ABSTRACT
Pathogenesis-related protein-4 (PR-4) is generally believed to be involved in physiological processes. However, a comprehensive investigation of this protein in tung tree (Vernicia fordii) has yet to be conducted. In this study, we identified 30 PR-4 genes in the genomes of Euphorbiaceae species and investigated their domain organization, evolution, promoter cis-elements, expression profiles, and expression profiles in the tung tree. Sequence and structural analyses indicated that VF16136 and VF16135 in the tung tree could be classified as belonging to Class II and I, respectively. Phylogenetic and Ka/Ks analyses revealed that Hevea brasiliensis exhibited a significantly expanded number of PR-4 genes. Additionally, the analysis of promoter cis-elements suggested that two VfPR-4 genes may play a role in the response to hormones and biotic and abiotic stress of tung trees. Furthermore, the expression patterns of VfPR-4 genes and their responses to 6-BA, salicylic acid, and silver nitrate in inflorescence buds of tung trees were evaluated using qRT-PCR. Notably, the expression of two VfPR-4 genes was found to be particularly high in leaves and early stages of tung seeds. These results suggest that VF16136 and VF16135 may have significant roles in the development of leaves and seeds in tung trees. Furthermore, these genes were found to be responsive to 6-BA, salicylic acid, and silver nitrate in the development of inflorescence buds. This research provides valuable insights for future investigation into the functions of PR-4 genes in tung trees.
ABSTRACT
The basic helix-loop-helix (bHLH) transcription factor gene family is one of the largest gene families and is extensively involved in plant growth, development, biotic and abiotic stress responses. Tung tree (Vernicia fordii) is an economically important woody oil plant that produces tung oil rich in eleostearic acid. However, the characteristics of the bHLH gene family in the tung tree genome are still unclear. Hence, VfbHLHs were first searched at a genome-wide level, and their expression levels in various tissues or under low temperature were investigated systematically. In this study, we identified 104 VfbHLHs in the tung tree genome, and these genes were classified into 18 subfamilies according to bHLH domains. Ninety-eight VfbHLHs were mapped to but not evenly distributed on 11 pseudochromosomes. The domain sequences among VfbHLHs were highly conserved, and their conserved residues were also identified. To explore their expression, we performed gene expression profiling using RNA-Seq and RT-qPCR. We identified five, 18 and 28 VfbHLH genes in female flowers, male flowers and seeds, respectively. Furthermore, we found that eight genes (VfbHLH29, VfbHLH31, VfbHLH47, VfbHLH51, VfbHLH57, VfbHLH59, VfbHLH70, VfbHLH72) were significant differential expressed in roots, leaves and petioles under low temperature stress. This study lays the foundation for future studies on bHLH gene cloning, transgenes, and biological mechanisms.
