Description
Red clover (Trifolium pratense L.) is an important forage and pasture legume grown throughout temperate regions. Because it can form a symbiotic relationship with rhizobium, it is able to fix atmospheric nitrogen. Due to the high cost of nitrogen fertilizers, pasture legumes have been increasingly important in forage production settings. Red clover has not been a model legume primarily due to selfincompatibility and the associated high level of genomic heterozygosity, therefore it has not been a significant contributor in molecular or genetic studies and basic information on red clover legume/rhizobium symbiosis is lacking. Using recently annotated genomic resources, RNA-seq expression analysis and CRISPR/Cas9 mutagenesis, we characterized a number of genes that are expressed only in nodule forming roots. These include genes that encode proteins with homology to nodule-specific cysteine rich proteins (NCRs) and nodule-specific polycystin-1, lipoxygenase, alpha toxic (PLAT) domain proteins (NPDs) that are postulated to be involved in plant rhizobium interactions. Our results indicate that red clover has one of the highest numbers of expressed NCR and ATS3-like/NPD peptides currently known in the inverted-repeat lacking clade (IRLC) of legumes. Knowledge of the expression of these genes and the continued analysis of the genetic variation in red clover should aid in breeding genotypes with increased rhizobium selection specificity and increased nitrogen fixation efficiency.
Included in
Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Molecular Approaches in the Analysis of Red Clover Rhizobium Symbiosis
Red clover (Trifolium pratense L.) is an important forage and pasture legume grown throughout temperate regions. Because it can form a symbiotic relationship with rhizobium, it is able to fix atmospheric nitrogen. Due to the high cost of nitrogen fertilizers, pasture legumes have been increasingly important in forage production settings. Red clover has not been a model legume primarily due to selfincompatibility and the associated high level of genomic heterozygosity, therefore it has not been a significant contributor in molecular or genetic studies and basic information on red clover legume/rhizobium symbiosis is lacking. Using recently annotated genomic resources, RNA-seq expression analysis and CRISPR/Cas9 mutagenesis, we characterized a number of genes that are expressed only in nodule forming roots. These include genes that encode proteins with homology to nodule-specific cysteine rich proteins (NCRs) and nodule-specific polycystin-1, lipoxygenase, alpha toxic (PLAT) domain proteins (NPDs) that are postulated to be involved in plant rhizobium interactions. Our results indicate that red clover has one of the highest numbers of expressed NCR and ATS3-like/NPD peptides currently known in the inverted-repeat lacking clade (IRLC) of legumes. Knowledge of the expression of these genes and the continued analysis of the genetic variation in red clover should aid in breeding genotypes with increased rhizobium selection specificity and increased nitrogen fixation efficiency.
