The Role and Regulation of Ethylene in the Cell Death Program of Maize Endosperm

University Of California-Riverside, Riverside CA

Investigators

Abstract

In cereal seeds, the starchy endosperm develops as a storage tissue that is fated to die prior to maturation but persists into the mature seed. The progression of cell death in the endosperm of developing maize kernels occurs in a highly organized manner which is accompanied by a moderate increase in nuclease activity and internucleosomal fragmentation on the nuclear DNA. The endosperm cell death program of wheat and maize is regulated, in part, by ethylene. Consequently, the analysis of the genes responsible for the biosynthesis and perception of ethylene, as well as the nuclease responsible for DNA fragmentation will extend our understanding of the regulation of the cell death program in cereal endosperm. The specific aims of this project are: (1) to investigate the expression of the ethylene biosynthetic and perception machinery during maize organ development and identify the endosperm-specific members of each gene family; (2) to determine the spatial and temporal regulation of the ethylene biosynthetic and perception machinery during the initiation and progression of the cell death program during endosperm development; (3) to isolate ACC synthase and ethylene receptor knock out mutants to genetically characterize the requirement for ethylene biosynthesis and perception for endosperm cell death; and (4) to characterize an endosperm-expressed nuclease and investigate its role in directing internucleosomal DNA fragmentation. The expression studies will be carried out using RT-PCR and in situ RNA localization throughout the development of the maize endosperm. Transposon-insertion mutagenesis has been used to generate mutants affecting ethylene biosynthesis which will be used for phenotypic analysis of ethylene during maize development. The proposed experiments will represent a significant advancement in understanding a basic yet poorly understood aspect of cereal kernel development that will contribute to the improvement of cereal crops by providing a novel means to increase yield through extending the window of storage reserve deposition during cereal seed development.