Author
 |
Booker, Fitzgerald |
|
Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/30/2003 Publication Date: 6/16/2003 Citation: Booker, F.L. 2004. Influence of ozone on ribonuclease activity in wheat (Triticum aestivum) leaves. Physiologia Plantarum 120:249-255. Interpretive Summary: Air pollutant ozone often accelerates aging in many plants, but the biochemical pathways involved in these responses remain unclear. However, these pathways need to be defined in order to understand how the deleterious effects of ozone on plant growth and yield manifest themselves, and to provide the basis for designing genetic approaches for mitigating plant damage from ozone. The objective of this study was to determine whether an enzyme involved in plant death, ribonuclease (RNase), was stimulated in soybean and wheat leaves following treatment with ozone. Results indicated that RNase activities were stimulated by ozone exposure in soybean and wheat leaves, which generally coincided with foliar injury from ozone. RNase activity assays indicated the presence of three major RNases in soybean and wheat leaves, and the expression of one or two was enhanced by the ozone treatment. One of the ozone- stimulated wheat RNases also was stimulated in naturally yellowing leaf tissues. Thus, pathological responses invoked by ozone stimulated specific RNase enzymes, at least one of which was observed in naturally yellowing wheat leaves. Identification of a specific RNases involved in ozone-induced early aging provides a target for manipulating gene expression that might suppress ozone- accelerated aging and thus promote yield. Technical Abstract: Air pollutant ozone often induces accelerated senescence in many plants, but the biochemical mechanisms involved in this response remain unclear. The objective of this study was to determine whether an enzyme involved in plant senescence, ribonuclease (RNase), was stimulated in soybean and wheat leaves following treatment with chronic ozone. Soybean plants were treated in open-top field chambers with either charcoal-filtered (CF) air or CF air plus ozone. Wheat plants were treated with either CF air or nonfiltered air plus ozone. Twelve-hour average ozone concentrations in the CF and ozone treatments were 29 and 74 to 90 ppb, respectively. Results indicated that RNase activities were stimulated by ozone exposure in soybean and wheat leaves, which generally coincided with foliar injury from ozone. RNase activity gels indicated the presence of three major RNase isozymes in soybean and wheat leaf extracts, and the expression of one or two isozymes was enhanced by the ozone treatment, depending on the species. One of the ozone-stimulated wheat isozymes also was stimulated in naturally senescent leaf tissues from plants in the CF treatment. Thus, senescence-like pathological responses invoked by ozone stimulated specific RNase isozymes, at least one of which was observed in naturally senescent wheat leaves. Increased RNase isozyme activity in response to ozone provides additional evidence that chronic ozone exposure stimulates enzymes and presumably genes similar to those involved in natural senescence. |
