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In plants, calcineurin B-like proteins (CBL) are a unique set of calcium sensors that decode calcium signals by activating a plant-specific protein kinase family called CBL-interacting protein kinases (CIPKs). The CBL-CIPK family and its interacting complexes regulate plant responses to various environmental stimuli. Chinese cabbage (

Background Glucosinolates (GSLs) are secondary metabolites, mainly existing in Brassica vegetables. Their breakdown products have health benefits and contribute to the distinctive taste of these vegetables. Because of their high value, there is a lot of interest in developing breeding strategies to increase the content of beneficial GSLs in Brassica species. GSLs are synthesized from certain amino acids and their biological roles depend largely on the structure of their side chains. Flavin-containing monooxygenase (FMOGS-OX ) genes are involved in the synthesis of these side chains. To better understand GSL biosynthesis, we sequenced the transcriptomes of turnip (Brassica rapa var. rapa) tubers at four developmental stages (S1-S4) and determined their GSL content. Results The total GSL content was high at the early stage (S1) of tuber development and increased up to S3, then decreased at S4. We detected 61 differentially expressed genes, including five FMOGS-OX genes, that were related for GSL biosynthesis among the four developmental stages. Most of these genes were highly expressed at stages S1 to S3, but their expression was much lower at S4. We estimated the effect of the five FMOGS-OX genes on GSL content by overexpressing them in turnip hairy roots and found that the amount of aliphatic GSLs increased significantly in the transgenic plants. Conclusion The transcriptome data and characterization of genes involved in GSL biosynthesis, particularly the FMOGS-OX genes, will be valuable for improving the yield of beneficial GSLs in turnip and other Brassica crops. © 2019 Society of Chemical Industry.

Callose is a β-1,3-glucan commonly found in higher plants that plays an important role in regulating plant pollen development. It is synthesized by glucan synthase-like (GSL) and is degraded by the enzyme endo-1,3-β-glucosidase. However, genome-wide analyses of callose GSL and endo-1,3-β-glucosidase enzymes in fertile and sterile flower buds of Chinese cabbage have not yet been reported. Here, we show that delayed callose degradation at the tetrad stage may be the main cause of microspore abortion in Chinese cabbage with nuclear sterility near-isogenic line '10L03'. Fifteen callose GSLs and 77 endo-1,3-β-glucosidase enzymes were identified in Chinese cabbage. Phylogenetic, gene structural and chromosomal analyses revealed that the expansion occurred due to three polyploidization events of these two gene families. Expression pattern analysis showed that the GSL and endo-1,3-β-glucosidase enzymes are involved in the development of various tissues and that the genes functionally diverged during long-term evolution. Relative gene expression analysis of Chinese cabbage flowers at different developmental stages showed that high expression of the synthetic enzyme BraA01g041620 and low expression of AtA6-homologous genes (BraA04g008040, BraA07g009320, BraA01g030220 and BraA03g040850) and two other genes (BraA10g020080 and BraA05g038340) for degrading enzymes in the meiosis and tetrad stages may cause nuclear sterility in the near-isogenic line '10L03'. Overall, our data provide an important foundation for comprehending the potential roles of the callose GSL and endo-1,3-β-glucosidase enzymes in regulating pollen development in Chinese cabbage.

Background In the agricultural areas of Qinghai-Tibet Plateau, temperature varies widely from day to night during the growing season, which makes the extreme temperature become one of the limiting factors of crop yield. Turnip (Brassica rapa var. rapa) is a traditional crop of Tibet grown in the Tibet Plateau, but its molecular and metabolic mechanisms of freezing tolerance are unclear. Results Here, based on the changes in transcriptional and metabolic levels of Tibetan turnip under freezing treatment, the expression of the arginine decarboxylase gene BrrADC2.2 exhibited an accumulative pattern in accordance with putrescine content. Moreover, we demonstrated that BrrICE1.1 (Inducer of CBF Expression 1) could directly bind to the BrrADC2.2 promoter, activating BrrADC2.2 to promote the accumulation of putrescine, which was verified by RNAi and overexpression analyses for both BrrADC2.2 and BrrICE1.1 using transgenic hair root. The function of putrescine in turnip was further analyzed by exogenous application putrescine and its inhibitor DL-α-(Difluoromethyl) arginine (DFMA) under freezing tolerance. In addition, the BrrICE1.1 was found to be involved in the ICE1-CBF pathway to increase the freezing stress of turnip. Conclusions BrrICE1.1 could bind the promoter of BrrADC2.2 or CBFs to participate in freezing tolerance of turnip by transcriptomics and targeted metabolomics analyses. This study revealed the regulatory network of the freezing tolerance process in turnip and increased our understanding of the plateau crops response to extreme environments in Tibet.

Glucosinolates (GSLs) are secondary metabolites, mainly existing in Brassica vegetables. Their breakdown products have health benefits and contribute to the distinctive taste of these vegetables. Because of their high value, there is a lot of interest in developing breeding strategies to increase the content of beneficial GSLs in Brassica species. GSLs are synthesized from certain amino acids and their biological roles depend largely on the structure of their side chains. Flavin-containing monooxygenase (FMOThe total GSL content was high at the early stage (S1) of tuber development and increased up to S3, then decreased at S4. We detected 61 differentially expressed genes, including five FMOThe transcriptome data and characterization of genes involved in GSL biosynthesis, particularly the FMO