Three-dimensional visualization of the internal plastid membrane network during runner bean chloroplast biogenesis: dynamic model of the tubular-lamellar transformation

Chloroplast biogenesis is a complex process integrated with plant development, leading to fully differentiated and functionally mature plastids. In this paper, the process of structural membrane transformation during the etioplast - chloroplast transition is reconstructed with the help of electron tomography and confocal microscopy. 3D reconstruction is the only method that leads to an understanding of the transformation of the regular, tubular network of paracrystalline prolamellar bodies (PLB) and prothylakoids (PT), flattened porous membranes, to the chloroplast thylakoids. We provide spatial models of the bean chloroplast biogenesis that allow such reconstruction of the internal membranes of the developing chloroplast and visualize the transformation from the tubular arrangement to the linear system of parallel lamellae. We prove that the tubular structure of the PLB transforms directly to flat slats, without dispersion to vesicles. We demonstrate that the grana/stroma thylakoid con...