Unexpected effects of chitinases on the peach-potato aphid (Myzus persicae Sulzer) when delivered via transgenic potato plants (Solanum tuberosum Linn�) and in vitro

Abstract

With the aim of producing insect-resistant potato plants, internode explants of Solanum tuberosum L. cv. Désirée were transformed with an Agrobacterium strain C58pMP90 containing an insect (Phaedon cochleariae: Coleoptera, Chrysomelidae) chitinase gene and the neomycin phosphotransferase (nptII) gene as selectable marker, both under the control of the viral CaMV 35S promoter. Three transformed potato lines (CH3, CH5 and CH25) exhibiting the highest chitinolytic activities were selected for feeding experiments with the peach-potato aphid, Myzus persicae (Sulzer), under controlled photoperiod and temperature conditions. Aphids fed on transgenic potato plants showed a reduced pre-reproductive period and an enhanced daily fecundity. Transgenic potato lines did not affect nymphal mortality, but improved several biological parameters related to aphid population's growth. Artificial diets were used to provide active (1, 10, 100 and 500 microg ml(-1)) and inactive (500 microg ml(-1)) bacterial (Serratia marcescens) chitinase to M. persicae. These compounds increased nymph survival at all active chitinase doses when compared to the control diet, while inactive chitinase did not. Although the pre-reproductive period was slightly shortened and the daily fecundity slightly higher, active and inactive chitinase provided as food led a reduction from 1 to 1.5 day population's doubling time. Therefore chitinase activity was responsible for the probiotic effects on aphids. Our results question the relevance of a chitinase-based strategy in the context of potato culture protection.

Purification and Characterisation of a 31-kDa Chitinase from the Myzus Persicae Aphid: A Target for Hemiptera Biocontrol

“…In a previous work, we reported the aphicidal effects (i.e. reduction of fecundity, increase of larval mortality, reduction of body size) of these two inhibitors [24]. Here, we confirm the direct and strong inhibition of M. persicae chitinase by allosamidin and psammaplin A, including at low concentrations (1 μg/mL).…”

“…Inhibition of purified chitinase M. persicae by allosamidin and psammaplin A was tested by incubating 5 μg of purified chitinase mixed with different concentrations of each inhibitor (1, 10 and 50 μg/mL) corresponding to the concentrations tested previously in aphids [24]. Residual chitinase activity was measured 1, 2 and 3 h after the addition of inhibitor as described in the previous section, using the colorimetric assay based on CM-Chitin-RBV hydrolysis.…”

“…Furthermore, an insect and a bacterial chitinase induced probiotic effects on the green peach potato aphid Myzus persicae Sulzer (Homoptera, Aphididae) when respectively expressed in transgenic potato plants or delivered in vitro via an artificial diet [23]. Due to the poor aphicidal effects of chitinase, the relevance of chitinase-based strategy was questioned to manage insects [24,25]. In contrast, two insect chitinase inhibitors, allosamidin [26] and psammaplin A [29], and an oligosaccharide that mimics allosamidin [5] have been shown to induce high mortality rates and reduce fecundity of M. persicae when fed with artificial diet [5,24].…”

“…Due to the poor aphicidal effects of chitinase, the relevance of chitinase-based strategy was questioned to manage insects [24,25]. In contrast, two insect chitinase inhibitors, allosamidin [26] and psammaplin A [29], and an oligosaccharide that mimics allosamidin [5] have been shown to induce high mortality rates and reduce fecundity of M. persicae when fed with artificial diet [5,24]. Among all insect chitinase proteins isolated from Lepidoptera [1,[16][17][18], Coleoptera [12,33] and Diptera [7,33,34], only 14 protein sequences are available [31].…”

Aphid resistance in potato

“…Экспрессирующийся в трансгенных растениях картофеля белок βглюкуронидаза повышал репродуктивную актив ность M. persicae, а один из трансформированных клонов был более предпочитаем тлей для заселения, чем исход ный сорт Désirée Cherqui et al, 2003). На трансформированных геном хитиназы жука Phaedon cochleariae растениях M. persicae развивалась быстрее, а плодовитость оказалась выше, чем при питании на ис ходном сорте Désirée (Saguez et al, 2005).…”