Under high temperature stress, a large number of proteins in plant cells will be denatured and inactivated. Meanwhile Hsfs and Hsps will be quickly induced to remove denatured proteins, so as to avoid programmed cell death, thus enhancing the thermotolerance of plants. Here, a comprehensive identification and analysis of the Hsf and Hsp gene families in eggplant under heat stress was performed. A total of 24 Hsf-like genes and 117 Hsp-like genes were identified from the eggplant genome using the interolog from Arabidopsis. The gene structure and motif composition of Hsf and Hsp genes were relatively conserved in each subfamily in eggplant. RNA-seq data and qRT-PCR analysis showed that the expressions of most eggplant Hsf and Hsp genes were increased upon exposure to heat stress, especially in thermotolerant line. The comprehensive analysis indicated that different sets of SmHsps genes were involved downstream of particular SmHsfs genes. These results provided a basis for revealing the roles of SmHsps and SmHsp for thermotolerance in eggplant, which may potentially be useful for understanding the thermotolerance mechanism involving SmHsps and SmHsp in eggplant.

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 (19141 and 19147) 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 5,270 SNPs spanning 1,997.98 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 19141, (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 19147. 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 19141 and 19147 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.

Resistant crop cultivars can recruit beneficial rhizobacteria to resist disease. However, whether this recruitment is regulated by quantitative trait loci (QTL) is unclear. The role of QTL in recruiting specific bacteria against bacterial wilt (BW) is an important question of practical significance to disease management. Here, to identify QTL controlling BW resistance, Super-BSA was performed in F₂ plants derived from resistant eggplant cultivar R06112 × susceptible cultivar S55193. The QTL was narrowed down through BC₁F₁-BC₃F₁ individuals by wilting symptoms and KASP markers. Rhizosphere bacterial composition of R06112, S55193, and resistant individuals EB158 (with the QTL) and susceptible individuals EB327 (without QTL) from BC₂F₁ generation were assessed by Illumina sequencing-based analysis, and the activation of plant immunity by the bacterial isolates was analyzed. Evidence showed that BW-resistant is controlled by one QTL located at the 270 kb region on chromosome 10, namely EBWR10, and nsLTPs as candidate genes confirmed by RNA-Seq. EBWR10 has a significant effect on rhizobacteria composition and significantly recruits Bacillus. pp. A SynCom of three isolated Bacillus. pp trains significantly reduced the disease incidence, changed activities of CAT, PPO, and PAL and concentration of NO, H₂O₂, and O₂⁻, activated SA and JA signaling-dependent ISR, and displayed immune activation against Ralstonia solanacearum in eggplant. Our findings demonstrate for the first time that the QTL can recruit beneficial rhizobacteria, which jointly promote the suppression of BW. This method charts a path to develop the QTL in resistant cultivar-driven probiotics to ameliorate plant diseases.

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.

NBS-LRR genes constitute one of the largest resistance gene families in plants, which play key roles in resistance to pathogens. Although the identification and characterization of the NBS-LRR gene family has been extensively reported in various species, a comprehensive analysis in eggplant has not been previously documented. In this study, a total of 269 SmNBS genes were identified in the eggplant genome. Based on domain classification and phylogenetic analysis, SmNBSs were divided into three subgroups 231 CNLs (CC-NBS-LRR), 36 TNLs (TIR-NBS-LRR), and 2 RNLs (RPW8-NBS-LRR). Chromosomal mapping analysis revealed an uneven distribution of SmNBSs in clusters across chromosomes, with a predominant presence on chromosomes 10, 11, and 12. Structural analysis identified eight conserved motifs previously reported in SmNBSs, exhibiting high conservation in both amino acid sequences and their order. Evolutionary analysis demonstrated that tandem duplication events mainly contributed to the expansion of SmNBS. Subsequently, qRT-PCR analysis demonstrated that nine SmNBSs exhibited differential expression patterns in response to R. solanacearum stress, with EGP05874.1 potentially involved in the resistance response. In conclusion, this study provides a comprehensive insight into SmNBSs, which will enhance the research on eggplant disease resistance and facilitate the breeding of new disease-resistant varieties.

The SPL (SQUAMOSA promoter-binding protein-like) transcription factor gene family plays a crucial role in the growth of plants, including fruit development. Although the SPL gene family has been widely studied in many plants, it remains unexplored in eggplant, an important Solanaceae vegetable crop. In this study, we performed a genome-wide analysis and identified 11 SmSPL genes with 10 motifs in the eggplant genome, which were assigned to five groups based on the amino acid sequences and the gene structure of the SBP domain. In addition, the expression patterns of 11 SmSPL genes were analyzed in different tissue types and at four different fruit development stages in eggplant. The results showed that all SmSPL genes were expressed differently in various tissues, suggesting that they may play different roles in the regulation of the development of different organs. Specifically, the expression level of SmSPL_5 was increased at the fruit expansion stage and showed the highest expression levels at 16 and 24 days after pollination, suggesting that it may be involved in regulating fruit development at both the fruit expansion and commercial fruit stages. Overall, this study provides an important basis for further exploring the function of the SmSPL gene family in eggplant.