Gu Gong, Long-Yu Yuan, Yi-Feng Li, Hang-Xiang Xiao, Yan-Fang Li, Yang Zhang, Wei-Jian Wu, Zhen-Fei Zhang

Sci Rep.; 2022 Feb 25;12(1):3205.  doi: 10.1038/s41598-022-07106-6.

Abstract

The brown planthopper (BPH), Nilaparvata lugens, is an important pest that affects rice (Oryza sativa) production in Asia. The flavone tricin (5,7,4'-trihydroxy-3',5'-dimethoxy flavone) is a valuable secondary metabolite commonly found in rice plants that can defend rice plants against infestation by BPH. BPH damage can reduce the metabolic level of tricin in rice. Our preliminary transcriptome research results showed that BPH salivary protein 7 (NlSP7), is highly responsive to tricin stimuli. However, the function of NlSP7 in mediating the interaction between the rice plant and the BPH is unknown. In this study, we cloned the NlSP7 gene in N. lugens and found that its mRNA level was greater in the presence of high tricin content than low tricin content, regardless of whether the BPHs were fed a rice plant diet or an artificial diet containing 100 mg/L tricin. Knocking down NlSP7 resulted in BPH individuals spending more time in the non-penetration and pathway phase, and less time feeding on the phloem of rice plants. These changes decreased BPH food intake, feeding behavior, and fitness, as well as the tricin content of the rice plants. These findings demonstrate that the salivary protein 7 of BPH functions as an effector for tricin metabolism in rice.

See https://pubmed.ncbi.nlm.nih.gov/35217680/

Figure 1: Characterization of NlSP7. (A) CDS sequence of NlSP7. The solid underline indicates the signal peptide as predicted by SignalP 5.0. The asterisk (*) indicates the stop codon. The different short-repeat regions are indicated by different colors. (B,C) The bottom panels show the mean transcript levels ± SD (n = 30) of NlSP7 in whole bodies at various developmental stages (B) and in different tissues (C). RNA was extracted from nymphs at 1–5 days and female brachypterous brown planthoppers reared on Rathu Heenati rice at 1, 3, 5, 7, 9, 11, 13, and 15 days. Hd, head; Sg, salivary gland; Ov, ovary; Mg, midgut; Lg, leg; Fb, fat body was extracted from BPH adults.