Establishment of a novel infinite cycle model from hairy roots to Isatis indigotica

Plant hairy root technology provides abundant genetic resources for plant research. However, the stable preservation of excellent hairy root lines from generation to generation is crucial for research based on plant hairy root technology. Due to the random insertion of the T-DNA sequences of the Agrobacterium rhizogenes Ri plasmid into the plant genome, if excellent hairy root lines need to be induced and established using A. rhizogenes again, it is difficult to obtain the same line twice, which also increases experimental costs and time. The establishment of a new method for cultivating plant hairy roots can provide a more reliable guarantee for research on plant hairy root technology and promote research on plant hairy root technology. This study aimed to solve the problem of rebuilding excellent hairy root lines by using Isatis indigotica as a material and establishing a new cultivation method for I. indigotica hairy roots. Leaves and root segments of I. indigotica were used as explants, and A. rhizogenes R1601 was used as the infection strain to establish an infinite cycle model from hairy roots to I. indigotica plants. A genetic transformation system for hairy roots was established using leaves and root segments as explants. Hairy roots can be directly induced into adventitious buds without callus tissue and then form plants. The leaves of adventitious buds or plants can be reinduced to form hairy roots without being infected by A. rhizogenes. An infinite cycle pattern from hairy roots to plants was established. In this cycle, any stage can serve as a starting point to complete the entire cycle. The establishment of this method provides novel insight for expanding the application of plant hairy root technology.