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Root-associated compartments, including the rhizosphere, rhizoplane, and endosphere, live with diverse microbial communities which profoundly affect plant growth and health. However, a systematic understanding of the microbiome assembly across the rhizosphere, rhizoplane, and endosphere under pathogen invasion remains elusive. Using 16S high-throughput sequencing, we studied how bacterial wilt disease affected the variation and assembly of the three continuous root-associated microbiomes of tobacco. The results indicated that microorganisms were gradually filtered from the rhizosphere to the endosphere. With the pathogen invasion, the rhizosphere, rhizoplane and endosphere microbiomes selected and recruited different beneficial bacterial taxa. Some recruited bacteria were also identified as keystone members in networks (i.e., Bosea in the endosphere). The microbiomes of endosphere and rhizoplane were more sensitive to plant disease than the rhizosphere microbiome. Still, response strategies of the rhizoplane and endosphere to disease were obviously different. Microbial networks of the rhizoplane became complex in diseased samples and genes involved in sporulation formation and cell cycle were enriched. However, microbial networks of the diseased endosphere were disrupted, and functional genes related to nitrogen utilization and chemotaxis were significantly increased, indicating the importance of nitrogen resources supply of plants for the endosphere microbiome under pathogen invasion. Our results provide novel insights for understanding the different responses of the root-associated microbiomes to plant disease.

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Background: The Houge type of X-linked syndromic mental retardation is an X-linked intellectual disability (XLID) recently recorded in the Online Mendelian Inheritance in Man (OMIM) and only 8 cases have been reported in literature thus far. Case presentation: We present two brothers with intractable seizures and syndromic intellectual disability with symptoms consisting of delayed development, intellectual disability, and speech and language delay. The mother was a symptomatic carrier with milder clinical phenotype. Whole exome sequencing identified a small fragment deletion spanning four exons, about 9.5 kilobases (kb) in length in the CNKSR2 gene in the patients. The mutation co-segregation revealed that exon deletions occurred de novo in the proband's mother. Conclusion: Although large deletions have been reported, no small deletions have yet been identified. In this case report, we identified a small deletion in the CNKSR2 gene. This study enhances our knowledge of the CNKSR2 gene mutation spectrum and provides further information about the phenotypic characteristics of X-linked syndromic intellectual disability.

Additional index words. root, soil potassium, organic acid, root vigor, stress-resistant enzyme activity Abstract. Organic acid secretion from higher plant roots into the rhizosphere soil plays an important role in nutrient acquisition and metal detoxification; however, their precise functions and the related mechanisms in abiotic stress tolerance remain poorly understood. Tobacco is an important crop plant, so thoroughly elucidating these factors in tobacco is of high priority. In the present study, the activation effect on soil potassium (K), contents of exuded organic acids, and physiological changes in the roots of various tobacco varieties under both normal K supply and K-deficiency stress were investigated. Our results showed that one high-K variety (ND202) exhibited a significantly higher total content of organic acids in the root exudates and the highest available K content in the rhizosphere soil, compared with two common ones (K326 and NC89). Moreover, the high-K tobacco variety was less affected in terms of root vigor under K-deficiency stress, and displayed greater increases in the activities of the stress-resistant enzymes consisting of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Taken together, these results provide evidence that tobacco roots exude large amounts of organic acids to increase the available K content in the rhizosphere soil and improve the utilization rate of soil K.