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Low temperature is the most common abiotic stress factors during the eggplant cultivation in solar greenhouses. Melatonin plays important roles in plant resistance to low temperature. However, the role of melatonin in regulating chilling tolerance and extending the preharvest shelf life of eggplant fruits is still unknown. In this study, we investigated the effects of exogenous melatonin on eggplant plants and fruits in response to low temperature. Under simulated low-temperature conditions, exogenous melatonin significantly relieved the chilling symptoms of seedlings by reducing reactive oxygen species (ROS) and malondialdehyde (MDA) levels and relative leakage rates. These reductions were caused by higher superoxide dismutase (SOD) and catalase (CAT) activities and increased endogenous polyamine and melatonin levels compared with those in untreated seedlings. Notably, the expression levels of SOD, CAT1/2, and polyamine synthesis genes (ADC and ODC) were also increased by 100 μmol · L−1 melatonin, as well as those of genes involved in melatonin synthesis (TDC, T5H, SNAT, ASMT, and COMT) and cold regulation (COR1, CBFa/b, and ZAT2/6/12). To further investigate the effects of melatonin on eggplant leaves and fruits under natural low temperature conditions, 100 μmol · L−1 melatonin was sprayed on the functional leaves at three days before commodity maturation. Melatonin significantly alleviated chilling injury in the leaves and pericarp and extended the preharvest shelf life of the fruit by increasing the expression of COR1, CBF, ZAT2/6/12, and API5 and decreasing the expression of senescence-related genes (NCED1/2 and SAG12). Therefore, 100 μmol · L−1 melatonin improved chilling tolerance and fruit shelf life by upregulating ZAT2/6/12 to affect ROS- and senescence-related processes, which provides a reference for alleviating cold stress and extending the preharvest fruit shelf life in eggplant.

Eggplant (Solanum melongena L.) is a highly nutritious and economically important vegetable crop. However, the fruit peel of eggplant often shows poor coloration owing to low-light intensity during cultivation, especially in the winter. The less-photosensitive varieties produce anthocyanin in low light or even dark conditions, making them valuable breeding materials. Nevertheless, genes responsible for anthocyanin biosynthesis in less-photosensitive eggplant varieties are not characterized. In this study, an EMS mutant, named purple in the dark (pind), was used to identify the key genes responsible for less-photosensitive coloration. Under natural conditions, the peel color and anthocyanin content in pind fruits were similar to that of wildtype ‘14-345’. The bagged pind fruits were light purple, whereas those of ‘14-345’ were white; and the anthocyanin content in the pind fruit peel was significantly higher than that in ‘14-345’. Genetic analysis revealed that the less-photosensitive trait was controlled by a single dominant gene. The candidate gene was mapped on chromosome 10 in the region 7.72 Mb to 11.71 Mb. Thirty-five differentially expressed genes, including 12 structural genes, such as CHS, CHI, F3H, DFR, ANS, and UFGT, and three transcription factors MYB113, GL3, and TTG2, were identified in pind using RNA-seq. Four candidate genes EGP21875 (myb domain protein 113), EGP21950 (unknown protein), EGP21953 (CAAX amino-terminal protease family protein), and EGP21961 (CAAX amino-terminal protease family protein) were identified as putative genes associated with less-photosensitive anthocyanin biosynthesis in pind. These findings may clarify the molecular mechanisms underlying less-photosensitive anthocyanin biosynthesis in eggplant.

Flowering time is an important agronomic trait of Chinese cabbage with late flowering being a primary breeding objective. In our previous work, we obtained Chinese cabbage-cabbage translocation lines that contained several beneficial cabbage genes. Cabbage-specific molecular markers show that these genes were coming from chromosome C01 of cabbage. In this study, we investigated the inheritance of flowering time in a couple of translocation lines and analyzed the transmission rate of molecular markers in the offspring. Consequently, we obtained the late flowering Chinese cabbage-cabbage translocation line ‘AT7–4’ in which the flowering time was later than that of ‘85–1’ by about 7 days under 4-week vernalization. Based on previous studies of the genomes of Chinese cabbage and cabbage, we located the cabbage-specific molecular markers that were closely linked at the top of the chromosome A01 in the F2 mapping population generated by self-crossing F1s derived from a cross between the translocation line ‘AT7–4’ and Chinese cabbage ‘14–36’. Five flowering-related genes in the alien fragment were found by functional annotation and their molecular markers were developed. This study lays the foundation for the future improvement of Chinese cabbage varieties using A-C translocation lines.

