Genome-wide exploration and characterization of the RALFs and analysis of its role in peanut (Arachis hypogaea L.)

Rapid alkalinization factors (RALFs) are small peptides hormones that regulate plant growth and stress responses. Although RALFs have been identified in a broad range of land plant species, their roles in peanuts (Arachis hypogaea L.) remain largely unexplored.

A total of 24 AhRALF genes we identified in the peanut genome and classified them into three clades through phylogenetic analysis. Whole genome duplication (WGD) or segmental duplication primarily drives the expansion of AhRALFs. Gene transcription analysis revealed that two genes from clade II (AhRALF1 and AhRALF12) and three from clade III (AhRALF8, AhRALF10, and AhRALF21) are highly expressed across 18 different tissues. Notably, AhRALF11 and AhRALF24, paralogous genes from clade II, are specifically expressed in immature buds and flowers. Additionally, AhRALF1, AhRALF12, AhRALF8, and AhRALF21 exhibited elevated expression under aluminum (Al) stress. Functional analysis of AhRALF1 confirmed its secretory function and inhibitory effect on root growth in Arabidopsis. Moreover, AhRALF1-silenced plants displayed reduced tolerance to Al stress, with altered antioxidant enzyme activities and increased oxidative damage.

This study provides a comprehensive analysis of the AhRALF gene family in peanut, highlighting their roles in growth regulation and stress responses. The function of AhRALF1 in enhancing peanut tolerance to Al stress was preliminary revealed. Our findings provide valuable insights into the roles of AhRALFs in peanuts and lay the groundwork for future functional studies and breeding programs.