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Venomous protease of aphid soldier for colony defense.

ABSTRACT: In social aphids, morphological, behavioral, and physiological differences between soldiers and normal insects are attributed to differences in gene expression between them, because they are clonal offspring parthenogenetically produced by the same mothers. By using cDNA subtraction, we identified a soldier-specific cysteine protease of the family cathepsin B in a social aphid, Tuberaphis styraci, with a second-instar soldier caste. The cathepsin B gene was specifically expressed in soldiers and first-instar nymphs destined to be soldiers. The cathepsin B protein was preferentially produced in soldiers and showed a protease activity typical of cathepsin B. The cathepsin B mRNA and protein were localized in the midgut of soldiers. For colony defense, soldiers attack enemies with their stylet, which causes paralysis and death of the victims. Notably, after soldiers attacked moth larvae, the cathepsin B protein was detected from the paralyzed larvae. Injection of purified recombinant cathepsin B protein certainly killed the recipient moth larvae. From these results, we concluded that the cathepsin B protein is a major component of the aphid venom produced by soldiers of T. styraci. Soldier-specific expression of the cathepsin B gene was found in other social aphids of the genus Tuberaphis. The soldier-specific cathepsin B gene showed an accelerated molecular evolution probably caused by the action of positive selection, which had been also known from venomous proteins of other animals.

SUBMITTER: Kutsukake M

PROVIDER: S-EPMC509204 | biostudies-literature | 2004 Aug

REPOSITORIES: biostudies-literature

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Venomous protease of aphid soldier for colony defense.

Kutsukake Mayako M Shibao Harunobu H Nikoh Naruo N Morioka Mizue M Tamura Tomohiro T Hoshino Tamotsu T Ohgiya Satoru S Fukatsu Takema T

Proceedings of the National Academy of Sciences of the United States of America 20040726 31

In social aphids, morphological, behavioral, and physiological differences between soldiers and normal insects are attributed to differences in gene expression between them, because they are clonal offspring parthenogenetically produced by the same mothers. By using cDNA subtraction, we identified a soldier-specific cysteine protease of the family cathepsin B in a social aphid, Tuberaphis styraci, with a second-instar soldier caste. The cathepsin B gene was specifically expressed in soldiers and ...[more]

PMID: 15277678

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Project description:A pair of nearly isogenic tomato (Solanum lycopersicum) lines were used. These are: Motelle (Mi/Mi), root-knot nematode resistant and Moneymaker (mi/mi) root-knot nematode susceptible. A potato aphid (red biotype), imported from France, was used for infestation. An equal volume of sterile 1% carboxymethyl cellulose in water was added to the cleaned nematodes to keep them in suspension. The inoculum, consisting of 75-100 J2s, was dispensed in 10 µl aliquots using a repeat pipetter. The inoculum was pipetted 2 mm beneath the root tips. Control seedlings were inoculated with 0.5% carboxymethyl cellulose. After the desired incubation time (24 h or 36 h), seedlings were taken out of the boxes and a few set aside to check nematode infection rate. In our hand, this system results in 50% infection rate. The rest of the seedlings were placed on a water-saturated filter paper and the roots aligned. About 1 cm of the infected root tip was excised with a blade and quickly frozen on a polycarbonate membrane-lined 50 mm diameter Petri dish floating on liquid nitrogen and stored at -80C. Plants were grown for 6 weeks in a growth chamber under 16 h light/8 h dark at 25C in UCMix/sand, irrigated with water or MiracleGroR solution, then moved to an insect growth room (25C) 4-6 days before aphid infestation. Individual tomato leaflets were infested with 30-40 mixed stages of the potato aphids using plastic leaf cages. Four leaflets and two plants of each genotype were infested. Two plants of each genotype were used as controls. After the desired infestation time (6, 12, 24 or 48 h), leaflets were excised from the plants with a blade and sprayed with 1% SDS to force aphids to remove their stylets from the leaf tissue. Aphids were carefully removed from the leaflets and quickly frozen in liquid nitrogen. Control leaflets were excised and sprayed with 1% SDS before freezing. Samples were stored at -80C. RNA was isolated using the hot phenol method. Keywords: Direct comparison

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Venomous protease of aphid soldier for colony defense.

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Venomous protease of aphid soldier for colony defense.

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