Transcriptomic and hormonic analyses reveal the effects of xenia on anthocyanin biosynthesis in blueberry

Xenia is the phenomenon whereby the pollen genotype directly affects seed and fruit development from fertilization to seed germination. Although anthocyanin accumulation in blueberry is influenced by xenia, the mechanism remains unknown. Considering the central role hormones in modulating fruit quality, we hypothesize that xenia alters endogenous hormone levels, affecting structural gene expression and thus anthocyanin accumulation. To validate this, 'Premier' blueberries were pollinated with different pollen genotypes; and parallel phenotypes assessed included anthocyanin content, hormone content and ratio, and integrated transcriptomic analyses. Results showed that anthocyanin rapidly accumulated 60 days after pollination (DAP), but significant differences between self- and cross-pollination emerged after 40 DAP. Self-pollination in 'Premier' resulted in significantly lower anthocyanin content than when cross-pollinated with 'Brightwell' and 'Powderblue' (P = 0.05). The hormone content and ratio significantly differed between self- and cross-pollination treatments (P = 0.05) during fruit development. Cross-pollination upregulated key structural genes, such as phenylalanine ammonia-lyase, chalcone synthase, flavanone 3-hydroxylase, and dihydroflavonol 4-reductase, but downregulated anthocyanidin reductase (FC > 2.00 and P < 0.01). The anthocyanin content was significantly related to the hormone content, hormone ratio, and expression levels of hub differentially expressed genes ('*', P = 0.05; '**', P = 0.01). These results confirm that xenia affects the differential expression of structural genes via hormones, influencing anthocyanin accumulation. These findings provide new insights into the mechanism by which xenia affects fruit quality and indicate that selecting appropriate pollen genotypes is a practical approach to improving the nutritional quality of fruit.