Multiple Group I Introns in the Small-Subunit rDNA of Botryosphaeria dothidea: Implication for Intraspecific Genetic Diversity

Botryosphaeria dothidea is a widespread and economically important pathogen on various fruit trees, and it often causes die-back and canker on limbs and fruit rot. In characterizing intraspecies genetic variation within this fungus, group I introns, rich in rDNA of fungi, may provide a productive region for exploration. In this research, we analysed complete small subunit (SSU) ribosomal DNA (rDNA) sequences of 37 B. dothidea strains, and found four insertions, designated Bdo.S943, Bdo.S1199-A, Bdo.S1199-B and Bdo.S1506, at three positions. Sequence analysis and structure prediction revealed that both Bdo.S943 and Bdo.S1506 belonged to subgroup IC1 of group I introns, whereas Bdo.S1199-A and Bdo.S1199-B corresponded to group IE introns. Moreover, Bdo.S1199-A was found to host an open reading frame (ORF) for encoding the homing endonuclease (HE), whereas Bdo.S1199-B, an evolutionary descendant of Bdo.S1199-A, included a degenerate HE. The above four introns were novel, and were the first group I introns observed and characterized in this species. Differential distribution of these introns revealed that all strains could be separated into four genotypes. Genotype III (no intron) and genotype IV (Bdo.S1199-B) were each found in only one strain, whereas genotype I (Bdo.S1199-A) and genotype II (Bdo.S943 and Bdo.S1506) occurred in 95% of the strains. There is a correlation between B. dothidea genotypes and hosts or geographic locations. Thus, these newly discovered group I introns can help to advance understanding of genetic differentiation within B. dothidea.     

The in vivo distribution of murine lymphokine activated killer cells in splenectomized host

The in vivo distribution of intravenously injected lymphokine activated killer (LAK) cells, generated in vitro with rIL-2 from normal murine splenocytes, was studied in BALB/c mice and compared with that of normal splenocytes. Both normal splenocytes and LAK cells were labeled with 51Cr, and the results were analyzed at 6, 24, and 48 hours after injection by localization index as the parameter. After injection through tail veins of mice, LAK cells were found to migrate to the spleen, lungs, liver, lymph nodes, bones and the kidneys. The apparent increased distribution pattern of LAK cells to the lung at 6 and 24 hours after injection was not detected when normal splenocytes were injected. Since almost one third of the injected LAK cells were found to localize in the spleen, it was postulated that splenectomy would affect the in vivo organ distribution of LAK cells. Accordingly, the in vivo distribution of LAK cells in splenectomized mice was further investigated. Results indicated that splenectomy enhanced the convergence of LAK cells to the lungs, liver, lymph nodes and bones. Therefore, splenectomy may augment the therapeutic effect of the adoptive transfer of LAK cells in pulmonary, hepatic, lymph node and bony metastases.     

Exosomal transfer of miR-106a-5p contributes to cisplatin resistance and tumorigenesis in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC), a subclass of cancers of the neck and head, is a predominant cause of cancer-associated death worldwide. Hence, there is a critical need for research into NPC-related treatment strategies. Cisplatin is a promising therapy option for NPCs and other cancers that is frequently utilized. Some patients acquire resistance to cisplatin therapy, which complicates the successful use of cisplatin treatment in NPCs. Although exosomal transfer of oncogenic miRNAs has been shown to improve recipient cell proliferation, metastasis and chemoresistance, the molecular mechanism behind this effect on NPC has yet to be fully understood. Exosomal microRNAs (miRNAs) from cisplatin-resistant cells were identified as significant mediators of chemoresistance in NPC cells in this investigation. Initially, we found that exosomal miR-106a-5p levels in the serum of chemoresistant and last-cycle patients were greater than in that of non-resistant and first-cycle patients. Also, exosomal miR-106a-5p enhanced the proliferative ability of NPC cells. Mechanistically, exosomal miR-106a-5p targets ARNT2, which further activates AKT phosphorylation, and thus promotes NPC cell proliferation, decreases apoptosis and in turn regulates tumorigenesis. We found similar results using in vivo NPC models, where exosomal miR-106a-5p through regulation of ARNT2 (aryl hydrocarbon receptor nuclear translocator 2) promoted tumorigenesis. Taken together, these findings indicate that exosomal miR-106a-5p could be a promising diagnostic biomarker and drug target for patients with NPC.     

Diazotroph abundance and community composition in an acidic soil in response to aluminum-tolerant and aluminum-sensitive maize (Zea mays L.) cultivars under two nitrogen fertilizer forms

Plant and Soil - In acidic soil, plant aluminum (Al) tolerance and nitrogen (N) fertilizer form play the important roles in influencing plant growth. Diazotrophs as plant growth promoting...     

Genome-wide analysis and expression profiling of PP2C clade D under saline and alkali stresses in wild soybean and <Emphasis Type="Italic">Arabidopsis</Emphasis>

Protein phosphatase 2Cs (PP2Cs) belong to the largest protein phosphatase family in plants. Some members have been described as being negative modulators of plant growth and development, as well as responses to hormones and environmental stimuli. However, little is known about the members of PP2C clade D, which may be involved in the regulation of signaling pathways, especially in response to saline and alkali stresses. Here, we identified 13 PP2C orthologs from the wild soybean (Glycine soja) genome. We examined the sequence characteristics, chromosome locations and duplications, gene structures, and promoter cis-elements of the PP2C clade D genes in Arabidopsis and wild soybean. Our results showed that GsPP2C clade D (GsAPD) genes exhibit more gene duplications than AtPP2C clade D genes. Plant hormone and abiotic stress-responsive elements were identified in the promoter regions of most PP2C genes. Moreover, we investigated their expression patterns in roots, stems, and leaves. Quantitative real-time PCR analyses revealed that the expression levels of representative GsPP2C and AtPP2C clade D genes were significantly influenced by alkali and salt stresses, suggesting that these genes might be associated with or directly involved in the relevant stress signaling pathways. Our results established a foundation for further functional characterization of PP2C clade D genes in the future.     

Mapping and characterization of the new adult plant leaf rust resistance gene <Emphasis Type="Italic">Lr77</Emphasis> derived from Santa Fe winter wheat

Key message

A new gene for adult plant leaf rust resistance in wheat was mapped to chromosome 3BL. This gene was designated as Lr77.

Abstract

‘Santa Fe’ is a hard red winter cultivar that has had long-lasting resistance to the leaf rust fungus, Puccinia triticina. The objective of this study was to determine the chromosome location of the adult plant leaf rust resistance in Santa Fe wheat. A partial backcross line of ‘Thatcher’ (Tc) wheat with adult plant leaf rust resistance derived from Santa Fe was crossed with Thatcher to develop a Thatcher//Tc*2/Santa Fe F₆ recombinant inbred line (RIL) population. The RIL population and parental lines were evaluated for segregation of leaf rust resistance in three field plot tests and in an adult plant greenhouse test. A genetic map of the RIL population was constructed using 90,000 single-nucleotide polymorphism (SNP) markers with the Illumina Infinium iSelect 90K wheat bead array. A significant quantitative trait locus for reduction of leaf rust severity in all four tests was found on chromosome 3BL that segregated as a single adult plant resistance gene. The RILs with the allele from the resistant parent for SNP marker IWB10344 had lower leaf rust severity and a moderately resistant to moderately susceptible response compared to the susceptible RILs and Thatcher. The gene derived from Santa Fe on chromosome 3BL was designated as Lr77. Kompetitive allele-specific polymerase chain reaction assay markers linked to Lr77 on 3BL should be useful for selection of wheat germplasm with this gene.