Chinese cabbage is an important vegetable from both a nutritional and an economic standpoint, with the leafy head serving as the primary harvested organ. However, the nutrient accumulation as well as influencing factors within the leafy head have not yet been elucidated. Thus, the distribution of metabolites (soluble sugars, minerals, carotenoids, vitamin C, flavonoid compounds, glucosinolates, and total phenolic compounds) were investigated in different leaf layers of Chinese cabbage with varying head types. The results showed that the inner leaves consistently displayed markedly higher levels of fructose and glucose when contrasted with the outer leaves. Similarly, there was an accumulation of glucosinolates in the inner leaves. By contrast, however, the antioxidants content exhibited a consistent decline from the outer leaves towards the central core, in line with the diminishing antioxidant capacity. This descending trend was also apparent in the mineral content, encompassing calcium, sodium, magnesium and sulfur. These results will provide dietary instruction, especially for consumers who have particular dietary needs.

Glucosinolates are secondary plant metabolites that are part of the plant’s defense system against pathogens and pests and are activated via enzymatic degradation by thioglucoside glucohydrolases (myrosinases). Epithiospecifier proteins (ESPs) and nitrile-specifier proteins (NSPs) divert the myrosinase-catalyzed hydrolysis of a given glucosinolate to form epithionitrile and nitrile rather than isothiocyanate. However, the associated gene families have not been explored in Chinese cabbage. We identified three ESP and fifteen NSP genes randomly distributed on six chromosomes in Chinese cabbage. Based on a phylogenetic tree, the ESP and NSP gene family members were divided into four clades and had similar gene structure and motif composition of Brassica rapa epithiospecifier proteins (BrESPs) and B. rapa nitrile-specifier proteins (BrNSPs) in the same clade. We identified seven tandem duplicated events and eight pairs of segmentally duplicated genes. Synteny analysis showed that Chinese cabbage and Arabidopsis thaliana are closely related. We detected the proportion of various glucosinolate hydrolysates in Chinese cabbage and verified the function of BrESPs and BrNSPs in glucosinolate hydrolysis. Furthermore, we used quantitative RT-PCR to analyze the expression of BrESPs and BrNSPs and demonstrated that these genes responded to insect attack. Our findings provide novel insights into BrESPs and BrNSPs that can help further promote the regulation of glucosinolate hydrolysates by ESP and NSP to resist insect attack in Chinese cabbage.

Chinese cabbage is the most widely consumed vegetable crop due to its high nutritional value and rock-bottom price. Notably, the presence of the physiological disease petiole spot significantly impacts the appearance quality and marketability of Chinese cabbage. It is well known that excessive nitrogen fertilizer is a crucial factor in the occurrence of petiole spots; however, the mechanism by which excessive nitrogen triggers the formation of petiole spots is not yet clear. In this study, we found that petiole spots initially gather in the intercellular or extracellular regions, then gradually extend into intracellular regions, and finally affect adjacent cells, accompanied by cell death. Transcriptomic and proteomic as well as physiology analyses revealed that the genes/proteins involved in nitrogen metabolism exhibited different expression patterns in resistant and susceptible Chinese cabbage lines. The resistant Chinese cabbage line has high assimilation ability of NH₄⁺, whereas the susceptible one accumulates excessive NH₄⁺, thus inducing a burst of reactive oxygen species (ROS). These results introduce a novel perspective to the investigation of petiole spot induced by the nitrogen metabolism pathway, offering a theoretical foundation for the development of resistant strains in the control of petiole spot.

Chinese cabbage (Brassica rapa ssp. pekinensis) is one of the most widely consumed vegetables and is commonly stored postharvest. However, a physiological disorder known as petiole spot often develops during storage, significantly impairing the visual quality and marketability of the produce. Despite its economic impact, the underlying mechanisms of petiole spot formation during storage remain poorly understood. In this study, it was observed that petiole spots primarily occur in the outer leaf petioles and gradually diminish toward the inner leaves during storage. Lesions are largely restricted to the petiole, with minimal occurrence in the lamina tissue. Transcriptomic and physiological analyses revealed that genes involved in abscisic acid (ABA) biosynthesis and metabolism exhibit distinct expression patterns between healthy and lesioned tissues. Notably, the concentration of ABA and its conjugate ABA-glucose ester (ABA-GE) was significantly higher in affected regions. Further assays confirmed the role of ABA in symptom development: exogenous ABA application exacerbated lesion formation, while treatment with the ABA biosynthesis inhibitor fluridone (FLD) effectively suppressed symptom severity. Interestingly, ABA also enhanced H₂O₂-mimic petiole spot development, whereas FLD mitigated the symptoms, suggesting a synergistic interaction between ABA and reactive oxygen species (ROS) in petiole spot formation. Together, these findings demonstrate a central role for ABA–ROS crosstalk in the development of the petiole spot in stored Chinese cabbage and provide new insights for potential post-harvest intervention strategies.