Wenjing Yang

Indolic glucosinolates are a group of plant secondary metabolites found in Brassica vegetables, and their breakdown products could act as important anti-cancer and defense compounds against biotic stresses. Transcriptional regulation plays a key role in modulating the biosynthesis of indolic glucosinolates in the model plant Arabidopsis, but little is known about the transcriptional regulatory landscape of these glucosinolates in Brassica vegetables. In this study, we selected and functionally validated the important biosynthetic gene BolCYP83B1 from the indolic glucosinolate pathway in cabbage. Through a yeast one-hybrid assay, we systemically screened and identified upstream regulators of BolCYP83B1 in cabbage with BolANTs as the top candidates for further functional validation. Two homologs of BolANTs, BolANT1 and BolANT3, were confirmed to bind the promoter of BolCYP83B1 via both a yeast one-hybrid assay and an LUC assay. The overexpression of BolANT3 in cabbage significantly increased the accumulation of indolic glucosinolates, while the virus-induced gene silencing (VIGS) of BolANT3 significantly reduced the accumulation of indolic glucosinolates in cabbage. Our work provides valuable insights into the transcriptional regulatory mechanisms of indolic glucosinolates in Brassica vegetables.

Aliphatic glucosinolates are an abundant group of plant secondary metabolites in Brassica vegetables, with some of their degradation products demonstrating significant anti-cancer effects. The transcription factors MYB28 and MYB29 play key roles in the transcriptional regulation of aliphatic glucosinolates biosynthesis, but little is known about whether BoMYB28 and BoMYB29 are also modulated by upstream regulators or how, nor their gene regulatory networks. In this study, we first explored the hierarchical transcriptional regulatory networks of MYB28 and MYB29 in a model plant, then systemically screened the regulators of the three BoMYB28 homologs in cabbage using a yeast one-hybrid. Furthermore, we selected a novel RNA binding protein, BoRHON1, to functionally validate its roles in modulating aliphatic glucosinolates biosynthesis. Importantly, BoRHON1 induced the accumulation of all detectable aliphatic and indolic glucosinolates, and the net photosynthetic rates of BoRHON1 overexpression lines were significantly increased. Interestingly, the growth and biomass of these overexpression lines of BoRHON1 remained the same as those of the control plants. BoRHON1 was shown to be a novel, potent, positive regulator of glucosinolates biosynthesis, as well as a novel regulator of normal plant growth and development, while significantly increasing plants’ defense costs.

Chinese cabbage (Brassica rapa L. ssp. pekinensis) is an important leafy vegetable crop cultivated worldwide. Drought is one of the most important limiting factors for the growth, production and quality of Chinese cabbage due to its weak drought tolerance. In order to deepen the understanding of drought stress response in Chinese cabbage, metabolomics studies were conducted in drought−tolerant (DT) and drought−susceptible (DS) genotypes of Chinese cabbage under water deficit−simulated mild and severe drought stress conditions. A total of 777 metabolites were detected, wherein 90 of them were proposed as the drought−responsive metabolites in Chinese cabbage, with abscisic acid (ABA), serine, choline alfoscerate, and sphingosine as potential representative drought stress biomarkers. We also found that drought−tolerant and drought−susceptible genotypes showed differential metabolic accumulation patterns with contrasting drought response mechanisms. Notably, constitutively high levels of ABA and glutathione were detected in drought−tolerant genotype in all tested and control conditions. In addition, proline, sucrose, γ−aminobutyric acid, and glutathione were also found to be highly correlated to drought tolerance. This study is the first metabolomic study on how Chinese cabbage responds to drought stress, and could provide insights on how to develop and cultivate new drought−resistant varieties.