摘要
Plants perceive and respond to environmental stresses with complex mechanisms that are often associ- ated with the activation of antioxidant defenses. A genetic screen aimed at isolating oxidative stress-tolerant lines of Arabidopsis thaliana has identified oxtl, a line that exhibits improved tolerance to oxidative stress and elevated temperature but displays no apparent deleterious growth effects under non-stress conditions. Oxtl harbors a muta- tion that arises from the altered expression of a gene encoding adenine phosphoribosyltransferase （APT1）, an enzyme that converts adenine to adenosine monophosphate （AMP）, indicating a link between purine metabolism, whole-plant growth responses, and stress acclimation. The oxtl mutation results in decreased APT1 expression that leads to reduced enzymatic activity. Correspondingly, oxtl plants possess elevated levels of adenine. Decreased APT enzyme activity dir- ectly correlates with stress resistance in transgenic lines that ectopically express APT1. The metabolic alteration in oxtl plants also alters the expression of several antioxidant defense genes and the response of these genes to oxidative chal- lenge. Finally, it is shown that manipulation of adenine levels can induce stress tolerance to wild-type plants. Collectively, these results show that alterations in cellular adenine levels can trigger stress tolerance and improve growth, leading to increases in plant biomass. The results also suggest that adenine might play a part in the signals that modulate responses to abiotic stress and plant growth.
Plants perceive and respond to environmental stresses with complex mechanisms that are often associ- ated with the activation of antioxidant defenses. A genetic screen aimed at isolating oxidative stress-tolerant lines of Arabidopsis thaliana has identified oxtl, a line that exhibits improved tolerance to oxidative stress and elevated temperature but displays no apparent deleterious growth effects under non-stress conditions. Oxtl harbors a muta- tion that arises from the altered expression of a gene encoding adenine phosphoribosyltransferase （APT1）, an enzyme that converts adenine to adenosine monophosphate （AMP）, indicating a link between purine metabolism, whole-plant growth responses, and stress acclimation. The oxtl mutation results in decreased APT1 expression that leads to reduced enzymatic activity. Correspondingly, oxtl plants possess elevated levels of adenine. Decreased APT enzyme activity dir- ectly correlates with stress resistance in transgenic lines that ectopically express APT1. The metabolic alteration in oxtl plants also alters the expression of several antioxidant defense genes and the response of these genes to oxidative chal- lenge. Finally, it is shown that manipulation of adenine levels can induce stress tolerance to wild-type plants. Collectively, these results show that alterations in cellular adenine levels can trigger stress tolerance and improve growth, leading to increases in plant biomass. The results also suggest that adenine might play a part in the signals that modulate responses to abiotic stress and plant growth.
