Abstract
Drought is one of the major abiotic stresses affecting plant productivity. Under water deficit conditions, generation and proliferation of reactive oxygen species increases and results in oxidative damage to plant cells. In contrast to this idea established with domesticated or mild environment-adapted plants, wild watermelon, a C3-plant from the Kalahari desert, Botswana, had very unique mechanisms for surviving drought. Under stress conditions, the plants accumulated large amount of a novel compatible solute, citrulline, in the leaves. Citrulline is one of the most efficient hydroxyl radical-scavengers among natural compounds examined so far. Moreover, the plants induced unique set of proteins such as DRIP-1, metallothionein and cytochrome b-561 in response to drought. Some of these factors are thought to be involved in antioxidative defense system of the plants. Molecular analysis of drought-tolerant wild watermelon provides new hints and tools to improve the stress tolerance of crop plants.
