The senescence associated gene of barley encoding 4-hydroxyphenylpyruvate dioxygenase is expressed during oxidative stress

A cDNA containing the complete sequence of 4-hydroxyphenylpyruvate dioxygenase (HPPD) from barley is described. Compared to the HPPD sequence of non-plant organisms, the barley sequence and the other available HPPD amino acid sequences from plants possess an N-terminal extension and three insertions. Only a single copy of the hpd gene is present in the barley genome. The structure of the gene with one intron is the same as in Arabidopsis thaliana. It has been reported that barley leaves have an enhanced level of hpd gene-specific transcripts during senescence. In this paper we show that the transcript accumulates also after application of methyl jasmonate and ethylene to segments of barley leaves. Additionally, treatments of barley leaves with the herbicides paraquat and DCMU or with hydrogen peroxide stimulate expression of the hpd gene. Taken together, these results indicate that expression of the hpd gene during senescence most likely is related to oxidative stress.