Characterisation Of Salivary Candidate Effectors Of BtQ0F1 And BtQ2477 In Bemisia Tabaci

The whitefly Bemisia tabaci (Hemiptera:Aleyrodidae) is a phloem sap-feeder. In recent years, the Middle East Asia Minor 1 (MEAM1) and Mediterranean (MED) species of the B. tabaci species complex have invaded many regions of China and become a serious threat to agriculture production. Whitefly damages the plants by direct feeding and vectoring the begomoviruses, both of which are tightly associated with the feeding of whitefly. Previous studies indicated that salavry secretion was needed during the feeding process of sap-feeding insects to help probe and feed. Besides, the effectors in the salivary can manipulate plant defence response in favor of the insect. Until now, there are few reports about the effectors in whitefly salvary and their roles in whitefly-plant interactions.Here we chose two candidate effectors from the transcriptome of the MED whitefly salvary gland, namely BtQOF1 and BtQ2477, then we performed sequence analysis, bioassays and expression analyses of plant defence genes to explore the roles of the two genes in whitelfy-plant interactions.1.Squence and function analyses of BtQOF1BtQOF1 gene encodes a protein of 259 amino acids, and the predicted protein molecular weight is 25.89 kDa with an isoelectric point of 4.40. Bioinformatics analysis indicated that BtQOF1 protein is a secreted protein without transmembrane domain but with a signal peptide. There is no BtQOF1 homologous gene found in the GenBank.Transient expression of BtQOFl in tabaco by agro-bacteria infiltration could significantly increase the whitefly survival rate. Gene silencing of whitefly BtQOF1 by dsRNA feeding resulted in lower surival.In addition, transient expression of BtQOF1 in tabaco by agro-bacteria infiltration supressed the JA,BR and SA signaling pathway, showing that protein encoded by BtQOFl was capable of manipulating the plant defence response. The target band was visualized when we used specific rabbit ployclonal antibody against protein encoded by BtQOFl as first antibody to detect protein extracts from MED whitefly whole body.(2) Squence and function analyses of BtQ2477BtQ2477 gene encodes a protein of 175 amino acids, and the predicted protein molecular weight is 25.00 kDa with an isoelectric point of 7.44. Bioinformatics analysis indicated that BtQ2477 has a signal peptide. This protein belongs to a family of small proteins, which appears to be involved with dealing with mis-folded proteins in the endoplasmic reticulum.Transient expression of BtQ2477 in tabaco by agro-bacteria infiltration resulted in significant increase in whitefly survival and fecundity. In addition, the expression of genes involved in tabaco JA and SA signaling pathway were only marginally altered, suggesting that BtQ2477 might be involved in some other signaling pathways.To sum up, the candidate effectors BtQOF1 and BtQ2477 of whitefly appear to play important roles in whitefly-host plant interaction. Transient expression of BtQOF1 or BtQ2477 resulted in higher survival, while silencing of BtQOF1 gene resulted in lower survial. The increase of survial of whitefly after transient expression of BtQOFl might be due to the manipulation of tabaco JA, SA and BR signaling pathways, however more effort is warranted to investigate the munipulation of host plant defence response by BtQ2477.