Ethanol production and mitochondrial-related gene expression of maize (Zea mays) seed during storage

Abstract

Mitochondrial degradation plays a vital role in seed deterioration. Novel markers were investigated based on a new method for quantifying maize seed deterioration during 12 months’ storage under ambient (lab bench, ~27°C and 50–80% relative humidity (RH)) or controlled ((15±1)°C and (50±5)% RH in bags with low oxygen permeability) conditions involving two techniques: 1) fast ethanol assay and 2) quantitative RT-PCR (qPCR) with four mitochondrial-related genes in maize seed: alcohol dehydrogenase (ADH1), alternative oxidase (AOX1), cytochrome c oxidase (COXc), and ATPase. Ethanol production during imbibition and the expression of genes using the new method were compared to the results of two conventional methods: a germination test and an accelerated ageing test. The results showed that germination following ambient seed storage reduced significantly compared to the controlled conditions, especially at 9 months of storage. Ethanol production of maize seed measured by fast ethanol assay increased during storage. After 6 months, the mean (n=4) ethanol production from seed under ambient conditions was 400 µg L–1 which was higher than under the controlled conditions (240 µg L–1). Stored mRNA level of COXc and ATPase significantly decreased over time in ambient storage but were quite stable under the controlled conditions. Maize seed was also treated for artificial ageing at 42°C in 100% RH for 12, 24, and 48 h. At 24 h after treatment (HAT), maize seed produced significantly more headspace ethanol than at 12 HAT and more than the control (non-treated seed). The transcription level of ADH1 and ethanol production increased. The transcription level of COXc was directly related to the severity of the ageing treatment. In conclusion, a combination of fast ethanol assay and qPCR enhanced understanding of maize seed deterioration and provided new possibilities for the evaluation of seed storability based on transcriptional levels.