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Zinc finger-homeodomain (ZHD) proteins constitute a plant-specific transcription factor family that play important roles in plant growth, development, and stress responses. In this study, we investigated a total of 10, 17, and 31 ZHD gene members in the peach, Arabidopsis, and apple genome, respectively. The phylogenetic tree divided the identified ZHD genes into 4 subfamilies based on their domain organization, gene structure, and motif distribution with minor variations. The ZHD gene family members were unevenly distributed throughout in apple, peach, and Arabidopsis genomes. Segmental duplication was observed for 14 pairs of genes in apple. Transcript analysis found that ZHD genes mostly expressed in various tissues, particularly in leaves and flowers. Moreover, the transcript of most ZHD genes was significantly affected at different time points in response to various flowering-related exogenous hormones (sugar, gibberellin [GA], and 6-benzylaminopurine [6-BA]), signifying their possible role in the flowering induction in apple. Furthermore, the transcripts of CaZHD6, CaZHD7, CaZHD3, and CaZHD8 have induced in response to abiotic stresses including heat, drought, salt, and cold, indicating their possible involvement in response to abiotic stresses. Our research work systemically presents the different roles of ZHD genes. We believe that this study will provide a platform for future functional characterization of ZHD genes and to deeply unfold their roles in the regulation of flowering induction in plants. [ABSTRACT FROM AUTHOR]

Background: High-density genetic mapping is a valuable tool for mapping loci that control specific traits for perennial fruit trees. Peach is an economically important fruit tree and a model Rosaceae species for genomic and genetic research. In peach, even though many molecular markers, genetic maps and QTL mappings have been reported, further research on the improvement of marker numbers, map densities, QTL accuracy and candidate gene identification is still warranted. Results: A high-density single nucleotide polymorphism (SNP)-based peach linkage map was constructed using specific locus amplified fragment sequencing (SLAF-seq). This genetic map consisted of 7998 SLAF markers, spanning 1098.79 cM with an average distance of 0.17 cM between adjacent markers. A total of 40 QTLs and 885 annotated candidate genes were detected for 10 fruit-related traits, including fruit weight (FW), fruit diameter (FD), percentage of red skin colour (PSC), eating quality (EQ), fruit flavour (FV), red in flesh (RF), red around pit (RP), adherence to pit (AP), fruit development period (FDP) and fruit fibre content (FFC). Eighteen QTLs for soluble solid content (SSC) were identified along LGs 1, 4, 5, and 6 in 2015 and 2016, and 540 genes were annotated in QTL intervals. Thirty-two QTLs for fruit acidity content (FA) were detected on LG1, and 2, 4, 5, 6, and 1232 candidate genes were identified. The expression profiles of 2 candidate genes for SSC and 4 for FA were analysed in parents and their offspring. Conclusions: We constructed a high-density genetic map in peach based on SLAF-seq, which may contribute to the identification of important agronomic trait loci. Ninety QTLs for 12 fruit-related traits were identified, most of which overlapped with previous reports, and some new QTLs were obtained. A large number of candidate genes for fruit-related traits were screened and identified. These results may improve our understanding of the genetic control of fruit quality traits and provide useful information in marker-assisted selection for fruit quality in peach breeding programmes. [ABSTRACT FROM AUTHOR]