Degree Type

Dissertation

Date of Award

2012

Degree Name

Doctor of Philosophy

Department

Genetics, Development and Cell Biology

First Advisor

Philip W. Becraft

Abstract

The outermost layer of the endosperm is a specific cell type called the aleurone which is one of the grain quality determining factors because of its high content in lipid, minerals and high quality proteins compared to starchy endosperm. The aleurone layer is also an attractive system to study cell fate determination because of the simplicity and plasticity of aleurone cell fate. Here we report the identification of naked endosperm (nkd) genes which are involved in aleurone differentiation in maize. The nkd mutant shows defects in aleurone cell identity and has approximately 3 outer cell layers instead of the single in WT. However these outer cells do not contain dense granular cytoplasm typical of normal aleurone and have sporadic expression of a Vp1 promoter GUS transgene, which is an aleurone identity marker. The nkd mutant phenotype shows 15:1 segregation ratio in F2 populations suggesting two recessive genes are involved in this phenotype. We performed map-based cloning and found two homologous genes in syntenic regions. The INDETERMINATE1 domain containing transcription factors ZmIDDveg9 and ZmIDD9 correspond to the nkd1 and nkd2 mutant genes on chromosomes 2 and 10, respectively. Independent Ds transposon insertion alleles of nkd1 and nkd2, nkd1-Ds and nkd2-Ds respectively, failed to complement the original nkd mutant. A Nkd2-RNAi line, in which both of nkd genes were knocked down, also showed the nkd mutant phenotype. The nkd transcripts were most abundant in developing kernels around 11 to16 days after pollination. The NKD proteins have putative nuclear localization signals as other IDD genes and GFP fusion proteins showed nuclear localization. The mutant phenotype and gene expression pattern suggest NKD functions in aleurone cell fate acquisition and differentiation.

Copyright Owner

Gibum Yi

Language

en

File Format

application/pdf

File Size

144 pages

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