Cellular processes in the developing endosperm
The functional characterization of endosperm was found different from that of embryo as different number of modules presented a particular growth stage (Figures 3b, S5b). Modules DP1-DP8 were characterized as the stage of En-S1, including genes related to mitotic cell cycle, DNA replication, cell wall organization, mitochondrion, tricarboxylic acid cycle and starch biosynthetic process. En-S2 featured the overrepresentation of GO term nutrient reservoir activity and transporter activity in D9. Modules DP10-DP12 presented high expression of genes responsible for response to biotic stimulus (heat and water deprivation) and lipid storage, representing endosperm maturation at stage En-S3. Finally, the module DP13 presented an up-regulation of the genes involved in positive regulation of autophagy, organelle disassembly, metal ion transport, and cellular catabolic process, characteristic of the desiccation and dormancy stage of endosperm (En-S4). Notably, genes responsible for metal cluster binding, macromolecular complex, RNA processing and signal transducer activity were overrepresented in DP14-DP22 and were broadly expressed throughout development.