Aphid-host plant interactions: Does aphid honeydew exactly reflect the host plant amino acid composition?

peer reviewedPlants provide aphids with unbalanced and low concentrations of amino acids. Likely, intracellular symbionts improve the aphid nutrition by participating to the synthesis of essential amino acids. To compare the aphid amino acid uptakes from the host plant and the aphids amino acid excretion into the honeydew, host plant exudates (phloem + xylem) from infested and uninfested Vicia faba L. plants were compared to the honeydew produced by two aphid species (Acyrthosiphon pisum Harris and Megoura viciae Buckton) feeding on V. faba. Our results show that an aphid infestation modifies the amino acid composition of the infested broad bean plant since the global concentration of amino acids significantly increased into the host plant in response to aphid infestations. Specifically, the concentrations of two amino acids glutamine and asparagine were strongly enhanced. The amino acid profiles from honeydews were similar for the two aphid species, but the concentrations found into the honeydews were generally lower than those measured in the exudates of infested plants (aphids uptakes). This work also highlights that aphids take large amounts of amino acids into the host plant, especially glutamine and asparagine which are converted into glutamic and aspartic acids but also into other essential amino acids. The amino acid profiles differed between the host plant exudates and the aphid excretion product. Finally, this study highlights that the pea aphid - a “specialist” for the V. faba host plant - induced more important modifications into the host plant amino acid composition than the “generalist” aphid M. viciae.Solaphi

Relações entre o teor de fenóis totais e o ciclo das galhas de Cecidomyiida e em Aspidosperm a spruceanum Müll. Arg. (Apocynaceae) Relationships between phenolic contents and a Cecidomyiidae gall cycle in Aspidosperma spruceanum Müll. Arg. (Apocynaceae)

Alterações morfológicas detectadas em diversas espécies vegetais em função da indução de galhas são comumente acompanhadas de mudanças químicas importantes para o estabelecimento e manutenção do sistema galhador-planta hospedeira. O estudo da variação do teor de fenóis totais e sua relação com o desenvolvimento das galhas no sistema Aspidosperma spruceanum-Cecidomyiidae foi realizado ao longo de um ano, no qual foram detectados pelo menos dois ciclos de vida dos insetos indutores. O nível de infestação foliar foi alto, atingindo 87%, e os Cecidomyiidae tiveram a região internervural como sítio preferencial de oviposição. A variação sazonal no conteúdo de fenóis totais nas amostras de folhas sadias e galhadas foi primariamente relacionada às condições abióticas e muito embora este teor tenha atingido o máximo de 10 mg EAT g-1, indicando um ambiente químico celular não favorável à indução e a sua sobrevivência, o indutor de A. spruceanum supera esta barreira química, podendo ainda ser favorecido pela proteção contra inimigos naturais propiciada pelos fenólicos.<br>Morphological alterations detected in several plant species due to gall induction are commonly followed by chemical changes fundamental to the establishment and maintenance of the host plant-gall maker system. The study of phenolic contents variation and its relation to gall development in Aspidosperma spruceanum-Cecidomyiidae system through a year-time detected two insect life cycles. The level of infestation was high, getting up to 87%, and the Cecidomyiidae preferentially oviposited in internervural region. Seasonal variation in phenolic contents in healthy and galled leaves detected in A. spruceanum was primarily related to abiotic conditions. Even though the levels of phenolic contents might get a maximum of 10 mg EAT g-1, which indicated a non stimulating cell chemical environment to gall induction and herbivore survivorship, A. spruceanum gall maker surpassed this chemical barrier, and might also be favored by the chemical protection against its natural enemies, that phenolic contents might confer

Comparative analysis of phenolic profiles of ovipositional fluid of Rhinusa pilosa (Mecinini, Curculionidae) and its host plant Linaria vulgaris (Plantaginaceae)

Rhinusa pilosa (Gyllenhal) is a highly specific weevil that induces stem galls on the common toadflax Linaria vulgaris Mill. females oviposit the eggs near the apex of a growing shoot. The act of oviposition is accompanied by secretion of an ovipositional fluid, which is considered to be cecidogen, directly involved in gall induction. The remains of cecidogenic fluid were collected from the surface of the oviposition point on the stem. We performed a comparative analysis of the phenolics extracted from cecidogen, the stem and galls of L. vulgaris and adult and larva of R. pilosa by HPLC-DAD. One compound with A (max) at 273, 332 nm (R (t) 30.65 min) was exclusively found in the methanol extract of cecidogen. To further characterize the cecidogen and stem phenolic profiles, we used UHPLC coupled with an OrbiTrap mass analyzer. Among 49 phenolic compounds extracted from both the ovipositional fluid and the plant, protocatechuic acid and two phenolic glycosides were exclusively found in cecidogen: diosmetin-O-acetylrutinoside and an unidentified compound. The unknown compound produced an MS2 base peak at 387 and 327 and 267 m/z base peaks at MS3 and MS4 fragmentation, respectively, and had the molecular formula C32H31O18. The plausible role of phenolic compounds in the induction of gall formation on L. vulgaris is discussed