Strigolactones affect the root system architecture of cherry rootstock by mediating hormone signaling pathways

Abstract Strigolactones (SLs) are new phytohormones that modulate plant root growth and development. Rootstocks affect horticulturally important traits of cultivars, including tree size, abiotic stress tolerance, and disease resistance. This study focused on understanding the effects of SLs on the transcriptional regulation and root system architecture of cherry rootstock. Here, we examined the morphology and profiled endogenous hormone levels, and transcript levels of key genes from the roots treated with synthetic SLs analog GR24 or SLs inhibitor TIS108. Cherry rootstock plantlets treated with 10 μM TIS108 exhibited fewer adventitious roots (AR). The diameter of AR at 5, 10, and 30 days after 0.1 μM GR24 treatment decreased by 23.8, 23.2, and 11.5 %, respectively, whereas AR diameter was 1.15, 1.15, and 1.16 times higher than that in the control when 10 μM TIS108 was applied, respectively. The LR number in plantlets treated with 10 μM TIS108 reached a maximum of 11.25 for each AR, much higher than those of the control and other treatments at 30 days after treatment (DAT). X-ray micro-CT scanning also showed that the treatment with 10 μM TIS108 markedly induced LR initiation but suppressed LR elongation. Furthermore, 2946, 1536, and 2146 differentially expressed genes (DEGs; p-value 1) were identified in the root samples treated with 0.1 μM GR24, 10 μM GR24, and 10 μM TIS108, respectively, compared to the control. RNA-Seq findings highlighted several DEGs, such as ARF, PP2C, ERF, LOB, and CYC, which play critical roles in hormone signaling, cell cycle, and root growth and development. UPLC-MS analysis further demonstrated that SLs markedly altered the levels of endogenous hormones in cherry rootstock. In particular, the content of endogenous indole-3-acetic acid (IAA) markedly increased by 64.6, 52.1, and 173.5 % after treatment with 0.1 μM GR24, 10 μM GR24, and 10 μM TIS108, respectively. Overall, our study indicates that SLs affect root system architecture by interacting with other plant hormones, which provides a solid theoretical basis for the effects of SLs on the root system architecture of other woody plants.