Plasmodiophora brassicae, a soil-borne biotroph, establishes galls as strong physiological sinks on Brassicaceae plants including Brassica napus and Arabidopsis thaliana. We compare transcriptional profiles of phloem dissected from leaf petioles and hypocotyls of healthy and infected B. napus plants. Our results highlight how pathogenesis accompanies phloem-mediated defence responses whilst exerting a strong influence on carbon-nitrogen (C-N) economy. We observe transcriptional changes indicating decreased aliphatic glucosinolate biosynthesis, fluctuating jasmonic acid responses, altered amino acid (AA) and nitrate transport, carbohydrate metabolism and modified cytokinin responses. Changes observed in phloem-dissected from upper versus lower plant organs point to phloem as a conduit in mediating C-N repartitioning, nutrition-related signalling and cytokinin dynamics over long distances during clubroot disease. To assess changes in physiology, we measured AAs, sugars and cytokinins, in phloem exudates from B. napus plants. Despite the decrease in most AA and sucrose levels, isopentyl-type cytokinins increased within infected plants. Furthermore, we employed Arabidopsis for visualising promoter activities of B. napus AA and N transporter orthologues and tested the impact of disrupted cytokinin transport during P. brassicae-induced gall formation using Atabcg14 mutants. Our physiological and microscopy studies show that the host developmental reaction to P. brassicae relies on cytokinin and is accompanied by intense nitrogen and carbon repartitioning. Overall, our work highlights the systemic aspects of host responses that should be taken into account when studying clubroot disease.

• Keywords
• Brassica napus, Plasmodiophora brassicae, clubroot, laser dissection transcriptomics, oilseed rape, phloem,
• MeSH
• Amino Acids metabolism   MeSH
• Arabidopsis * genetics   physiology   MeSH
• Brassica napus * genetics   metabolism   physiology   parasitology   MeSH
• Cyclopentanes metabolism   MeSH
• Cytokinins metabolism   MeSH
• Nitrogen metabolism   MeSH
• Phloem * metabolism   genetics   MeSH
• Glucosinolates metabolism   MeSH
• Plant Leaves genetics   metabolism   MeSH
• Plant Diseases * parasitology   genetics   MeSH
• Oxylipins metabolism   MeSH
• Plasmodiophorida * physiology   MeSH
• Gene Expression Regulation, Plant * MeSH
• Transcriptome MeSH
• Carbon metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Amino Acids MeSH
• Cyclopentanes MeSH
• Cytokinins MeSH
• Nitrogen MeSH
• Glucosinolates MeSH
• jasmonic acid MeSH Browser
• Oxylipins MeSH
• Carbon MeSH

Putrescine (Put) is a promising small molecule-based biostimulant to enhance plant growth and resilience, though its mode of action remains unclear. This study investigated the Put priming effect on Arabidopsis mutant lines (Atadc1, Atadc2, Atnata1, and Atnata2) under control conditions and salinity to understand its role in regulating plant growth. The Atadc2 mutant, characterized by reduced endogenous Put levels, showed insensitivity to Put priming without growth enhancement, which was linked to significant imbalances in nitrogen metabolism, including a high Gln/Glu ratio. Contrarily, the Atnata2 mutant exhibited significant growth improvement and upregulated AtADC2 expression, particularly under Put priming, highlighting these genes' involvement in regulating plant development. Put priming enhanced plant growth by inducing the accumulation of specific polyamines (free, acetylated, conjugated, or bound form) and improving light-harvesting efficiency, particularly in the Atnata2 line. Our findings suggest that AtNATA2 may negatively regulate Put synthesis and accumulation via AtADC2 in the chloroplast, impacting light harvesting in photosystem II (PSII). Furthermore, the Atadc2 mutant line exhibited upregulated AtADC1 but reduced AcPut levels, pointing to a cross-regulation among these genes. The regulation by AtNATA2 on AtADC2 and AtADC2 on AtADC1 could be crucial for plant growth and overall stress tolerance by interacting with polyamine catabolism, which shapes the plant metabolic profile under different growth conditions. Understanding the regulatory mechanisms involving crosstalk between AtADC and AtNATA genes in polyamine metabolism and the connection with certain SMBBs like Put can lead to more effective agricultural practices, improving plant growth, nitrogen uptake, and resilience under challenging conditions.

• MeSH
• Arabidopsis * genetics   growth & development   physiology   metabolism   MeSH
• Photosystem II Protein Complex metabolism   MeSH
• Loss of Function Mutation MeSH
• Polyamines metabolism   MeSH
• Arabidopsis Proteins * genetics   metabolism   MeSH
• Putrescine * metabolism   MeSH
• Gene Expression Regulation, Plant * MeSH
• Salt Tolerance * genetics   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Photosystem II Protein Complex MeSH
• Polyamines MeSH
• Arabidopsis Proteins * MeSH
• Putrescine * MeSH