Heme oxygenase-1 is involved in the protection against chilling exerted by low ALA

BALESTRASSE KB; TOMARO ML; BATLLE A; NORIEGA GO

PHYTOCHEMISTRY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2010 vol. 71 p. 2038 - 2045

0031-9422

In this study, the possibility of enhancing chilling stress tolerance of soybean plants (Glycine max L.) by exogenous application of 5-aminolevulinic acid (ALA) was investigated. To improve chilling tolerance, ALA was applied in the Hoagland solution at various concentrations ranging from 0 to 40 ìM for 12 h. After ALA treatment, the plants were subjected to chilling stress at 4°C for 48 h. ALA at low concentrations (5-10 ìM) provided significant protection against chilling stress compared to non-ALAtreated plants, enhancing chlorophyll content (Chl) as well as relative water content (RWC). Increase of TBARS levels was also prevented, whereas exposure to higher ALA concentrations (15-40 ìM) brought about a dose depended  enhancement, reaching a maximum of 117% in plants pretreated with 40 ìM ALA compared to controls. ALA pre-treatment also elevated catalase (CAT) and heme oxygenase-1 (HO-1) activities. These findings indicate that HO-1 acts not only as the rate limiting enzyme in heme catabolism, but also as an antioxidant enzyme. The highest chilling tolerance was obtained with 5 ìM ALA pre-treatment. Results show that ALA, which is considered as an endogenous plant growth regulator, could be used effectively to protect soybean plants from the damaging effects of chilling stress by enhancing the activity of heme proteins, e.g., catalase (CAT) and by promoting heme catabolism leading to the production of the highly antioxidant biliverdin and carbon monoxide, without any adverse effect on the plant growth.