Submitted to: Maize Genetics Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/27/2008
Publication Date: N/A
Technical Abstract: In this study we explore maize kernel development with focus on sugar metabolism and starch production. Specifically, we use sugar metabolism mutants miniature1-1 (mn1-1, cell-wall-invertase deficient) and sugary1 (su1, starch-synthase deficient) to understand the possible significance of sugar signals related to levels of the phytohormone ethylene and expression profiles of ethylene-related genes. Our data combine transcriptional profiling of Hexokinase (HxK) and key ethylene biosynthesis and perception genes with direct hormone analysis to provide deeper understanding of the way ethylene action is influenced by the sugar status of the cell, and ultimately how this crosstalk modulates development. Wild-type Mn1 and Su1 maize kernels exhibit two peaks of ethylene, one ~14 days-after-pollination (DAP) and the second ~30 DAP. Preliminary data show that mn1-1 kernels (vs. Mn1) have slightly higher ethylene production during early development and peaks significantly earlier during final maturation. Despite ~70% reduced seed mass, mn1-1 produced comparable ethylene levels per kernel as Mn1. During early stages, HxK and the ethylene receptor Ethylene response 2 (ETR2-40) transcripts show pronounced differences from wild-type, while receptor Ethylene response sensor 1 (ERS1-14) begins to diverge at 16 DAP onward. ACC-synthase (ACS47) is variable throughout development, showing lower expression early in the mn1-1 line and peaks five days earlier (29 DAP), coinciding with rising ethylene production. For the starch-deficient sugary1 mutant, ethylene production peaks are phase-shifted four days earlier while retaining similar trends in amplitude. HXK and ERS1-14 show most difference during early development. ETR2-40 exhibits a similar trend in Su1 and su1 genotypes; however, the transcript is 2-3 fold more abundant in the mutant. ACS47 shows highest differences during early (8 DAP) and late (28 DAP) development. Overall, we observed altered levels of both ethylene hormone and related transcripts in developing seeds of two maize sugar mutants relative to the corresponding wild-types.