Pepper mild mottle virus (PMMoV) poses a significant threat to pepper production because it is highly contagious and extremely persistent in soil. Despite this threat, little is known about the molecular processes that underlie plant responses to pepper mild mottle virus. Here, we performed RNA sequencing of tolerant (“17-p63”) and susceptible (“16-217”) pepper genotypes after pepper mild mottle virus or mock inoculation. Viral accumulation in systemic leaves was lower in the pepper mild mottle virus-resistant 17-p63 genotype than in the pepper mild mottle virus-sensitive 16-217 genotype, and infection symptoms were more apparent in systemic leaves of 16-217 than in those of 17-p63 at the same timepoints during the infection process. We identified 2,959 and 2,159 differentially expressed genes (DEGs) in systemic leaves of infected 16-217 and 17-p63, respectively. Through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of differentially expressed genes from both genotypes revealed significant enrichment of the MAPK signaling pathway, plant–pathogen interaction, and flavonoid biosynthesis. A number of differentially expressed genes showed opposite trends in relation to stress resistance and disease defense in the two genotypes. We also performed weighted gene co-expression network analysis (WGCNA) of all samples and identified modules associated with resistance to pepper mild mottle virus, as well as seven hub genes. These results identify candidate virus resistance genes and provide insight into pepper defense mechanisms against pepper mild mottle virus.

The TIR1/AFB family of proteins is a group of functionally diverse auxin receptors that are only found in plants. TIR1/AFB family members are characterized by a conserved N-terminal F-box domain followed by 18 leucine-rich repeats. In the past few decades, extensive research has been conducted on the role of these proteins in regulating plant development, metabolism, and responses to abiotic and biotic stress. In this review, we focus on TIR1/AFB proteins that play crucial roles in plant responses to diverse abiotic and biotic stress. We highlight studies that have shed light on the mechanisms by which TIR1/AFB proteins are regulated at the transcriptional and post-transcriptional as well as the downstream in abiotic or biotic stress pathways regulated by the TIR1/AFB family.

Cyclins are involved in cell division and proliferation by activating enzymes required for the cell cycle progression. Our genome-wide analysis identified 76 cyclin genes in Brassica rapa, which were divided into nine different types (A-, B-, C-, D-, H-, L-, P-, T-, and SDS-type). Cyclin genes were unevenly scattered on all chromosomes, with a maximum of 10 on A08 and a minimum of 2 on A04. The gene structure and conserved motif analysis showed that the cyclins which belonged to the same type or subgroup have a comparable intron/exon pattern or motif. A total of 14 collinear gene pairs suggested that the B. rapa cyclin genes experienced a mass of segmental duplication. The Ka/Ks analysis revealed that the Brcyclin gene family has undergone an extensive purifying pressure. By analyzing the cis-elements in the promoters, we identified 11 cis-elements and five of them are related to the hormone response. We observed 48 potential miRNAs targeting 44 Brcyclin genes, which highlighted the involvement of miRNAs in the regulation of cyclin genes. An association analysis between the leaf size and SNPs in mutants and a transcriptome analysis of two Chinese cabbage-cabbage translocation lines also showed that the Brcyclin gene family was involved in the development of the leaves. The functional characterization of the B. rapa cyclin gene family will provide the foundation for future physiological and genetic studies in the regulation of leaf growth.

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.

Purple eggplant fruits often turn brown during maturity stages, severely influencing their market value and shelf life. However, the metabolites and genes accounting for the fruit color changes are largely unknown. Here, metabolites and gene expression analyses were used to explore the candidates underlying the differences in fruit color changes between two eggplant genotypes, ‘14-345’ and ‘CGN23829’, with contrasting fruit color changes during fruit development. We found that flavonoids are the most differentially accumulated metabolites between ‘14-345’ and ‘CGN23829’. Higher contents of D3R and D3G are important for keeping the purple color at the maturity stage. Naringenin chalcone likely accounts for the color changes from purple to brown in ‘14-345’. Notably, at the physiological maturity stage, lower expression of early biosynthetic genes (EBGs) involved in the flavonoid biosynthesis pathway is important to keep lower contents of metabolites upstream of anthocyanins, thus leading to more purple coloring. Taken together, the results indicate that delphinidins and naringenin chalcone play important roles in determining eggplant fruit color changes at maturity stages, which is helpful for further dissecting the mechanisms underlying fruit color differences and changes in eggplants.

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.

