Endosperm development in grasses has several distinct phases: early development, comprising double fertilization, syncytium formation, and cellularization; differentiation, which includes the formation of the main cell types (transfer cells, aleurone, starchy endosperm, and embryo-surrounding cells), the periods of mitosis and endoreduplication, and the accumulation of storage compounds; and maturation, which includes programmed cell death, dormancy, and desiccation. Mutant analysis has provided knowledge regarding genes that influence the differentiation and maturation phases of endosperm development, but much less is known about early development and its consequences. Studies in maize and wheat suggest the extent of cell division during early development plays an important role in grain yield, but little is known about its genetic basis. While it is difficult to study early endosperm development in most cereals, this is easier with maize, because the embryo sac can be isolated and the endosperm cultured in vitro. This project seeks to develop a novel method to investigate early development in maize endosperm by microinjecting nucleic acids into 2-3 days after pollination (DAP) embryo sacs. This approach has advantages for transforming endosperm because it does not require the time and labor-intensive procedures associated with current methods of producing transgenic maize plants. There are risks associated with these experiments, but if successful could be transformative for identifying the genetic mechanisms that regulate early endosperm development and the results, which can be accessed at http://ag.arizona.edu/research/larkinslab/index.htm, could have valuable practical applications.
