Photoperiodic effects on diapause‐associated gene expression trajectories in European Leptinotarsa decemlineata populations

Abstract

Behavioural and physiological changes during diapause, an important strategy of insects for surviving harsh seasonal conditions, have been intensively studied. The genetic and molecular mechanisms underpinning diapause development are less well known. We took a candidate gene approach to study prediapause gene expression patterns in the Colorado potato beetle (Leptinotarsa decemlineata), an invasive insect that has rapidly spread northwards to high seasonality environments. Newly eclosed beetles originating from southern (Italy) and northern (Russia) Europe were reared under short- [12 h light (L):12 h dark (D)] and long-day (18L:6D) photoperiods for 10 days. This time period includes the sensitive period for the photoperiodic induction and initiation of diapause. Gene expression trajectories of 12 diapause-related genes (regulatory, metabolic and stress-resistance) were analysed from 0-, 5- and 10-day-old beetles. Gene expression differences increased with age, deviating significantly between populations and photoperiods in 10-day-old beetles. The gene expression profiles, particularly those related to energy metabolism and stress-resistance, indicate that beetles originating from Russia also prepare for diapause under the long-day photoperiod and show qualitative differences in the diapausing phenotype. Our study shows that population-dependent differences seen in behavioural and physiological traits connected with diapause in L. decemlineata are also evident in the expression trajectories of diapause-related genes.

Variability in metabolic rate and gas exchange patterns of the Colorado potato beetle of winter and prolonged diapauses

“…Lehmann et al . () regard it as a strategy for conserving water, as far as the duration of open phase of DGE is kept to a minimum. According to our observations, the strength of pumping movements decreases with longer diapause.…”

“…This is interpreted as an energetic benefit relating to heightened gas exchange efficiency in underground hypoxic or hypercapnic environments. Lehmann et al (2014) regard it as a strategy for conserving water, as far as the duration of open phase of DGE is kept to a minimum. According to our observations, the strength of pumping movements decreases with longer diapause.…”

“…It is assumed that the Colorado potato beetle population has adapted to the cold conditions and the presence of individuals with longlasting diapause supports the persistence of the population over unsuitable years. Although studies of the different life and diapause stages of Colorado potato beetle are reported extensively (Ushatinskaya, , , ; Senanayake et al ., ; Tauber & Tauber, ; Piiroinen et al ., ; Yocum et al ., ; Lehmann et al ., ), they still remain scarce with respect to the respiratory patterns of the species (Vanatoa et al ., ; Lehmann et al ., ; Kuusik et al ., ). We consider that the overwintering characteristics and respiratory patterns are related and therefore the respiratory physiology methods can provide reliable information about the population structure.…”

Responses in metabolic rate to changes in temperature in diapausing Colorado potato beetle Leptinotarsa decemlineata from three European populations

“…Even though the relative contribution of respiratory water loss to total water loss is a subject of conjecture and debate (Lighton, 1996;Danks, 2000;Groenewald et al, 2014), it is likely significant, especially during prolonged periods of rest (Chown, 2002;Chown & Nicolson, 2004). Thus, beetles from the northern populations, which experience much longer overwintering periods than the southern population (a mean of 8 months in Petroskoi versus 5 months in Padua), might have undergone selection for an enhanced water conserving respiration strategy, where the duration of the open phase during DGCs is kept to a minimum (Lehmann et al, 2014b). However, because water loss rates are not directly measured in the present study, no assessment can be made as to whether decreased DGC frequency is associated with decreased water loss.…”

Range-Expanding Pests and Pathogens in a Warming World

“…Some differentiation in the physiological response to day length has been detected between Italian and Russian populations. In particular, expression of genes related to energy metabolism and stress tolerance indicates that Russian beetles prepare for diapause even under long day lengths (82).…”