Brief Warm and Aldo-Keto Reductase Family AspiAKR1B1 Contribute to Cold Adaptation of Aleurocanthus spiniferus

Abstract

Aleurocanthus spiniferus not only damages plant leaves directly but also causes a sooty blotch due to the honeydew secreted by the nymphs and adults. This pest is widespread and seems to be spreading from low latitude to higher latitude areas where winters are typically colder, indicating an increase in its cold tolerance. Changes in temperature help insects to anticipate the arrival of winter, allowing them to take defensive measures in advance. This study examines the impacts of brief warm pulses on the low-temperature tolerance of A. spiniferus, and analyzes the physiological and biochemical mechanisms underlying its cold adaptation, utilizing seasonal differences in cold tolerance. Intermittent training at 25 °C significantly improved the survival rate of overwintering nymphs (third and fourth instar) at -7 °C. Analysis of seasonal differences in the supercooling point (SCP) and freezing point (FP) revealed that overwintering nymph had the highest cold tolerance in November. Seasonal variation in levels of cold-resistant substances were also observed, with moisture decreasing during overwintering, while fat and glycerol levels increased. Conversely, glucose, sorbitol, and trehalose levels rose significantly at the end of the overwintering period. The expression profile of cold-resistant genes indicated that the aldo-keto reductase family 1 member B1 in Aleurocanthus spiniferus (AspiAKR1B1) shows a significant decrease at the end of the overwintering period. Knocking down AspiAKR1B1 led to a marked reduction in the cold tolerance of A. spiniferus. Therefore, brief warm pulses and AspiAKR1B1 are key factors contributing to the enhanced cold tolerance of A. spiniferus. This research provides theoretical support for preventing the further spread of A. spiniferus to higher latitudes, and offers technical guidance for developing effective pest control measures.

Keywords: Aleurocanthus spiniferus; AspiAKR1B1; cold tolerance; fluctuating thermal regime.

Figure 1

Survival rate of Aleurocanthus spiniferus at −7 °C. (a): 1st instar nymph, (b): 2nd instar nymph, (c): 3rd instar nymph, (d): 4th instar nymph, (e): pseudopupae, (f): adults. Data in the figure are means ± SE. Different letters at the top of columns mean significant differences (p < 0.05) detected by one-way analysis of variance, means were compared using Tukey’s-b multiple range test.

Figure 2

Survival rate of Aleurocanthus spiniferus at different brief warm pulse treatments. (a): 1st instar nymph, (b) 2nd instar nymph, (c) 3rd instar nymph, (d) 4th instar nymph. The asterisk represents significant differences between treatments using one-way analysis of variance, means were compared using Tukey’s-b multiple range test, * p < 0.05, ** p < 0.01, and ns means no significant difference (p > 0.05).

Figure 3

The SCP and FP of Aleurocanthus spiniferus. The SCP (a) and FP (b) of 3rd instar nymph, 4th instar nymph, pseudopupae, female and male from the natural population of Aleurocanthus spiniferus in November. The SCP and FP of 3rd instar nymph (c,f), 4th instar nymph (d,g), pseudopupae (e,h) from the natural population of Aleurocanthus spiniferus in different months. Different shapes and colours represent different developmental stages (a,b) and months (c–h). The asterisk represents significant differences between treatments using one-way analysis of variance, means were compared using Tukey’s-b multiple range test, ** p < 0.01, *** p < 0.001.

Figure 4

Moisture content (a) and fat content (b) of Aleurocanthus spiniferus nymph in different months. Data in the figures were means ± SE. Different colored circles represent different months. The different letters at the top of columns mean significant difference (p < 0.05) detected by one-way analysis of variance, means were compared using Tukey’s-b multiple range test.

Figure 5

The polyol and sugar content of Aleurocanthus spiniferus nymph in March and November. The asterisk represents significant differences of low molecule substance contents between March and November using two-tailed Student’s t-test, * p < 0.05, ** p < 0.01, *** p < 0.001, while ns means no significant difference (p > 0.05).

Figure 6

Expression levels of AspiAKR1A and AspiAKR1B in different months. (a): AspiAKR1A1, (b): AspiAKR1A2, (c): AspiAKR1A3, (d): AspiAKR1B1, (e): AspiAKR1B2, (f): AspiAKR1B3. Data in the figure are means ± SE. Different colored circles represent different months. The different letters at the top of columns indicate significant difference of AspiAKR1 relative expressions between different months (p < 0.05) detected by one-way analysis of variance, means were compared using Tukey’s-b multiple range test. ns means no significant difference (p > 0.05).

Figure 7

RNAi treatment of AspiAKR1B1. (a): Effect of RNAi treatment on the transcript levels of AspiAKR1B1 and lta. (b,c): The SCP and FP of dsAKR1B1 and dslta treatments. (d): The mortality of dsAKR1B1 and dslta treatments at −7 °C. Asterisks indicate significant differences between treatments using two-tailed Student’s t-test, * p < 0.05, ** p < 0.01, *** p < 0.001, while ns means no significant difference (p > 0.05).