Potato, Solanum Tuberosum, Defense Against Colorado Potato Beetle, Leptinotarsa Decemlineata (Say): Microarray Gene Expression Profiling of Potato by Colorado Potato Beetle Regurgitant Treatment of Wounded Leaves

Abstract

Colorado potato beetle (CPB) is a leading pest of solanaceous plants. Despite the economic importance of this pest, surprisingly few studies have been carried out to characterize its molecular interaction with the potato plant. In particular, little is known about the effect of CPB elicitors on gene expression associated with the plant's defense response. In order to discover putative CPB elicitor-responsive genes, the TIGR 11,421 EST Solanaceae microarray was used to identify genes that are differentially expressed in response to the addition of CPB regurgitant to wounded potato leaves. By applying a cutoff corresponding to an adjusted P-value of <0.01 and a fold change of >1.5 or <0.67, we found that 73 of these genes are induced by regurgitant treatment of wounded leaves when compared to wounding alone, whereas 54 genes are repressed by this treatment. This gene set likely includes regurgitant-responsive genes as well as wounding-responsive genes whose expression patterns are further enhanced by the presence of regurgitant. Real-time polymerase chain reaction was used to validate differential expression by regurgitant treatment for five of these genes. In general, genes that encoded proteins involved in secondary metabolism and stress were induced by regurgitant; genes associated with photosynthesis were repressed. One induced gene that encodes aromatic amino acid decarboxylase is responsible for synthesis of the precursor of 2-phenylethanol. This is significant because 2-phenylethanol is recognized by the CPB predator Perillus bioculatis. In addition, three of the 16 type 1 and type 2 proteinase inhibitor clones present on the potato microarray were repressed by application of CPB regurgitant to wounded leaves. Given that proteinase inhibitors are known to interfere with digestion of proteins in the insect midgut, repression of these proteinase inhibitors by CPB may inhibit this component of the plant's defense arsenal. These data suggest that beyond the wound response, CPB elicitors play a role in mediating the plant/insect interaction.

Aphid-deprivation from Brassica plants results in increased isothiocyanate release and parasitoid attraction

“…However, first indications emerging from recent work seem to contradict this view by demonstrating that insect herbivores might actively manipulate plant defence responses (Lawrence et al 2008;Pareja et al 2012;Schwartzberg et al 2011). Helicoverpa zea and Spodoptera exigua caterpillars' saliva contain glucose oxidases that reduce induced defences (Bede et al 2006;Musser et al 2002).…”

“…Helicoverpa zea and Spodoptera exigua caterpillars' saliva contain glucose oxidases that reduce induced defences (Bede et al 2006;Musser et al 2002). Attacks by Leptinotarsa decemlineata beetles suppress transcription of genes encoding for proteinase inhibitors also involved in plant defence (Lawrence et al 2008). The silverleaf whitefly Bemisia tabaci biotype B prevents the activation of the jasmonic acid-regulated defences by Arabidopsis plants, which decreases plant defences and enhances nymphal performance (Walling 2008;Zhang et al 2013).…”

Alteration of plant primary metabolism in response to insect herbivory

“…However, actual insect damage is not a prerequisite for reduced photosynthetic activity. Feeding by both chewing herbivores that remove leaf material (Reymond et al, 2004;Lawrence et al, 2008) and phloem-feeding insects that do not (Zhu-Salzman et al, 2004;Botha et al, 2006) resulted in lower levels of photosynthesis-related gene expression. Even plantperceived evidence of insect attack that does not lead to any actual damage (e.g.…”

Herbivore exploits orally secreted bacteria to suppress plant defenses

“…Previous research has shown that application of OSs from Colorado potato beetle (CPB; Leptinotarsa decemlineata) larvae to mechanically wounded plants suppressed induced defenses in tomato and potato compared with wounded and water-treated plants (16)(17)(18). To investigate potential mechanisms of defense suppression by CPB larvae, we asked if microbes in OSs from CPBs manipulate induced defenses.…”