Cloning, phylogeny, and expression analysis of the Broad-Complex gene in the longicorn beetle Psacothea hilaris.

Keisuke Nagamine,Yukio Ishikawa,Tetsuro Shinoda,Sugihiko Hoshizaki,Takashi Matsuo,Takumi Kayukawa

doi:10.1186/2193-1801-3-539

Keisuke Nagamine, Yukio Ishikawa + Show 4 more

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https://doi.org/10.1186/2193-1801-3-539

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Abstract

Seven isoforms of Broad-Complex (PhBR-C), in which the sequence of the zinc finger domain differed (referred to as Z1, Z2, Z3, Z2/Z3, Z4, Z5/Z6, and Z6, respectively), were cloned from the yellow-spotted longicorn beetle Psacothea hilaris. The Z1–Z4 sequences were highly conserved among insect species. The Z5/Z6 isoform was aberrant in that it contained a premature stop codon. Z6 had previously only been detected in a hemimetabola, the German cockroach Blattella germanica. The presence of Z6 in P. hilaris, and not in other holometabolous model insects such as Drosophila melanogaster or Tribolium castaneum, suggests that Z6 was lost multiple times in holometabolous insects during the course of evolution. PhBR-C expression levels in the brain, salivary gland, and epidermis of larvae grown under different feeding regimens were subsequently investigated. PhBR-C expression levels increased in every tissue examined after the gut purge, and high expression levels were observed in prepupae. A low level of PhBR-C expression was continuously observed in the brain. An increase was noted in PhBR-C expression levels in the epidermis when 4th instar larvae were starved after 4 days of feeding, which induced precocious pupation. No significant changes were observed in expression levels in any tissues of larvae starved immediately after ecdysis into 4th instar, which did not grow and eventually died.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-539) contains supplementary material, which is available to authorized users.

Highlights

The yellow-spotted longicorn beetle Psacothea hilaris (Coleoptera: Cerambycidae) is an important pest of mulberry and fig trees in East Asia (Kusama and Takakuwa 1984), and has recently settled in Europe (Jucker et al 2006; Lupi et al 2013)
We previously reported that approximately 50% of 4th-instar P. hilaris larvae at 25°C and under a long-day photoperiod molted to the 5th instar on day 13 and pupated approximately 18 days thereafter; the remainder pupated without a larval molt with a mean 4th-instar period of 24 days (Shintani et al 1996)
PhBR-C cDNA Genomic DNA was prepared from the fat body of P. hilaris larvae

Summary

Introduction

The yellow-spotted longicorn beetle Psacothea hilaris (Coleoptera: Cerambycidae) is an important pest of mulberry and fig trees in East Asia (Kusama and Takakuwa 1984), and has recently settled in Europe (Jucker et al 2006; Lupi et al 2013). We have been interested in the developmental responses of P. hilaris larvae to starvation (Shintani et al 2003; Munyiri et al 2003, 2004; Munyiri and Ishikawa 2005a, b) because food shortages are a constraint that insects often have to contend with in nature. This beetle was shown to terminate its larval life precociously and form small pupae in response to the sudden exhaustion of a food supply (Shintani et al 2003). Hemolymph juvenile hormone (JH) levels and ecdysteroid titers in starved and normally fed larvae suggested that starvation induced a rapid decline in the JH titer, and this appeared to cue the early occurrence of a small ecdysteroid peak that committed larvae to metamorphosis (Munyiri and Ishikawa 2005a)

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