Aphid saliva: a powerful recipe for modulating host resistance towards aphid clonal propagation

Abstract

The successful colonization of an aphid requires intimate/compatible association which is achieved in the susceptible host plant. During development of intimate association with the susceptible host plant, aphid explores ‘effector’ molecules enriched in saliva that translocate into the host cell to modulate host cell’s function (physiology) as well as structure for assuring the nutrient availability. ‘Effectors’ are saliva proteins and/or small molecules having ability to manipulate the host cell’s structure as well as function. These molecules are originated from an aphid saliva gland and move through the aphid stylet during interaction with the host plant. The compatibility between aphid and its susceptible host plant depends on successful effector molecules exchange for better access of nutrient from the host plant. The compatible interaction which is also known as intimate association promotes aphid’s growth and multiplication due to well access of host’s phloem sap. In resistant host plant, aphid saliva enriched with effector molecules are recognized by the host plant defense machinery resulting in inducing effective plant defense response that negatively impacts on aphid’s survival, growth, and multiplication. The interaction of saliva secreted effector molecules with the host defense machinery results in two extreme reactions—susceptible and resistance types. Genetic mutant study reveals that the salivary secreted effector molecules are required for sustained contact with the host plant and play pivotal role in establishing compatibility with the susceptible host plant. Recent findings are also quite indicative that the silencing of salivary effector gene in aphid reduces the sustained contact with the susceptible host plant resulting in reduced survival and multiplication in aphid. This knowledge of salivary gland secreted effector genes could be potentially explored in aphid control in agricultural as well as horticultural crops as a novel strategy for next generation aphid control to bypass the heavy use of insecticide which causes imbalance in ecology.