Insights into glucosinolate accumulation and metabolic pathways in Isatis indigotica Fort.

Background: Glucosinolates (GSLs) play important roles in defending against exogenous damage and regulating physiological activities in plants. However, GSL accumulation patterns and molecular regulation mechanisms are largely unknown in Isatis indigotica Fort. Results: Ten GSLs were identified in I. indigotica, and the dominant GSLs were epiprogoitrin (EPI) and indole-3-methyl GSL (I3M), followed by progoitrin (PRO) and gluconapin (GNA). The total GSL content was highest (over 20 mu mol/g) in reproductive organs, lowest (less than 1.0 mu mol/g) in mature organs, and medium in fresh leaves (2.6 mu mol/g) and stems (1.5 mu mol/g). In the seed germination process, the total GSL content decreased from 27.2 mu mol/g (of seeds) to 2.7 mu mol/g (on the 120th day) and then increased to 4.0 mu mol/g (180th day). However, the content of indole GSL increased rapidly in the first week after germination and fluctuated between 1.13 mu mol/g (28th day) and 2.82 mu mol/g (150th day). Under the different elicitor treatments, the total GSL content increased significantly, ranging from 2.9-fold (mechanical damage, 3 h) to 10.7-fold (MeJA, 6 h). Moreover, 132 genes were involved in GSL metabolic pathways. Among them, no homologs of AtCYP79F2 and AtMAM3 were identified, leading to a distinctive GSL profile in I. indigotica. Furthermore, most genes involved in the GSL metabolic pathway were derived from tandem duplication, followed by dispersed duplication and segmental duplication. Purifying selection was observed, although some genes underwent relaxed selection. In addition, three tandem-arrayed GSL-OH genes showed different expression patterns, suggesting possible subfunctionalization during evolution. Conclusions: Ten different GSLs with their accumulation patterns and 132 genes involved in the GSL metabolic pathway were explored, which laid a foundation for the study of GSL metabolism and regulatory mechanisms in I. indigotica.

Automated summary

This study identified 10 different glucosinolates (GSLs) and explored their accumulation patterns in Isatis indigotica Fort. Additionally, 132 genes involved in the GSL metabolic pathway were discovered. These findings provide a foundation for further research on GSL metabolism and regulatory mechanisms in I. indigotica.