Secretory laccase 1 in Bemisia tabaci MED is involved in whitefly-plant interaction

Abstract

The whitefly Bemisia tabaci is a phloem-feeding pest that lives predominantly on herbaceous species and causes serious damage to hosts. Whitefly saliva is thought to contain proteins that modulate plant defences and facilitate feeding. A predicted secreted protein, laccase 1 (LAC1), was found in the salivary gland transcriptome of B. tabaci and might be existed in the watery saliva of B. tabaci. As LAC1 has a potential role in detoxification of secondary plant compounds in insects, we speculated that it may participate in the insect’s response to plant defences. Here, we cloned the complete cDNA of LAC1 and found that (1) LAC1 was highly expressed in the salivary gland (SG) and midgut; (2) LAC1 transcript level in head (containing SG) was 2.1 times higher in plant-fed than in diet-fed whiteflies and 1.6 times higher in the head and 23.8 times higher in the midgut of whiteflies that fed on jasmonic acid (JA)-sprayed plants than on control plants; and (3) silencing LAC1 decreased the survival rate of plant-fed whiteflies but had a marginal effect on whiteflies raised on an artificial diet. These results indicate that LAC1 enables whiteflies to overcome the chemical defences of host plants and might act as an effector in saliva.

Molecular characterization and gene silencing of Laccase 1 in the grain aphid, Sitobion avenae

“…Yang et al. () also found that Lac 1 had the highest levels of expression in the fourth instar and adult stage of B. tabaci .…”

“…First, Laccase 1 was obtained from S. avenae in our study, and three different conserved copper domains, Type‐1 (T1), Type‐2 (T2), and Type‐3 (T3) (Dwivedi, Singh, Pandey, & Kumar, ), were found in the sequence, indicating that SaLac 1 is a member of the blue copper‐containing polyphenol oxidase family and has oxidative activity. Studies demonstrate that Lac 1 is a secreted protein, and laccase activity has been detected in the watery saliva of B. tabaci and N. cincticeps (Hattori, Konishi, Tamura, Konno, & Sogawa, ; Yang et al., ). However, in our study, Lac 1 in S. avenae was predicted as attached to the exterior of the plasma membrane.…”

“…Orthologous Lac 1 genes have been identified in many insect species, including the whitefly, Bemisia tabaci (Yang et al., ); green rice leafhopper, Nephotettix cincticeps (Hattori et al., ), and pea aphid Acyrthosiphon pisum (Liang, ). Lac 1 is involved in iron homeostasis and immune defense of insects.…”

Transient Expression of Whitefly Effectors in Nicotiana benthamiana Leaves Activates Systemic Immunity Against the Leaf Pathogen Pseudomonas syringae and Soil-Borne Pathogen Ralstonia solanacearum

“…The candidate effector cDNAs encode proteins annotated as follows: 2G5, an unknown protein, and 6A10, large subunit ribosomal RNA ( Figure 6A). The expression levels of these genes did not significantly differ from that of the positive control, Lac1 (Figure 6A), encoding a recently identified whitefly effector (Yang et al, 2017). Collectively, of the three clones, only clones 2G5 and 6A10 represent solid candidate whitefly effectors.…”

“…Whitefly saliva is thought to contain proteins that modulate plant defense responses and facilitate feeding. Secreted whitefly laccase 1 (LAC1) and small RNAs have been identified and are thought to help the insect overcome plant immunity responses (van Kleeff et al, 2016;Yang et al, 2017). …”