Genome-Wide Characterization of the Role of WRKY and VQ Gene Families in Pecan and Their Expression Profile During Development and in Response to Abiotic Stresses

Pecan is an important oilseed tree species valued for its nutrient-rich nuts. WRKY and VQ proteins play crucial roles in plant growth, development, and stress response. However, few WRKY and VQ genes in pecan have been functionally analyzed due to functional redundancy caused by gene duplication. In this study, 89 CiWRKYs and 47 CiVQs were identified in pecan genome, which were unevenly distributed across chromosomes. Gene structure and conserved motif analyses revealed high diversity among members. Duplication analysis indicated that segmental duplication was the major factor of family expansion of CiWRKY and CiVQ. Ka/Ks ratios revealed that most duplicated gene pairs underwent purifying selection. Promoter analysis identified numerous cis-acting elements associated with light response, hormone regulation, and abiotic stress, implying their potential regulatory roles in development and stress response. Expression data across six tissues demonstrated tissue-specific patterns, with several genes highly expressed in flowers and roots. Transcriptome analysis revealed that 63 CiWRKY and 27 CiVQ genes were significantly upregulated under drought stress. qRT-PCR validation confirmed that CiPaw.10G165200 and CiPaw.04G072500 were highly induced by salt treatment, with expression levels increasing over 100-fold at 8 d. Moreover, CiPaw.10G165200 was also highly expressed under ABA treatment, which indicated it might play a key role in the response to abiotic stresses. Our results provide valuable insights into the evolutionary patterns and functional roles of WRKY and VQ genes in pecan and lay a foundation for improving stress tolerance and molecular breeding in this economically important nut tree.