Salivary secretions by aphids interacting with proteins of phloem wound responses

• Published in: Journal of experimental botany 2006-03, Vol.57 (4), p.739-745
• Main Author: Tjallingii, W. Fred
• Format: Article
• Language: English
• Subjects: Animals; Aphidoidea; Aphids; Aphids - metabolism; Aphids - physiology; behavior; clogging; Electric Conductivity; Electric potential; electrical penetration graph; Entomology; Focus Papers: Phloem–Insect Interaction; insect pests; Insect stylets; literature reviews; penetration; pest resistance; Phloem; phloem protein; plant damage; plant pests; Plant Physiological Phenomena; Plant Proteins - metabolism; plant-insect relations; Plants; Plants - anatomy & histology; Plants - metabolism; Plants - parasitology; protein binding; resistance; resistance mechanisms; Saliva; Saliva - chemistry; Saliva - physiology; Saliva - secretion; Salivary glands; Salivation; Salivation - physiology; sap; Sieve elements; sieve tubes; tissue repair; Waveforms; wound response
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/erj088

Successful phloem feeding requires overcoming a number of phloem-related plant properties and reactions. The most important hurdle is formed by the phloem wound responses, such as coagulating proteins in the phloem sieve elements of the plant and in the capillary food canal in the insect's mouth parts, i.e. the stylets. It seems that in order to prevent protein clogging inside a sieve element, ejection of watery saliva plays an important role. This ejection is detected in the electrical penetration graph (EPG) as E1 salivation and always precedes phloem sap ingestion. During this feeding from sieve elements, another regular and concurrent salivation also occurs, the watery E2 salivation. This E2 saliva is added to the ingested sap and, it probably prevents phloem proteins from clogging inside the capillary food canal. Whatever the biochemical mode of action of the inhibition of protein coagulation might be, in some plants aphids do not seem to be able to prevent clogging, which may explain the resistance to aphids in these plants. The relevance of this hypothesis is demonstrated by new experimental results and is related to new EPG results from plants with phloem-located resistance.