Auxin response factors (ARFs) are transcription factors that regulate the transcription of auxin-responsive genes during plant growth and development. In this study, 29 and 30 ARF members were identified from the two wild peanut species, A. duranensis and A. ipaensis, respectively. The ARFs, including their classifications, conserved domains and evolutionary relationships were characterized. RNA-seq analyses revealed that some of the ARF genes were responsive to abiotic stress, particularly high salinity. In addition to abiotic stress, the expression of 2 ARF members was also regulated by biotic stress, specifically Bradyrhizobium infection in A. duranensis. The ARF gene Arahy.7DXUOK was predicted to be a potential target of miR160. Overexpression of miR160 could cause degradation of the Arahy.7DXUOK target gene transcript and increased salt tolerance in miR160OX transgenic plants. Therefore, these molecular characterization and expression profile analyses provide comprehensive information on ARF family members and will help to elucidate their functions to facilitate further research on peanuts.

The K⁺ transporter KT/HAK/KUP (K⁺ transporter/high-affinity K⁺/K⁺ uptake) family has a critical effect on K⁺ uptake and translocation in plants under different environmental conditions. However, the functional analysis of KT/HAK/KUP members in sweet potatoes is still limited. The present work reported the physiological activity of a new gene, IbHAK11, in the KT/HAK/KUP family in sweet potatoes. IbHAK11 expression increased significantly in the low K⁺-tolerant line compared with the low K⁺-sensitive line following treatment with low K⁺ concentrations. IbHAK11 upregulation promoted root growth in Arabidopsis under low K⁺ conditions. Under high saline stress, transgenic lines had superior growth and photosynthetic characteristics compared with the wild-type (WT). As for IbHAK11-overexpressing plants, activation of both the non-enzymatic and enzymatic reactive oxygen species (ROS) scavenging systems was observed. Therefore, IbHAK11-overexpressing plants had lower malondialdehyde (MDA) and ROS levels (including H₂O₂ and O²⁻) compared with WT under salt-induced stress. We also found that under both low K⁺ and high salinity conditions, overexpression of IbHAK11 enhanced K⁺ translocation from the root to the shoot and decreased Na⁺ absorption in Arabidopsis. Consequently, IbHAK11 positively regulated K⁺ deficiency and high salinity stresses by regulating K⁺ translocation and Na⁺ uptake, thus maintaining K⁺/Na⁺ homeostasis in plants.

Background: The cultivated peanut (Arachis hypogaea L., AABB) is an allotetraploid hybrid between two diploid peanuts, A. duranensis (AA genome) and A. ipaensis (BB genome). Miniature inverted-repeat transposable elements (MITEs), some of which are known as active nonautonomous DNA transposons with high copy numbers, play important roles in genome evolution and diversification. AhMITE1, a member of the MITE family of transposons, but information on the peanut genomes is still limited. Here, we analyzed AhMITE1, AuMITE1 and ApMITE1 in the cultivated (A. hypogaea) and two wild peanut (A. duranensis and A. ipaensis) genomes. Results: The cultivated and the two wild peanut genomes harbored 142, 14 and 21 AhMITE1, AuMITE1 and ApMITE1 family members, respectively. These three family members exhibited highly conserved TIR sequences, and insertions preferentially occurred within 2 kb upstream and downstream of gene-coding and AT-rich regions. Phylogenetic and pairwise nucleotide diversity analysis showed that AhMITE1 and ApMITE1 family members have undergone one round of amplification bursts during the evolution of the peanut genome. PCR analyses were performed in 23 peanut varieties and demonstrated that AhMITE1 is an active transposon and that hybridization or chemical mutagenesis can promote the mobilization of AhMITE1. Conclusions: AhMITE1, AuMITE1 and ApMITE1 family members were identified based on local BLAST search with MAK between the cultivated and the two wild peanut genomes. The phylogenetic, nucleotide diversity and variation copy numbers of AhMITE1, AuMITE1 and ApMITE1 members provides opportunities for investigating their roles during peanut evolution. These findings will contribute to knowledge on diversity of AhMITE1, provide information about the potential impact on the gene expression and promote the development of DNA markers in peanut.