Abstract
Plants employ different chemicals to protect themselves from herbivory. These defenses may be constitutive or triggered by stress. The chemicals can be toxic, act as repellents, phagosuppressants and/or phago-deterrents. The two-spotted spider mite (Tetranychus urticae) is a generalist arthropod herbivorous pest and its feeding causes extensive damage both to crops and wild plants. Cyclotides are cyclic peptides involved in host-plant defenses. A single Viola sp. can produce more than a hundred cyclotides with different biological activities and roles. The organ and tissue specific cyclotide patterns change over the seasons and/or with environment, but the role of biotic/abiotic stress in shaping them remains unclear. Here, we demonstrate the involvement of cyclotides in mutual interactions between violets and mites. We used immunohistochemistry and mass spectrometry imaging to show the ingested cyclotides in T. urticae and assess the Viola odorata response to mite feeding. Moreover, to assess how mites are affected by feeding on violets, acceptance and reproductive performance was compared between Viola uliginosa, V. odorata and Phaseolus vulgaris. We demonstrate that cyclotides had been taken in by mites feeding on the violets. The ingested peptides were found in contact with epithelial cells of the mite digestive system, in the fecal matter, feces, ovary and eggs. Mites preferred common bean plants (P. vulgaris) to any of the violet species; the latter affected their reproductive performance. The production of particular cyclotides in V. odorata (denoted by molecular weights: 2979, 3001, 3017, 3068, 3084, 3123) was activated by mite feeding and their levels were significantly elevated compared to the control after 5 and 21 days of infestation. Specific cyclotides may affect mites by being indigestible or through direct interaction with cells in the mite digestive tract and reproductive organs. A group of particular peptides in V. odorata appears to be involved in defense response against herbivores.
Highlights
Plants employ different chemicals to protect themselves from herbivory
Empty palisade and spongy mesophyll cells with collapsed and/or misshapen walls and enlarged intercellular spaces were clearly visible as evidence of mite feeding activity in mite-infested leaves of both V. odorata and V. uliginosa (Fig. 1a,b)
The current study provides a new insight into Viola–T. urticae mutual interactions and broaden the knowledge on the potential and biological roles of specific cyclotides produced by violets
Summary
Plants employ different chemicals to protect themselves from herbivory. These defenses may be constitutive or triggered by stress. The two-spotted spider mite (Tetranychus urticae) is a generalist arthropod herbivorous pest and its feeding causes extensive damage both to crops and wild plants. Cyclotides are cyclic peptides involved in host-plant defenses. We used immunohistochemistry and mass spectrometry imaging to show the ingested cyclotides in T. urticae and assess the Viola odorata response to mite feeding. To assess how mites are affected by feeding on violets, acceptance and reproductive performance was compared between Viola uliginosa, V. odorata and Phaseolus vulgaris. The two-spotted spider mite Tetranychus urticae Koch (Acariformes: Trombidiformes: Tetranychidae) is a cell-sucking arthropod pest with a worldwide distribution and as a generalist able to feed on a wide range of host-plants[9]. Besides the Violaceous family, in which the peptides seem to be produced by most species, cyclotides have been found in members of the Rubiaceae, Cucurbitaceae, Fabaceae, Solanaceae and Poaceae families[22,23,24,25,26,27,28]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
