A unique latex protein, MLX56, defends mulberry trees from insects

Area of Science:

• Plant biology
• Entomology
• Biochemistry

Background:

• The interaction between mulberry (Morus spp.) and silkworms (Bombyx mori) is a long-standing plant-herbivore relationship.
• Mulberry leaves employ latex compounds for defense against insect damage.

Purpose of the Study:

• To identify and characterize a specific defense protein in mulberry latex responsible for insect resistance.
• To investigate the mechanism of action and specificity of this defense protein.

Main Methods:

• Isolation and identification of a 56-kDa protein (mulatexin, MLX56) from mulberry latex.
• Analysis of MLX56's protein domains (extensin, hevein-like chitin-binding, inactive chitinase-like).
• Testing MLX56 toxicity against lepidopteran caterpillars (Mamestra brassicae, Samia ricini) and Bombyx mori.

Main Results:

• MLX56 confers strong insect resistance to mulberry plants.
• MLX56 is toxic to Mamestra brassicae and Samia ricini at low concentrations (0.01%) but not to Bombyx mori.
• The protein is protease-resistant and exhibits strong chitin-binding activity.

Conclusions:

• Plant latex proteins, like MLX56, play a crucial role in plant-insect interactions.
• MLX56 is a promising candidate for developing natural pesticides for plant protection.
• Specialist herbivores, such as Bombyx mori, can evolve adaptations to overcome plant defense mechanisms.