Effect of ethylene on polygalacturonase, lipoxygenase and expansin in ripening of tomato fruits

Abstract

Fruit ripening is a complex process and is regulated by many factors. Ethylene and polygalacturonase (PG), lipoxygenase(LOX), expansin(EXP) are all critical regulating factors in fruit ripening and softening process. With antisense ACS tomato, Nr mutant tomato and cultivated tomato as materials, Northern blot hybridization showed that PG, LeEXP1 and LOX expressed differently in different parts of cultivated tomato fruit during ripening, which was related to fruit ripening. The ripening process of columella and radial pericarp was faster than pericarp. In both Nr mutant and antisense ACS transgenic tomato fruit, expression levels of PG, LeEXP1 and LOX were generally lower than those in cultivated fruit but still related to fruit ripening. The expression levels of PG, LeEXP1 and LOX increased in the mature green tomato fruits after 0.5 h treatment with ethylene (100 μL/L). These results indicate that gene expression of PG, LeEXP1 and LOX were positively regulated by ethylene. The time and cumulative effect of the concentration exists in the expression of PG regulated by ethylene. The regulation of LOX expression mainly depended on the fruit development after great amount of ethylene was produced. PG played a major role in ripening and softening of tomato fruit, and cooperated with the regulation of EXP and LOX.