Abstract
Sheepgrass (Leymus chinensis) is one of the dominant grass species present on typical steppes of the Inner Mongolia Plateau. However, L. chinensis has developed a dwarfing phenotype in response to the stressful habitat in grasslands that are severely degraded due to heavy grazing. The lack of transcriptomic and genomic information has prohibited the understanding of the transgenerational effect on physiological alterations in clonal L. chinensis at the molecular level in response to livestock grazing. To solve this problem, transcriptomic information from the leaves of clonal L. chinensis obtained from overgrazed (GR) and non-grazed (NG) grasslands was studied using a paired-end Illumina HiSeq 2500 sequencing platform. First, despite the influence of grazing being absent during the growth of clonal offspring in our hydroponic experiment, compared with those from the NG group, clonal L. chinensis from the GR group exhibited significant dwarf-type morphological traits. A total of 116,356 unigenes were subsequently generated and assembled de novo, of which 55,541 could be annotated to homologous matches in the NCBI non-redundant (Nr), Swiss-Prot, Clusters of Orthologous Groups (COG), gene ontology (GO), or Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The expression of 3,341 unigenes significantly differed between the GR group and the NG group with an absolute value of Log2 ratio ≥ 1. The altered expression of genes involved in defence and immune responses, pathogenic resistance and cell development indicates that livestock grazing induces a transgenerational effect on the growth inhibition of clonal L. chinensis. The results of the present study will provide important large-scale transcriptomic information on L. chinensis. Furthermore, the results facilitated our investigation of grazing-induced transgenerational effects on both the morphological and physiological characteristics of L. chinensis at the molecular levels.
Highlights
The grassland on the Inner Mongolian steppe is the most important region for the production of forage, mutton, and milk in China; the region covers 68% of the total land area of the Inner Mongolia Autonomous Region[1,2]
Our previous research on clonal transgenerational effects on grassland plants indicated that significant differences in leaf photosynthesis in L. chinensis subjected to long-term overgrazing or non-grazing were maintained in the clonal offspring in a greenhouse experiment designed to remove the maternal environment[21]
Overgrazing is a frequent stress for pasture and prairie plants and is the primary factor responsible for the current deterioration on the Inner Mongolian steppe[24]
Summary
The grassland on the Inner Mongolian steppe is the most important region for the production of forage, mutton, and milk in China; the region covers 68% of the total land area of the Inner Mongolia Autonomous Region[1,2]. The major factor causing these problems is overgrazing, which threatens the sustainable development of grassland ecosystems[2,3,4] Both the quality of forage and animal products decrease due to the effect of overgrazing[5]. In response to animal grazing, steppe plants tend to exhibit resistance capabilities that affect growth performance, life history and biomass allocation[7,8,9,10]. These adaptations are a result of genotype × environment interactions and can be passed down to progeny (referred to as transgenerational effects or stress-induced memory). The objective of this study was to use an Illumina HiSeq 2500 sequencing platform to understand the relative transcriptional changes in the leaf transcriptome of clonal L. chinensis plants in which the maternal plant was grown under conditions of either long-term grazing or non-grazing
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