Eggplant is a vegetable crop with high economic value that is cultivated worldwide. The dwarf mutant is an important germplasm material that has been extensively used in crop breeding. However, no eggplant dwarf mutants have been reported, and little is known regarding the genes responsible for dwarfism in eggplant. In this study, we isolated an eggplant dwarf mutant (dwf) from an ethyl methyl sulfonate (EMS)-induced mutant library. Genetic analysis revealed that dwf was caused by a single recessive gene. A candidate gene SmCPR1, encoding cytochrome P450 reductases (CPR1), was identified by bulked segregant analysis (BSA). Mutation from G to A at 8216 bp of SmCPR1 resulted in mutation of the amino acid from valine to isoleucine. The results of KASP and Sanger sequencing further support the conclusion that SmCPR1 is a candidate gene responsible for the dwarfism of dwf. Moreover, the activity of SmCPR1 was significantly increased in dwf, which might be a response to dwarfism in dwf.

Dwarfism is a desirable trait in eggplant breeding, as it confers higher lodging resistance and allows simplified management and harvest. However, a few dwarf mutants have been reported, and the molecular mechanism underlying dwarfism in eggplant is completely unknown. Here, we report a dwarf mutant (dwf) isolated from an ethyl methyl sulfonate (EMS)-induced mutant library. The hypocotyl length, plant height, and length of internode cells of dwf were significantly decreased compared to those of the wild-type parent ‘14-345’ (WT). Differential gene expression analysis revealed that GA-related genes, including GA2ox and DELLA, were up-regulated whereas the gibberellin (GA₃) content decreased in dwf. Moreover, exogenous GA₃ treatment significantly increased the relative growth rate of dwf compared to WT, further indicating the important roles of GA in regulating the dwarf phenotype of dwf. Collectively, our findings shed light on GA-mediated dwarfism in dwf plants and offer a good germplasm that could be used for eggplant dwarfism breeding in the future.

Leaf size is a crucial trait in eggplant breeding, as it influences photosynthesis, plant biomass and management. However, little is known about the molecular mechanism regulating leaf size in eggplant. This study reports a small leaf mutant (slf) generated with the mutagen ethyl methane sulfonate (EMS). The slf mutant showed restricted cell proliferation and an increased content of auxin. Transcriptome analysis revealed that several genes involved in auxin signaling are upregulated in slf. Exogenous application of auxinole, an auxin antagonist of TIR1/AFB receptors, repressed the expression of these genes and restored leaf growth of slf, suggesting that the small leaf size of slf is likely associated with auxin signaling. This study provides essential clues to unveil the molecular mechanism of leaf size regulation in eggplant.

TIR1/AFB proteins are a class of auxin receptors with key roles in plant development and biotic and abiotic stress responses; several have been identified as targets of the auxin-mimicking herbicide picloram. In this study, we identified five putative TIR1/AFB gene family members in the important vegetable crop Solanum melongena (eggplant) and characterized them using bioinformatics tools and gene expression analyses. Phylogenetic analysis of the TIR1/AFBs classified them into three subgroups based on their Arabidopsis and Solanum lycopersicum homologs. AFB6 homologs were present only in S. melongena and S. lycopersicum, whereas AFB2/3 homologs were found only in Arabidopsis. One pair of S. melongena TIR1 homologs were located in syntenic regions in the genome and appeared to have arisen by segmental duplication. Promoter analysis revealed 898 cis-elements in the TIR1/AFB promoters, 125 of which were related to hormones, stress, light, or growth responses, but only SmAFB5 had a cis-acting regulatory element involved in auxin responsiveness (AuxRR-core). RNA sequencing and expression profiling showed that the TIR1/AFB genes were differentially expressed at different growth stages and in response to light, temperature, and drought. Only SmTIR1A expression was significantly induced by picloram treatment and different growth stages. TIR1/AFB expression is regulated by microRNAs (miRNAs) in other plant species, and we identified 6 or 29 miRNAs that potentially targeted the five TIR1/AFB genes on the basis of comparisons with S. lycopersicum and S. tuberosum miRNAs, respectively. Three-dimensional protein structure predictions revealed that all the TIR1/AFB proteins were very similar in structure, differing only in the numbers of alpha helices and in one angle linking an α helix and a β sheet. For measuring the function of TIR1/AFB genes in response to drought, SmAFB5 was selected, and knockdown by virus-induced gene silence (VIGS) 35S::SmAFB5 lines showed resistance to drought compared to controls. These analyses provide insight into the potential functions of TIR1/AFBs during growth and in response to stress; they highlight differences among the SmTIR1/AFBs that may be useful for eggplant breeding.

Auxin/indole acetic acid (Aux/IAA) proteins repress the expression of auxin-responsive genes to mediate environmental abiotic stresses. Distinct auxinic herbicides are differentially involved in the auxin signaling pathway, affecting the functional role of specific Aux/IAA members. However, the role of Aux/IAA in modulating the sensitivity of eggplant (Solanum melongena L.) to the auxinic herbicide picloram remains largely unexplored. This study aims to identify putative Aux/IAA gene family members in eggplant and to characterized their functional roles in response to auxinic herbicide picloram (HRAC, group 4), offering potential molecular targets for the development of herbicide-resistant eggplant. We conducted the genome-wide identification of Aux/IAA gene family members in eggplant and analyzed their expression profiles in response to picloram. We systematically characterized the functional role of SmIAA15 in response to the herbicide picloram and uncovered the molecular mechanisms underlying SmIAA15-mediated sensitivity of eggplant to picloram using a combination of molecular and biochemical approaches. We identified twenty-three putative Aux/IAA gene family members in eggplant. Under picloram treatment, SmIAA15 was significantly induced and localized to the nucleus. Overexpression of SmIAA15 in tobacco notably decreased resistance against picloram, while virus-induced gene silencing of SmIAA15 in eggplant enhanced resistance to picloram. KEGG analysis of transcriptome data from SmIAA15-silenced lines revealed that the enhanced resistance to picloram was associated with the glutathione metabolism pathway, as evidenced by increased glutathione S-transferases (GST) enzyme activity and upregulation of GST-related genes in SmIAA15-silenced lines. Consistently, stable transgenic tomato lines overexpressing SmIAA15 displayed a picloram-induced phenotype with outwardly curved leaves, and decreased GST activity compared to the non-transgenic controls. Collectively, our findings demonstrate that SmIAA15 acts as a negative regulator in response to picloram by regulating the glutathione S-transferase enzyme activity, potentially contributing to the molecular breeding of picloram-resistant eggplant.