Fig. 1: Autophagy is active in the integumentary tapetum during seed development.

a, b Analysis of proATG5:H2B-GFP (a) and proATG7:H2B-GFP (b) reporter lines revealed that both ATG5 and ATG7 are expressed in the integumentary tapetum. The cell wall was stained by SCRI Renaissance 2200 (SR2200), and the integumentary tapetum was delineated with dot lines. DAP, days after pollination; IT integumentary tapetum, n nucleus. Scale bars: 50 µm. c Autophagosomes in the integumentary tapetum were labeled by ATG8 immunofluorescence. The nuclei were co-stained with propidium iodide (PI). The lower row shows the magnified integumentary tapetal cells, which are outlined with the dot lines. Scale bars: 20 µm (upper row); 2.5 µm (lower row). d GFP-ATG8 was expressed in the integumentary tapetum driven by the tapetum-specific promoter NtTPE8. The integumentary tapetum and magnified integumentary tapetal cell were delineated with dot lines. Scale bars: 20 µm (upper row); 2.5 µm (lower row). e Transmission electron microscopy assays show typical autophagosomes and autophagic bodies in the integumentary tapetum. AU autophagosomes, AB autophagic bodies, V vacuole. Scale bars: 2 µm (left); 200 nm (right). Observation of GFP in proATG5:H2B-GFP (a) and proATG7:H2B-GFP (b), as well as the visualization of autophagosomes in the integumentary tapetum through ATG8 immunofluorescence (c), and the observation of GFP from the proTPE8:GFP-ATG8 (d) were repeated three times with similar results. The transmission electron microscopy experiment was performed two times with similar results.