Fig. 2: Restoration of male fertility by paternal mitochondrial inheritance.

a, Growth and developmental phenotypes of WT and PMt plants cultivated in the greenhouse. Images were captured at 55 days (top) and 75 days (middle) after sowing. Bottom: close-up views of floral morphology in WT, PMt-3, -4 and -5 plants. PMt-3 displayed a Δnad9-like mutant phenotype, including rolled-up leaf margins, impaired flower development with curly corolla margins and vestigial anthers lacking pollen. By contrast, PMt-4 resembled the WT plant in leaf and floral morphology, and exhibited WT-like pollen production. PMt-5 exhibited signs of heterochondriomy, indicated by a mixture of Δnad9-like (arrowheads) and WT-like leaves (arrows) at early stages (top). However, as the plant continued to grow, later-emerging leaves no longer exhibited the Δnad9 phenotype (middle), and all flowers appeared WT-like with normal pollen production (bottom). Scale bars, 2 cm. b, Confocal microscopy images of pollen from WT, PMt-3 and -4 plants. Pollen viability was assessed using FDA and PI staining. Both WT and PMt-4 plants produce viable pollen, indicated by FDA-derived green fluorescence observed in pollen grains. By contrast, PMt-3 pollen was non-viable, exhibiting only PI fluorescence due to the absence of cytoplasmic esterase activity required for FDA–fluorescein conversion and increased permeability to PI. Scale bars, 50 μm. The pollen viability assay was performed twice per plant and representative images are shown. c, Representative seed capsules that originated from self-pollinated WT and PMt-4 flowers. Except for PMt-3, all PMt plants produced WT-like seed capsules and exhibited normal seed yields. Scale bars, 1 cm.