MYB transcription factors (TFs) comprise a large gene family that plays an important role in plant growth, development, stress responses, and defense regulation. However, their functions in peanut remain to be further elucidated. Here, we identified six AhMYB44 genes (AhMYB44-01/11, AhMYB44-05/15, and AhMYB44-06/16) in cultivated peanut. They are typical R2R3-MYB TFs and have many similarities but different expression patterns in response to drought stress, suggesting different functions under drought stress. Homologous genes with higher expression in each pair were selected for further study. All of them were nuclear proteins and had no self-transactivation activity. In addition, we compared the performances of different lines at germination, seedling, and adult stages under drought stress. After drought treatment, the overexpression of AhMYB44-11 transgenic plants resulted in the longest root length at the seedling stage. Levels of proline, soluble sugar and chlorophyll, and expression levels of stress-related genes, including P5CS1, RD29A, CBF1, and COR15A, were higher than those of the wild type (WT) at the adult stage. While the overexpression of AhMYB44-16 significantly increased the drought sensitivity of plants at all stages, with differential ABA content, the expression levels of the ABA-related genes PP2CA and ABI1 were significantly upregulated and those of ABA1 and ABA2 were significantly downregulated compared with the WT. AhMYB44-05 showed similar downregulated expression as AhMYB44-16 under drought stress, but its overexpression in Arabidopsis did not significantly affect the drought resistance of transgenic plants. Based on the results, we propose that AhMYB44-11 plays a role as a positive factor in drought tolerance by increasing the transcription abundance of stress-related genes and the accumulation of osmolytes, while AhMYB44-16 negatively regulates drought tolerance through its involvement in ABA-dependent stress response pathways.

To investigate the potential role of phytochrome (PHY) in peanut growth and its response to environmental fluctuations, eight candidate AhPHY genes were identified via genome-wide analysis of cultivated peanut. These AhPHY polypeptides were determined to possess acidic and hydrophilic physiochemical properties and exhibit subcellular localization patterns consistent with residence in the nucleus and cytoplasm. Phylogenetic analysis revealed that the AhPHY gene family members were classified into three subgroups homologous to the PHYA/B/E progenitors of Arabidopsis. AhPHY genes within the same clade largely displayed analogous gene structure, conserved motifs, and phosphorylation sites. AhPHY exhibited symmetrical distribution across peanut chromosomes, with 7 intraspecific syntenic gene pairs in peanut, as well as 4 and 20 interspecific PHY syntenic gene pairs in Arabidopsis and soybean, respectively. A total of 42 cis-elements were predicted in AhPHY promoters, including elements implicated in phytohormone regulation, stress induction, physiology, and photoresponse, suggesting putative fundamental roles across diverse biological processes. Moreover, spatiotemporal transcript profiling of AhPHY genes in various peanut tissues revealed distinct expression patterns for each member, alluding to putative functional specialization. This study contributes novel insights into the classification, structure, molecular evolution, and expression profiles of the peanut phytochrome gene family, and also provides phototransduction gene resources for further mechanistic characterization.

Drought is a significantly environmental factor that poses a serious threat to peanut yield and quality in China. Our study aims to elucidate the regulatory mechanism of the drought stress response gene AhMYB44-11 and uncover the function of its promoter. We isolated the promoter sequence AhMYB44-11-Pro from the peanut genome and constructed recombinant expression vectors comprising the full-length promoter and several 5'-terminal deletion promoters, each fused with the GUS reporter gene. These vectors were then introduced into plant tissue via Agrobacterium rhizogenes-mediated transformation to assess promoter activity and expression patterns. The results revealed that AhMYB44-11-Pro contains a higher number of drought-responsive cis-regulatory elements, including MBS and Myb-binding sites, compared to the promoter of its homologous gene AhMYB44-01. Furthermore, dehydration treatment significantly enhanced GUS staining and activity in AhMYB44-11-Pro transgenic Arabidopsis, indicating that the promoter’s activity is upregulated under drought stress. These findings confirm that AhMYB44-11-Pro functions as a drought-inducible promoter. Additionally, AhMYB44-11-Pro contains a seed endosperm-specific expression element and gibberellin response elements, demonstrating an increased expression trend during pod development, as evidenced by GUS histochemical staining. This suggests that AhMYB44-11 may play a crucial role in seed development, particularly in dry matter accumulation. This research lays the groundwork for a comprehensive analysis of the biological functions of AhMYB44 and provides a valuable reference for genetically enhancing crop drought resistance.