Phytophthora parasitica is a devastating oomycete pathogen that causes significant crop losses worldwide. Identifying master regulators of its virulence is crucial for the development of novel control strategies. Here, we demonstrate that the conserved eukaryotic kinase TOR (target of rapamycin) is essential for both growth and pathogenicity in P. parasitica. Transcriptomic analysis revealed that PpTOR inhibition broadly reprograms the transcriptome of P. parasitica, notably leading to the downregulation of numerous PpRxLR and PpCRN effector genes. Among these genes, the overexpression of PpRxLR3 increased plant susceptibility to P. parasitica by affecting jasmonic acid biosynthesis and signaling. On the basis of the crucial role of PpTOR, we evaluated its potential as a target for intervention. Host-induced gene silencing (HIGS) of PpTOR in Nicotiana benthamiana conferred strong resistance to P. parasitica, which was associated with the downregulation of the expression of PpTOR and key effector genes during P. parasitica infection. Furthermore, small RNA sequencing confirmed the production of PpTOR-specific siRNAs in HIGS plants. Exogenous application of synthetic siRNAs targeting PpTOR effectively reduced P. parasitica virulence. Our findings establish PpTOR as a global regulator of pathogenicity and validate PpTOR as a promising target for RNA-based disease control strategies.
Bing-Ru Wang, Ying-Hui He, Zexuan Li et al.· Horticulturae· 0 citations
Root hairs are tubular protrusions of root epidermal cells that expand the root surface area to facilitate water and nutrient uptake. The target of rapamycin (TOR) kinase has been identified as a positive regulator of root hair elongation, and the RHD6-RSL4 bHLH transcriptional cascade is well established as a core module that governs root hair morphogenesis. However, whether TOR signaling acts upstream of the RHD6-RSL4 pathway and how glucose signals are integrated into this transcriptional regulatory network during root hair development remain incompletely understood. In this study, transcriptome profiling combined with pharmacological and genetic functional assays was performed to elucidate the TOR-mediated transcriptional regulatory pathway of root hair elongation in Arabidopsis. Chemical inhibition of TOR triggered genome-wide transcriptional reprogramming in seedling roots, including disruption of auxin and ethylene signal transduction and pronounced downregulation of hundreds of genes related to root hair development. Glucose-activated TOR signaling modulates the expression of root hair-specific (RHS) genes mainly through the core RHD6-RSL4 transcriptional cascade. The transcription of RSL1–RSL5 was strongly dependent on functional TOR activity, whereas RHD6 transcript abundance was specifically induced by glucose–TOR signaling under carbon-starvation recovery conditions. Genetic overexpression of either RHD6 or RSL4 partially rescued root hair elongation defects caused by TOR suppression, confirming that the RHD6-RSL4 cascade functions as a critical downstream transcriptional module of glucose–TOR signaling. Collectively, this work establishes a transcriptional framework in which glucose–TOR signals modulate root hair elongation via transcriptional activation of the master bHLH regulators RHD6 and RSL4.
Bing-Ru Wang, Jue Zhang, Wei Yan et al.· Plants· 0 citations
