Boyin Qiu

Fruit flesh thickness is one of the key factors affecting the yield and quality of bitter melon, and its regulatory mechanisms remain unclear. One thick-flesh germplasm (KF) and one thin-flesh germplasm (NF) with significantly different flesh thicknesses were screened from 70 bitter melon germplasms. Through phenotypic surveys, combined metabolomic and transcriptomic analyses, and exogenous sugar treatments, the regulatory mechanisms on flesh thickness were preliminary investigated. The results showed that flesh thickness of the two germplasms remained stable during different years and seasons. Metabolomic and transcriptomic analyses revealed that fructose and mannose metabolism pathway significantly enriched in both omics datasets. The expression of key enzyme encoding genes from this pathway exhibited various expression patterns. In KF, most genes showed significantly higher expression levels than NF, with synergistic expression predominating among genes. Soluble sugar content was positively correlated with gene expression, while HXK, SDH, and TPI activities were negatively correlated with most genes, and FBP activity was positively correlated with most genes. Genes affect carbon source metabolic flux distribution by promoting sugar synthesis and inhibiting sugar respiration consumption. Exogenous sugar treatment exhibited germplasm-specific and concentration-dependent influence of gene expression, with KF primarily showing negative feedback and NF predominantly activating expression. Fruit flesh thickness was significantly positively correlated with the synergistic high expression of sugar metabolism genes and soluble sugar accumulation. This study provides a theoretical basis for molecular improvement of bitter melon fruit flesh thickness.

As a vital appearance quality trait of broccoli, curd-surface wax powder not only affects its commercial value but also plays a key role in plant resistance to abiotic stresses. However, its formation mechanism remains unclear. Using low-wax variety CK (‘QH18’) and high-wax variety T1 (‘QHMS4’) as materials, this study systematically elucidated the molecular mechanism of wax powder formation via physiological indexes, scanning electron microscopy (SEM), targeted metabolomics, and transcriptomics. Determination of fatty acid (FA) content in broccoli flower bud tissue showed a close association between FA content and wax deposition. SEM observation revealed that T1 had significantly denser wax crystals, mainly granular, than CK. Targeted metabolomics identified 25 fatty acids in the two varieties. And the linolenic and palmitic acids, with high content and significant differences, may be key metabolites regulating wax synthesis. Integrated transcriptomics and metabolomics indicated that BolfabG, BolLACS, BolKCS1, BolKCS2 and BolMAH1 genes are involved in wax biosynthesis. Moreover, AP2/ERF-ERF transcription factor (TF)-encoding genes (BolERF018, BolERF1F.1, BolERF1F.2 and BolERF1C) played the primary role in regulating wax biosynthesis, followed by NAC (BolNAC62.1), MYB (BolMYB44), and MADS-MIKC(BolPISTILLATA). These TFs may regulate BolfabG, BolLACS, BolKCS1, BolACOX2 and BolACAA1 to affect linolenic and palmitic acid balance, altering wax precursor synthesis and accumulation, and finally leading to differences in wax morphology and content. This study reveals a “Transcription Factors–Differentially Expressed Genes–Differentially Accumulated Metabolites–Fatty Acids” (TFs-DEGs-DAMs-FA) network, providing a basis for understanding broccoli wax formation.

Insights into dynamic regulatory factors in various stages of growth and development can guide strategies for precision and targeted breeding. Bitter gourd, as a vegetable product with medicinal value, plays a role in both agricultural and medical fields. In this study, phenotypic observations, metabolomic and transcriptomic analyses, and differential gene expression patterns, along with a correlation analysis, were conducted in different stages of fruit growth and development. The results revealed that the growth rate of fruit’s fresh weight, length, diameter, and flesh thickness during the first seven days was slow, and that it then rapidly increased after the seventh day, and finally slowed once more after 17 days, indicating that the overall process followed a “slow–fast–slow” pattern. Transcriptomic and metabolomic analyses identified several differentially expressed genes and metabolites, and joint analyses revealed that each of the glycolysis/gluconeogenesis, fructose and mannose metabolism and flavonoid biosynthesis pathways individually play significant roles in the dynamic regulation of fruit growth and development during the early, middle, and late stages. Among these, 53 differentially expressed genes (DEGs) and 12 differentially expressed metabolites (DEMs) were found in these pathways. A total of 12 randomly selected DEGs were analyzed using quantitative PCR, and the results showed that gene expression levels were generally consistent with transcriptomic sequencing results, exhibiting dynamic changes with varying expression levels. Correlation analysis revealed that 11 DEMs were positively correlated with four traits except for arbutin, while eight DEGs were related to all traits, including six significantly positive and two significantly negative correlations. These findings enhance our understanding of the regulatory network governing yield and quality and provide substantial evidence to support improvements in breeding programs.