Heading is a key agronomic trait of Chinese cabbage. A non-heading mutant with flat growth of heading leaves (fg-1) was isolated from an EMS-induced mutant population of the heading Chinese cabbage inbred line A03. In fg-1 mutant plants, the heading leaves are flat similar to rosette leaves. The epidermal cells on the adaxial surface of these leaves are significantly smaller, while those on the abaxial surface are much larger than in A03 plants. The segregation of the heading phenotype in the F2 and BC1 population suggests that the mutant trait is controlled by a pair of recessive alleles. Phytohormone analysis at the early heading stage showed significant decreases in IAA, ABA, JA and SA, with increases in methyl IAA and trans-Zeatin levels, suggesting they may coordinate leaf adaxial-abaxial polarity, development and morphology in fg-1. RNA-sequencing analysis at the early heading stage showed a decrease in expression levels of several auxin transport (BrAUX1, BrLAXs, and BrPINs) and responsive genes. Transcript levels of important ABA responsive genes, including BrABF3, were up-regulated in mid-leaf sections suggesting that both auxin and ABA signaling pathways play important roles in regulating leaf heading. In addition, a significant reduction in BrIAMT1 transcripts in fg-1 might contribute to leaf epinastic growth. The expression profiles of 19 genes with known roles in leaf polarity were significantly different in fg-1 leaves compared to wild type, suggesting that these genes might also regulate leaf heading in Chinese cabbage. In conclusion, leaf heading in Chinese cabbage is controlled through a complex network of hormone signaling and abaxial-adaxial patterning pathways. These findings increase our understanding of the molecular basis of head formation in Chinese cabbage.

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.

To understand the genetic regulation of the domestication trait leafy-head formation of Chinese cabbages, we exploit the diversity within Brassica rapa. To improve our understanding of the relationship between variation in rosette-leaves and leafy heads, we phenotyped a diversity set of 152 Chinese cabbages. This showed correlation between rosette-leaf traits and both head traits and heading capacity. Interestingly, the leaf number of the mature head is not correlated to heading degree nor head shape. We then chose a non-heading pak choi genotype to cross to a Chinese cabbage to generate populations segregating for the leafy head traits. Both a large F2 (485 plants) and a smaller Doubled Haploid (88 lines) mapping population were generated. A high density DH-88 genetic map using the Brassica SNP array and an F2 map with a subset of these SNPs and InDel markers was used for quantitative trait locus (QTL) analysis. Thirty-one quantitative trait loci (QTLs) were identified for phenotypes of rosette-leaves in time and both heading degree and several heading traits. On chromosome A06 in both DH-88 and F2-485 QTLs for rosette leaf length and petiole length at different developmental days and an F2 QTL for head height co-located. Variation in head height, width and weight all correlate with variation in heading degree with co-locating QTLs, respectively, on chromosome A03, A05, and A08 in F2-485. The correlation between rosette-leaf and heading traits provides not only insight in the leaf requirements to form a head, but also can be used for selection by Chinese cabbage breeders.

Chinese cabbage buds were soaked with Ethyl methanesulfonate (EMS) was used to soak to induce mutagenesis. The influence of different EMS concentrations and treatment durations on microspore development, embryo production rate and seedling rate were evaluated in five genotypes of Chinese cabbage genotypes. Mutations in four color-related genes were identified using hHigh resolution melting (HRM) curves of their PCR products. was used to identify mutations in four color-related genes. The results demonstrated that an EMS concentration greater than 0.1% was lethal to microspores. The greatest embryo production and seedling rates were observed when buds were treated with 0.03 to 0.1% EMS for 5 to 10 min, while EMS concentrations greater than 0.1% were lethal to the microspores.. These conditions also facilitated culturing of microspores. In total, 142 mutants with distinct variations in leaf shape, leaf color, corolla size, flower color, bolting time and downy mildew resistance were identified from 475 microspore culture derived Doubled Haploids plantlets. Our results suggest demonstrate that microspore derived Doubled Haploids from soaking of buds with EMS soaked buds is anrepresents an efficient approach to the rapidly generation generate of Chinese cabbage mutants.

Heading is one of the most important agronomic traits for Chinese cabbage crops. During the heading stage, leaf axial growth is an essential process. In the past, most genes predicted to be involved in the heading process have been based on leaf development studies in Arabidopsis. No genes that control leaf axial growth have been mapped and cloned via forward genetics in Chinese cabbage. In this study, we characterize the inward curling mutant ic1 in Brassica rapa ssp. pekinensis and identify a mutation in the OCTOPUS (BrOPS) gene by map-based cloning. OPS is involved in phloem differentiation in Arabidopsis, a functionalization of regulating leaf curvature that is differentiated in Chinese cabbage. In the presence of brassinosteroid (BR) at the early heading stage in ic1, the mutation of BrOPS fails to sequester brassinosteroid insensitive 2 (BrBIN2) from the nucleus, allowing BrBIN2 to phosphorylate and inactivate BrBES1, which in turn relieves the repression of BrAS1 and results in leaf inward curving. Taken together, the results of our findings indicate that BrOPS positively regulates BR signaling by antagonizing BrBIN2 to promote leaf epinastic growth at the early heading stage in Chinese cabbage. [ABSTRACT FROM AUTHOR]