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Zizania latifolia is an important aquatic vegetable, and its edible gall is induced by the fungus Ustilago esculenta . Gall development is influenced by multiple factors. Nitrogen (N) is a central determinant of plant development and crop quality, yet how N modulates gall development in Z. latifolia remains largely unclear. Here, transcriptomic, metabolomic, and physiological analyses were integrated to investigate how N deficiency affects gall development at three stages: 7, 14, and 21 days after gall swelling. The present results showed that N deficiency reduced plant height, tiller number, and gall size, but promoted root length. There were decreases in photosynthetic performance, chlorophyll fluorescence parameters, and total nitrogen content with N deficiency. Concomitantly, gall tissues exhibited reduced levels of free amino acids and soluble proteins, alongside stage-dependent accumulation of soluble sugars. Multi-omics analyses revealed that N deficiency resulted in the coordinated suppression of N assimilation pathways, including GS/GOGAT, accompanied by enhanced lignin biosynthesis. In addition, N deficiency induced changes in redox-related processes, substantially altered phytohormone signaling pathways, and modified cell wall-related metabolic processes. Overall, the present study shows that N limitation disrupts carbon–nitrogen metabolic balance and source-sink allocation, thereby constraining gall expansion, structural development, and quality development. This work provides a physiological and molecular basis for optimizing N management in this crop.
Zhang et al. (Thu,) studied this question.