reduced seed numbers in interspecific combinations. The mechanism underlying this phenomenon remains unclear. We hybridized females of cultivated eggplant 177 (Solanum melongena) with males of wild relatives 53 and Y11 (Solanum aethiopicum). Self-crossed 177 was the control. The seed number per control fruit was significantly higher than that of the hybrids. Paraffin sections showed no significant difference between control and 177×53 and 177×Y11. Double fertilization began 4 days post-pollination. Sperm cells were fused with egg cells 6 days post-pollination. To understand the differences in molecular mechanisms underlying this process, transcriptomes of ovaries at 0, 4, and 6 days after self-crossing and hybridization were analyzed. We screened 22,311 differentially expressed genes (DEGs) between the control and hybrids 4 and 6 days post-pollination. A total of 497 DEGs were shared among all pollination combinations. These DEGs were enriched in plant hormone transduction, cell senescence, metabolism, and biosynthesis pathways. DEG clustering analysis indicated distinct expression patterns between the control and hybrids but not between the hybrids. The DEGs in hybrids involved secondary metabolic process, phenylpropanoid metabolic process, and carboxypeptidase activity, while those in the control involved xyloglucan metabolic process, auxin-activated signaling pathway, cell wall polysaccharide metabolic process, and xyloglucosyl transferase activity. Additionally, 1683 transcription factors, including members of the AP2-ERF, MYB, bHLH, and B3 families may play important roles in self-crossing and hybridization. Our results provide insights into the regulatory mechanisms underlying variations between ovaries of self-crossed and hybrid eggplants and a basis for future studies on crossbreeding Solanum and genetic mechanisms underlying double fertilization. [ABSTRACT FROM AUTHOR]

Heterostyly is a common floral polymorphism, but the proteomic basis of this trait is still largely unexplored. In this study, self- and cross-pollination of L-morph and S-morph flowers and comparison of embryo sac development in eggplant (Solanum melongena L.) suggested that lower fruit set from S-morph flowers results from stigma-pollen incompatibility. To explore the molecular mechanism underlying heterostyly development, we conducted isobaric tags for relative and absolute quantification (iTRAQ) proteomic analysis of eggplant pistils for L- and S-morph flowers. A total of 5,259 distinct proteins were identified during heterostyly development. Compared S-morph flowers with L-morph, we discovered 57 and 184 differentially expressed proteins (DEPs) during flower development and maturity, respectively. Quantitative real time polymerase chain reactions were used for nine genes to verify DEPs from the iTRAQ approach. During flower development, DEPs were mainly involved in morphogenesis, biosynthetic processes, and metabolic pathways. At flower maturity, DEPs primarily participated in biosynthetic processes, metabolic pathways, and the formation of ribosomes and proteasomes. Additionally, some proteins associated with senescence and programmed cell death were found to be upregulated in S-morph pistils, which may lead to the lower fruit set in S-morph flowers. Although the exact roles of these related proteins are not yet known, this was the first attempt to use an iTRAQ approach to analyze proteomes of heterostylous eggplant flowers, and these results will provide insights into biochemical events taking place during the development of heterostyly. [ABSTRACT FROM AUTHOR]