Comparative transcriptome analysis between <i>Solanum lycopersicum</i> L. and <i>Lotus japonicus</i> L. during arbuscular mycorrhizal development

<p>Arbuscular mycorrhizal (AM) fungi form symbiotic associations with diverse plant species. The AM fungi enhance mineral uptake from the soil, which benefits the growth of the host plants. Previous microarray and RNA-seq analyses have identified a large number of AM-responsive plant genes. However, little is known whether the gene expression profile of mycorrhiza is different among genetically distant plant species. The aim of this study was to assess the conservation and divergence of AM-responsive genes between two different hosts, <i>Solanum lycopersicum</i> L. and <i>Lotus japonicus</i> L., during AM development using RNA-seq data. In each host plant, gene expression was compared between AM roots and non-mycorrhizal (NM) roots. Potential orthologs of AM-responsible genes between <i>S. lycopersicum</i> and <i>L. japonicus</i> were identified with reciprocal BLAST searches. Only one quarter to one third of the AM-inducible genes in each plant species were co-upregulated in both species. The co-upregulated genes included those known to be essential for AM development and function. The co-upregulated genes exhibited a wide range of fold changes in the AM symbiosis, and the fold change value for individual co-upregulated genes was positively correlated between the two hosts. Most of the species-dependent upregulated genes exhibited low levels of induction. We also analyzed gene expression in AM fungi colonizing roots of <i>S. lycopersicum</i> and <i>L. japonicus</i>. Overall, the gene expression profiles of <i>Rhizophagus irregularis</i> were similar among the roots of the two different hosts, although hundreds of fungal genes were differentially expressed between the two hosts. In particular, genes related to the mitochondrial electron transport chain were highly expressed in AM fungi colonizing <i>L. japonicus</i> roots, indicating that adenosine triphosphate (ATP) production was enhanced in the <i>L. japonicus</i>–<i>R. irregularis</i> symbiosis. Overall, these results show that a certain proportion of AM-responsive genes is conserved across plant species. The species-dependent AM-responsive genes may be related to the physiological differences between AM and NM roots in each plant species.</p

A putative TetR-type transcription factor AZC_3265 from the legume symbiont <i>Azorhizobium caulinodans</i> represses the production of R-bodies that are toxic to eukaryotic cells

<p><i>Azorhizobium caulinodans</i> ORS571 is a microsymbiont of the legume <i>Sesbania rostrata</i>, which forms nitrogen-fixing nodules on stems and roots. This bacterium harbors a <i>reb</i> operon, which is associated with R-body production. R-bodies are large proteinaceous ribbons and were first observed in <i>Caedibacter</i> species, which are obligate bacterial endosymbionts in paramecia. R-body-producing <i>Caedibacter</i> species released from their host paramecia are toxic to the symbiont-free paramecia. R-body-producing cells of <i>A. caulinodans</i> mutants are also toxic to the plant host cells. To maintain harmonic symbiosis with <i>S. rostrata, A. caulinodans</i> has to repress the expression of the <i>reb</i> operon. To date, it has been revealed that the PraR transcription factor and Lon protease repress <i>reb</i> operon expression, in direct and indirect manners, respectively. In this study, we carried out transposon-based mutagenesis screening, and found that the AZC_3265 (locus tag on the genome) gene encoding a putative TetR-type transcription factor was involved in the repression of <i>reb</i> operon expression. The AZC_3265 gene deletion mutant showed high levels of <i>reb</i> operon expression and R-body formation, and this strain formed stem nodules defective in nitrogen-fixing activity. Systematic evolution of ligands by exponential enrichment (SELEX) experiment revealed that AZC_3265 protein could bind to the consensus palindromic sequence TTGC-N6-GCAA. However, this consensus sequence was not found in the <i>reb</i> operon promoter region. Additionally, an electrophoretic mobility shift assay (EMSA) also revealed that AZC_3265 could not bind to the <i>reb</i> operon promoter region. These results suggested that AZC_3265 repressed the expression of the <i>reb</i> operon in an indirect manner. In conclusion, the present data demonstrated that multiple regulators participate in the regulation of expression of the <i>reb</i> operon. The presence of multiple mechanisms for regulating the expression of the <i>reb</i> operon suggested that its expression was controlled in response to multiple biological and environmental factors.</p

Univariate and multivariate Cox regression analysis for disease-free survival in patients with stage II and III colorectal cancer.

<p>Univariate and multivariate Cox regression analysis for disease-free survival in patients with stage II and III colorectal cancer.</p

Univariate and multivariate Cox regression analysis for disease-free survival in patients with stage II and III colorectal cancer according to FUT8 expression and the p53 status.

<p>Univariate and multivariate Cox regression analysis for disease-free survival in patients with stage II and III colorectal cancer according to FUT8 expression and the p53 status.</p

Clinicopathological characteristics of colorectal cancer patients according to FUT8 expression.

<p>Clinicopathological characteristics of colorectal cancer patients according to FUT8 expression.</p

Representative images of immunohistochemistry for FUT8 and p53 expression in colorectal cancer.

<p>(A) FUT8 protein expression in colon carcinoma [T] and adjacent colon mucosa [N]. (B) FUT8 was not expressed by non-neoplastic colon mucosal cells. (C) FUT8 staining was typically found in cytoplasm of tumor cells. (D) Occasionally, concomitant cytoplasmic and membranous staining of FUT8 in tumor cells can be found. (E) p53-positive tumor showing strong nuclear staining in cancer cells. (F) p53-negative tumor showing no nuclear staining. Magnification: (A,E,F) x100; (B,C,D) x400.</p

Prognostic role of FUT8 expression in relation to p53 status in stage II and III colorectal cancer

<div><p>The expression of fucosyltransferase 8, an enzyme responsible for core fucosylation encoded by FUT8, influences tumor biology and correlates with patient prognosis in several solid cancers. We hypothesized that p53 alteration modifies prognostic associations of FUT8 expression in colorectal cancer (CRC), since FUT8 has recently been identified as a direct transcriptional target of wild-type p53. Utilizing multiple datasets of microarray and RNA sequence of CRC, FUT8 mRNA was found to be highly expressed in wild-type p53 tumors (n = 382) compared to those of mutant p53 (n = 437). Prognostic values of FUT8 expression in conjunction with the p53 status for disease-free survival (DFS) were analyzed using two independent cohorts of stage II and III CRC after curative surgery, including the immunohistochemistry (IHC) cohort (n = 123) and the microarray cohort (n = 357). In both cohorts, neither FUT8 expression nor the p53 status was associated with DFS. Strikingly, positive expression of FUT8 protein was significantly associated with better DFS only in tumors with negative p53, while it had no prognostic impact in tumors with positive p53 in the IHC cohort. Although not statistically significant, a similar prognostic trend was observed in the microarray cohort when patients were stratified by the p53 status. Our results suggest that the prognostic values of FUT8 expression on DFS may be modified by the p53 status, and the expression of FUT8 protein can be a prognostic biomarker for patients with stage II and III CRC.</p></div

The expression of FUT8 mRNA in multiple cohorts of colorectal cancer.

<p>(A) FUT8 mRNA expression was significantly upregulated in primary tumors compared to normal colon mucosa. (B) In five independent datasets of colorectal cancer, higher levels of FUT8 mRNA expression were consistently observed in tumors with wild-type p53 than those of mutant p53.</p