METABOLIC REGULATION OF THE MAIZE 22 KD ZEIN PROMOTER IN ENDOSPERM SLICES FROM YOUNG MAIZE KERNELS

Authors: Muhitch, Michael; LIANG, HUA - BRDC POST DOC

Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: It has previously been established that exogenous nitrogen stimulates zein gene expression in developing maize kernels. Here, we demonstrate that sugar also induces zein promoter-driven gene expression and examine the interaction between sugars and amino acids in this induction. Endosperm slices from young maize kernels (8 DAP) were pre-incubated for 24 hrs in MS salts with or without sugars prior to co-bombardment with 22 kD zein promoter/luciferase and ubiquitin-1/GUS constructs. After particle bombardment, slices were incubated in MS media containing various filter-sterilized sugar and amino acid supplements for 48 hrs before determination of reporter activities. When included in either the pre-incubation medium or in the post-bombardment medium, glucose or sucrose, but not mannitol, stimulated transient zein-driven luciferase, even in the absence of added nitrogen. Sugars appeared to mediate the stimulatory effects of added nitrogen, suggesting that C/N may directly influence zein gene expression. When the amino acid mixture was replaced with either glutamate or glutamine (at only 1/10th the concentration of the total amino acid mixture), both were effective in inducing luciferase activity. Higher concentrations of either glutamate or glutamine were, in fact, inhibitory.