Ozone-Induced Accelerated Leaf SenescenceEPA Grant Number: U915212
Title: Ozone-Induced Accelerated Leaf Senescence
Investigators: Miller, Jennifer D.
Institution: Pennsylvania State University
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 1997 through January 1, 2000
Project Amount: $68,000
RFA: STAR Graduate Fellowships (1997) RFA Text | Recipients Lists
Research Category: Fellowship - Pathology , Academic Fellowships , Health Effects
The objectives of this research project are to determine: (1) if tropospheric ozone (O3) induces the early expression of senescence-associated genes (SAGs); and (2) the role of the hormone ethylene. O3 inflicts more damage on vegetation than any other air pollutant in the United States. Long-term exposures to low concentrations of O3 are known to accelerate foliar senescence, but the molecular components of this process remain unknown.
Arabidopis thaliana plants, ecotype Landsberg erecta, were grown in growth chambers at 24°C and 60 percent relative humidity under a 12 hour light/12 hour dark cycle at 180 mmol m-2 s-1. Transgenic plants carrying either the SAG12 or SAG13 promoter fused to the -glucuronidase (GUS) reporter gene also were grown. At approximately 2 1/2 weeks postemergence, half of the plants were treated with 150 ppb O3 for 6 hours per day for 8 or 14 days. Leaf tissue was harvested immediately after completion of the O3 treatment. RNA was extracted from leaves seven and eight (numbered by order of emergence from the meristem) pooled from six plants. Transcript levels of several SAGs and photosynthesis-associated genes (PAGs) were measured by northern analysis. GUS activity was measured in pooled rosette leaves seven and eight from transgenic plants. Leaves seven and eight from transgenic plants also were stained to visualize GUS activity.
The results of this research project will allow for more accurate predictions of the extent of damage caused by O3 stress. It may reveal that O3-induced senescence is a nuclear-controlled event. This information may be useful in reducing plant susceptibility to O3.