Baculovirus‐induced tree‐top disease: how extended is the role of egt as a gene for the extended phenotype?. Issue 1 (31st December 2014)

• Record Type: Journal Article
• Authors: Ros, Vera I. D.; van Houte, Stineke; Hemerik, Lia; van Oers, Monique M.
• Is Part Of: Molecular ecology. Volume 24:Issue 1(2015)
• Page Start: 249
• Page End: 258
• Publication Date: 2014-12-31
• Subjects: Molecular ecology -- Periodicals; Molecular population biology -- Periodicals; 576
• DOI: 10.1111/mec.13019
• Languages: English
• ISSNs: 0962-1083

Abstract

<abstract abstract-type="main" id="mec13019-abs-0001"> <title>Abstract</title> <p>Many parasites alter host behaviour to enhance their chance of transmission. Recently, the ecdysteroid UDP‐glucosyl transferase (<italic>egt</italic>) gene from the baculovirus <italic>Lymantria dispar</italic> multiple nucleopolyhedrovirus (LdMNPV) was identified to induce tree‐top disease in <italic>L. dispar</italic> larvae. Infected gypsy moth larvae died at elevated positions (hence the term tree‐top disease), which is thought to promote dissemination of the virus to lower foliage. It is, however, unknown whether <italic>egt</italic> has a conserved role among baculoviruses in inducing tree‐top disease. Here, we studied tree‐top disease induced by the baculovirus <italic>Autographa californica</italic> multiple nucleopolyhedrovirus (AcMNPV) in two different host insects, <italic>Trichoplusia ni</italic> and <italic>Spodoptera exigua</italic>, and we investigated the role of the viral <italic>egt</italic> gene therein. AcMNPV induced tree‐top disease in both <italic>T. ni</italic> and <italic>S. exigua</italic> larvae, although in <italic>S. exigua</italic> a moulting‐dependent effect was seen. Those <italic>S. exigua</italic> larvae undergoing a larval moult during the infection process died at elevated positions, while larvae that did not moult after infection died at low positions. For both <italic>T. ni</italic> and <italic>S. exigua</italic>, infection with a mutant AcMNPV lacking <italic>egt</italic> did not change the position where the larvae died. We conclude that <italic>egt</italic> has no highly conserved role in inducing tree‐top disease in lepidopteran larvae. The conclusion that <italic>egt</italic> is a 'gene for an extended phenotype' is therefore not generally applicable for all baculovirus–host interactions. We hypothesize that in some baculovirus–host systems (including LdMNPV in <italic>L. dispar</italic>), an effect of <italic>egt</italic> on tree‐top disease can be observed through indirect effects of <italic>egt</italic> on moulting‐related climbing behaviour.</p> </abstract>