Exploring the Caste-Specific Multi-Layer Defense Mechanism of Formosan Subterranean Termites, Coptotermes formosanus Shiraki

Abstract

The survival and foraging of Coptotermes formosanus Shiraki in a microbe-rich environment reflect the adaptation of an extraordinary, sophisticated defense mechanism by the nest-mates. We aimed to explore the host pathogen interaction by studying caste-specific volatile chemistry and genes encoding the antioxidant defense of winged imagoes, nymphs, soldiers and workers of Formosan subterranean termites. Qualitative analyses of C. formosanus Shiraki performed by HS-SPME/GC-MS showed considerable variations in the chemical composition of volatile organic compounds (VOCs) and their proportions among all the castes. Winged imagoes produced the most important compounds such as naphthalene and n-hexanoic acid. The antifungal activity of these compounds along with nonanal, n-pentadecane, n-tetradecane, n-heptadecane and methyl octanoate against the conidial suspensions of Metarhizium anisopliae and Beauveria bassiana isolates enable us to suggest that the failure of natural fungal infection in the nest is due to the antiseptic environment of the nest, which is mainly controlled by the VOCs of nest-mates. In addition, conidial germination of M. anisopliae and B. bassiana isolates evaluated on the cuticle of each caste showed significant variations among isolates and different castes. Our results showed that the conidia of M. anisopliae 02049 exhibited the highest germination on the cuticle of all the inoculated castes. Moreover, we recorded the lowest germination of the conidia of B. bassiana 200436. Caste-specific germination variations enabled us to report for the first time that the cuticle of winged imagoes was found to be the most resistant cuticle. The analysis of the transcriptome of C. formosanus Shiraki revealed the identification of 17 genes directly involved in antioxidant defense. Expression patterns of the identified antioxidant genes by quantitative real-time PCR (qPCR) revealed the significantly highest upregulation of CAT, GST, PRXSL, Cu/Zn-SOD2, TXN1, TXN2, TXNL1, TXNL2, TXNL4A and TPx genes among winged imagoes upon infection with the most virulent isolate, M. anisopliae 02049. Furthermore, soldiers showed the least expression of genes encoding antioxidant defense. Our findings indicated that the volatile chemistry of nest-mates and genes encoding antioxidant defense greatly contribute to the survival and foraging of Formosan subterranean termites in a microbe-rich habitat.

Host-pathogen interaction for screening potential of Metarhizium anisopliae isolates against the date-palm dust mite, Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae)

“…Results showed significant differences in the SOD activities of date-palm dust mites calculated at different times (F = 48.55; df = 12, 24; P < 0.0001), with different fungal isolates (F = 85.27; df = 2, 24; P < 0.0001), and their interaction (F = 356.29; df = 4, 24; P < 0.0001) as shown in Table 2. The highest SOD activity, as depicted in the present results, among datepalm dust mites at the start of infection agrees with the results of Gretscher et al (2016) and Hussain et al (2017). However, a decline in SOD activities with time from the most virulent isolate 2049, corroborates with AlJabr et al (2018), who suggested that decline in SOD activities at a lateral infection stage from virulent isolates led to ROS elimination failure.…”

“…1). Similarly, enhanced mortality response of 2049 over time was reported against Coptotermes formosanus Shiraki (Hussain et al 2017) and Ocinara varians Walker (Hussain et al 2009). These findings showed that the effectiveness of 2049 in terms of pathogenicity against all these hosts revealed a valuable feature of being a broad-spectrum mycopathogen.…”

Toxin-Pathogen Synergy Reshaping Detoxification and Antioxidant Defense Mechanism of Oligonychus afrasiaticus (McGregor)

“…The built-in antioxidant defense mechanism protects the biological systems by regulating ROS production. However, stressful situations disproportionate the target host intrinsic antioxidants and ROS balance by eliciting oxidative stress [ 22 , 43 ]. The target host has evolved accordingly antioxidant defense system to maintain homeostasis.…”

“…The incorporation of fungal pathogens into the Integrated Pest Management program of O. afrasiaticus attained particular attention because of host specificity, persistence in target host population, numerous isolates and eco-friendly [ 18 ]. Entomopathogenic fungi especially isolates of Beauveria bassiana are well-known for their pathogenicity against different target pest species [ 19 , 20 , 21 , 22 ]. Spores of the isolates of entomopathogenic fungi impart mortality in the target pest by overcoming the complicated host defense related multiple mechanisms [ 18 , 23 , 24 , 25 , 26 ].…”

Potential Synergy between Spores of Metarhizium anisopliae and Plant Secondary Metabolite, 1-Chlorooctadecane for Effective Natural Acaricide Development

“…The potato dextrose agar plates (90-mm × 15 mm) with different concentrations (0.80, 1.60, 2.40, 3.20, and 4.00 mg/mL) of 1-Chlorooctadecane were prepared as described in detail by a previous study [45] Ten microliter spores suspension of M. anisopliae EBCL 02049 at a single concentration (1 × 10 6 spores/mL) were pipetted in the center of each PDA-plate. The plates after inoculation were sealed with parafilm.…”