Comprehensive analysis of the cysteine-rich polycomb-like protein (CPP) gene family in peanut: insights into its...

Peanut (Arachis hypogaea) is a crucial industrial crop whose production is severely limited by drought and salt stress. The CPP (cysteine-rich polycomb-like protein) gene family encodes cysteine-rich transcription factors with CXC domains that are involved in plant development and stress responses in addition to transcriptional regulation. However, their functional characterization in peanut remains largely unexplored. Here, the CPP gene family in peanut was systematically identified using bioinformatics approaches, after which its structural and functional attributes were comprehensively characterized. In total, 24 CPP genes were identified in the peanut genome; these genes were unevenly distributed across 15 chromosomes, with a relatively high density observed on chromosomes 9 and 16. All paralogs showed Ka/Ks less than 1, indicating strong purifying selection and functional conservation. A comparison of synteny revealed widespread collinearity of AhCPP genes across monocots and dicots, with AhCPP5 and AhCPP18 maintaining synteny in five species, highlighting their evolutionary stability. An analysis of cis-regulatory elements in AhCPP genes revealed the enrichment of diverse regulatory motifs, suggesting their potential roles in hormone signaling and stress responses in peanut. In addition, 116 putative miRNAs targeting 24 AhCPP genes were identified. Moreover, the transcriptomic analysis further revealed that AhCPP genes exhibited tissue- and stress-specific expression profiles in response to diverse abiotic stresses and hormonal stimuli. qRT-PCR analysis of six selected AhCPP genes suggested their potential involvement in the transcriptional regulation of drought and salt stress responses during the peanut seedling stage. Taken together, these findings provide a foundation for future functional investigations of AhCPPs for peanut breeding.