Genome-wide identification of the PIF gene family in blueberry reveals VcPIF7 as a far red light-induced repressor of fruit ripening.

Abstract

Phytochrome-interacting factors (PIFs) are a family of basic helix-loop-helix (bHLH) transcription factors that serve as central integrators of light signaling and developmental programs. Although PIFs have been well characterized in model species, their genome-wide landscape in blueberry (Vaccinium duclouxii) and the mechanisms by which they regulate fruit ripening have not been fully explored. Here, systematic analysis of the V. duclouxii genome identified eight VcPIF genes, which were comprehensively characterized with respect to their physicochemical properties, evolutionary relationships, gene structures, conserved motif compositions, and cis-elements. Expression profiling revealed that several VcPIF genes are highly expressed during fruit ripening and display diverse transcriptional responses to different light qualities. Notably, VcPIF7 emerged as a highly light-sensitive regulator, being sharply repressed by red (R) light and markedly induced by far-red (FR) light. Functional assays demonstrated that VcPIF7 negatively modulates fruit ripening by maintaining fruit firmness, inhibiting the accumulation of anthocyanins and soluble solids, and sustaining elevated total acid content. Subcellular localization and dual-luciferase assays further established that VcPIF7 is a nuclear-localized transcriptional repressor that directly suppresses the promoter activities of VcCHS and VcF3H. These findings identify VcPIF7 as a FR light-induced repressor of blueberry fruit ripening, offering valuable genetic targets and mechanistic insights for the light-regulated improvement of blueberry fruit quality.