Fig. 1.

Schematic developmental progression of maize anthers and key mobile elements involved in the process. a Schematic cross sections or half-cross section of different anther developmental stages, ranging from before lobe specification, through mitotic proliferation to microgametogenesis. All anther cells date back to L1-d, L2-d cells and in dicots L3-d cells. L1-d become epidermis, while L2-d/L3-d cells form the vasculature, connective tissue and all lobe tissues. b Schematic timeline of anther lobe development. c Mobile elements known to occur during anther development. The approximate timing and levels of occurrence are depicted schematically by filled areas. Circles represent anther lobes, with gradients or layer-specific location shown by corresponding colors. Colors used are selected due to the colors in panel b, with mobile elements arising or occurring in the respective color-coded layers. AR: archesporial, EN: endothecium, EPI: epidermis, TP: tapetum