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.