Anaerobic treatment dramatically alters the pattern of gene expression in maize (zea mays L.) seedlings. During anaerobiosis there is an immediate repression of pre-existing protein synthesis and the simultaneous selective synthesis of four polypeptides with a molecular weight of ˜33 kDa (the transition polypeptides). After 90 min, this is followed by specific transcription and mRNA accumulation as well as the selective synthesis of approximately 20 anaerobically-induced proteins. Among these anaerobic proteins (ANPs) are enzymes involved in glycolysis and related processes, such as alcohol dehydrogenase (ADH) aldolase, enolase, glucose-phosphate isomerase, glyceraldehyde-3-phosphate dehydrogenase, pyruvate decarboxylase, and sucrose synthase. However, two genes, inducible by oxygen deprivation, have been found that have different functions. One that has homology to xyloglucan endotransglycosylase may be involved in aerenchyma formation during flooding. The anaerobic response is most likely a plant's natural reaction to flooding. A similar condition has been observed in every plant species analysed to date. The anaerobic response and flooding tolerance in maize has been analysed using a combination of molecular, biochemical and genetic approaches. The studies include the characterization of anaerobically inducible genes, the identification of genes involved in flooding tolerance, and analysis of the signal transduction events that are involved in the perception of oxygen deprivation and lead to the anaerobic response.