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  • Author or Editor: Yan Hong x
  • Journal of the American Society for Horticultural Science x
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The light-dependent coloration of the vital organs of horticultural crops affects multiple parts of production and sales. The simplicity of the metabolic pathways of anthocyanins and the characteristics of light-dependent coloration make chrysanthemum (Chrysanthemum ×morifolium) an ideal subject for studying the mechanism of light-regulated anthocyanin biosynthesis. In this study, real-time quantitative reverse transcription–polymerase chain reaction (PCR) was used in the analysis of the expression levels of anthocyanin biosynthesis genes in C. ×morifolium ‘Reagan’. The reference genes selected were those assumed to remain at constant levels in three flower color lines at five floral developmental stages and at two light conditions. Using digital gene expression technology, we selected nine reference genes with moderate expression in the chrysanthemum ray florets at various floral developmental stages under illuminated and dark conditions as the candidate reference genes for further study. After comprehensively analyzing the stability of gene expression with three distinct statistical algorithms, geNorm, NormFinder, and qBase plus, we found that F-box and PP2A were the most stable genes in all of the samples. In addition, we analyzed the relative expression level of the CmF3H gene in different samples to verify the reference genes that we selected. This study provides a consensus list of validated reference genes that will benefit future studies of the expression of chrysanthemum genes involved in anthocyanin biosynthesis and floral development under various light conditions. Moreover, this information will also promote the molecular breeding of horticultural crops for their color modification.

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Aspergillus niger is a common pathogenic fungus causing postharvest rot of fruit and vegetable, whereas the knowledge on virulence factors is very limited. Superoxide dismutase [SOD (EC] is an important metal enzyme in fungal defense against oxidative damage. Thus, we try to study whether Cu/Zn-SOD is a virulence factor in A. niger. Cu/Zn-SOD encoding gene sodC was deleted in A. niger [MA70.15 (wild type)] by homologous recombination. The deletion of sodC led to decreased SOD activity in A. niger, suggesting that sodC did contribute to full enzyme activity. ΔsodC strain showed normal mycelia growth and sporulation compared with wild type. However, sodC deletion markedly increased the cell’s sensitivity to intracellular superoxide anion generator menadione. Besides, spore germination under menadione and H2O2 stresses were significantly retarded in ΔsodC mutant compared with wild type. Further results showed that sodC deletion induced higher superoxide anion production and higher content of H2O2 and malondialdehyde (MDA) compared with wild type, supporting the role of SOD in metabolism of reactive oxygen species (ROS). Furthermore, ΔsodC mutant had a reduced virulence on chinese white pear (Pyrus bretschneideri) as lesion development by ΔsodC was significantly less than wild type. The determination of superoxide anion, H2O2, and MDA in A. niger-infected pear showed that chinese white pear infected with ΔsodC accumulated less superoxide anion, H2O2, and MDA compared with that of wild type A. niger, implying that ΔsodC induced an attenuated response in chinese white pear during fruit–pathogen interaction. Our results indicate that sodC gene contributes to the full virulence of A. niger during infection on fruit. Aspergillus niger is one of the most common species found in fungal communities. It is an important fermentation industrial strain and is also known to cause the most severe symptoms in fruit during long-term storage (). Meanwhile, plants activate their signaling pathways to trigger defense responses to limit pathogen expansion. One of the earliest host responses after pathogen attack is oxidative burst, during which large quantities of ROS are generated by different host enzyme systems, such as glucose oxidase (). ROS such as singlet oxygen, superoxide anion, hydroxyl (OH), and H2O2 are released to hinder the advance of pathogens (). ROS can react with and damage cellular molecules, such as DNA, protein, and lipids, which will limit fungal propagation in the host plant ().

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