Candidate Gene Fragments Responsible for Programmed Cell Death in Zea mays Kernel Endosperm
Mentor:Stacey Darling-Novak, Professor of Biology, University of La Verne
During the development of maize kernels, endosperm tissue undergoes a process called programmed cell death (PCD). Although this is a normal part of kernel maturation, PCD may result in suboptimal starch yield for the kernel. However, delaying this event may provide time for increased grain fill. Elucidation of the gene-controlled pathways associated with endosperm PCD could provide insight into ways to modify this crucial developmental phase. Prior experiments revealed that kernels cultured in high sucrose showed accelerated PCD in the endosperm. This was evident from viability staining and the presence of internucleosomal DNA fragmentation. Test groups were cultured in high sucrose medium to accelerate PCD, and control groups were left on the ear for an equivalent time period. The differential expression of mRNA between these two groups indicated candidate genes for PCD. Using cDNA AFLP technology, 120 differentially expressed fragments were found. Of these fragments, six have been successfully sequenced and analyzed using an NCBI Blast. One of the genes showed high homology to a 5-methylcytosine glycosylase, which is responsible for the active demethylation pathway that can initiate gene expression. Other fragments showed homology to “Zea mays PCO068470 mRNA sequence,” “Zea mays pyruvate orthophosphate dikinase mRNA, partial cds,” and “Zea mays actin-depolymerizing factor 6.” The expression of these genes indicate they may influence PCD, and modification of their expression may allow for more efficient starch accumulation.