Genome-wide identification of mlo genes in the cultivated peanut (Arachis hypogaea L.)

Powdery mildew disease caused by Oidium arachidis poses a threat to peanut production in Africa. Loss of function mutants of specific Mlo (Mildew Locus O) genes have provided broad-spectrum and durable resistance against pathogen in many crop species. Since there is huge potential to utilize susceptibility gene-mediated resistance in crop improvement, genome-wide mining of susceptibility genes is required for further researches. However, the susceptibility genes have not been characterized in peanut genome. In this research study, the genome of the cultivated peanut was used as reference to identify the AhMlo loci. Our results revealed that 25 AhMlo loci were identified and distributed on the chromosomes of the cultivated peanut. Eleven AhMlo loci were located on the A-genome while the remaining 14 on the B-genome. Variable number of inserted intron sequences (4-14) and transmembrane helix (4-8) were observed in the coding sequence of the AhMlo loci. Furthermore, phylogenetic analysis of the AhMlo loci along with homologs from other species has clustered the AhMlo loci into six clades. Three AhMlo loci were clustered in the clade V known to regroup the powdery susceptibility loci in dicots. Additionally, four core promoters were predicted on the promoter region of the specific AhMlo along with cis-regulatory elements related to PM susceptibility. These results provided strong evidence of the identification and distribution of the Mlo loci in the cultivated peanut genome and the identified specific AhMlo loci can be used for loss of susceptibility study.