Nitrogen enrichment shifts functional genes related to nitrogen and carbon acquisition in the fungal community. (August 2018)

• Record Type: Journal Article
• Authors: Treseder, Kathleen K.; Berlemont, Renaud; Allison, Steven D.; Martiny, Adam C.
• Is Part Of: Soil biology and biochemistry. Volume 123(2018)
• Page Start: 87
• Page End: 96
• Publication Date: 2018-08
• Subjects: Amino acid permease genes -- Ammonium transporter genes -- Fungal functional genes -- Lytic polysaccharide monooxygenase family AA9 genes -- Microbial community composition -- Nitrogen enrichment; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2018.05.014
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: To better understand mechanisms of carbon (C) and nitrogen (N) dynamics under anthropogenic N enrichment, we examined frequencies of C- and N-targeting genes in litter fungi. In particular, we tested the hypothesis that N enrichment selects for C-targeting genes but against N-targeting genes, if fungi preferentially invest resources in acquisition of growth-limiting nutrients. We conducted a fully-factorial litter and microbial transplant in a N fertilization experiment in Southern California grassland. The transplant design enabled us to contrast direct effects of N fertilization in the environment, indirect effects of N-induced shifts in the microbial community, and indirect effects of N-induced changes in plant litter chemistry. For each treatment, we assessed frequencies of select well-annotated fungal functional genes: cellulose-targeting AA9 genes (for C acquisition) versus ammonium transporter genes and amino acid permease genes (for N acquisition). We found that our hypothesis was upheld only with regard to shifts in the microbial community. Specifically, when grown in the same environment and litter, fungi from the N-fertilized plots displayed greater frequencies of cellulose-targeting AA9 genes from basidiomycetes, but smaller frequencies of ammonium transporter genes and amino acid permease genes, when compared to fungi from the control plots. In contrast, N fertilization in the plot environment was associated with higher frequencies of amino acid permease genes and ammonium transporter genes. Likewise, plant litter from the N-fertilized plots selected for higher frequencies of ammonium transporter genes. Altogether, we found fairly inconsistent effects of N enrichment on fungal functional genes related to C and N acquisition. Even if the genetic capacity of the fungal community to acquire C versus N changes owing to shifts in the microbial community, direct effects of N fertilization and indirect effects of litter chemistry may offset the response. Highlights: Nitrogen enrichment shifts functional genes related to nitrogen and carbon acquisition in the fungal community. We examined fungal genetic capacity to contribute to N and C cycling under N enrichment. Within fungal community, C-targeting genes increased; N-targeting genes declined. However, changes in litter chemistry and the plot environment offset this shift.