Trichoderma crassum secrets N, N′-diacetylchitobiose and indole-3-acetic acid to enhance the fibrous root formation in P. heterophylla

Pseudostellaria heterophylla (Miq.) Pax ex Pax et Hoffm., commonly called Taizishen, is a highly esteemed and edible root-usage traditional Chinese medicine. Enhancing its fibrous root formation is imperative for augmenting yield and quality. This study employed metabolome and transcriptome profiling to investigate the plant growth promotion mechanism of Trichoderma crassum strain WMM-1–7 on P. heterophylla. Strain WMM-1–7 significantly enhanced the growth of P. heterophylla, facilitating the formation of fibrous roots. Strain WMM-1–7 significantly induced the expression of auxin response genes (AUX/IAA, GH3) and other auxin-related plant hormones response genes (GID1, PYR/PYL) in plant hormone signal transduction pathway, as well as of the genes (B-ARR, BSK, TCH4) involving cell division and enlargement. Meanwhile, the transcription factor C3H is also intricately engaged in the process of cell wall re-architecture. Further, strain WMM-1–7 reshaped the metabolites profiling cocultured with P. heterophylla. These co-induced metabolites have nine main categories: organic acids and their derivatives, organ heterocyclic compounds, and lipids and lipid-like molecules. Additionally, correlation analysis showed that 34 metabolites were significantly associated with the number of fibrous roots. Finally, both indole-3-acetic acid and N,N′-diacetylchitobiose strongly promote fibrous root formation and enhance the plant height in P. heterophylla. These results demonstrate that strain WMM-1–7 can produce multiple metabolites to promote the formation and development of the fibrous root of P. heterophylla, which provides new insights for regulating plant growth and new elicitor.