Silencing of a putative alanine aminotransferase (ALT) gene influences free amino acid composition in hemolymph and fecundity of the predatory bug, Cyrtorhinus lividipennis Reuter

Authors: AHMAD, SHERAZ - Yangzhou University; JIANG, LU - Yangzhou University; ZHENG, SUI - Yangzhou University; CHEN, YU - Yangzhou University; ZHANG, JIE YU - Yangzhou University; Stanley, David; MIAO, HONG - Yangzhou University; GE, LIN Q. - Yangzhou University

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2021
Publication Date: 7/19/2021
Citation: Ahmad, S., Jiang, L., Zheng, S., Chen, Y., Zhang, J., Stanley, D.W., Miao, H., Ge, L. 2021. Silencing of a putative alanine aminotransferase (ALT) gene influences free amino acid composition in hemolymph and fecundity of the predatory bug, Cyrtorhinus lividipennis Reuter. Archives of Insect Biochemistry and Physiology. 108(2). Article e21836. https://doi.org/10.1002/arch.21836.
DOI: https://doi.org/10.1002/arch.21836

Interpretive Summary: Asian rice cropping systems are challenged by three planthopper species. These are very small insects that inflict heavy damage on rice plants in two ways, by direct damage to the plants and also by transmitting plant pathogenic viruses to them. In efforts to reduce insecticide use in rice cropping systems, there is considerable interest in applying biological control agents, including planthopper predators and pathogens. So far, there is relatively little information on the biology and biochemistry of planthopper predators. The predatory bug, Cyrtorhinus lividipennis, feeds on planthopper eggs and has considerable potential as a biological control agent. Here, we report on the biochemistry and molecular biology of a key protein that impacts metabolism in the predatory bug. The protein is present in all life stages of the bug. Inhibiting expression of the protein leads to severe reductions in the insect's reproduction. This new information will be used by a wide range of scientists who are working to develop the predatory bug into an effective biological control agent. This will support efforts to produce healthy rice and rice products for consumption on all major continents. Consumers will benefit from healthy foods produced with reduced agricultural chemicals.

Technical Abstract: In Asian rice systems, Cyrtorhinus lividipennis Reuter is an important predator that preys on rice planthopper eggs and young nymphs, as a primary food source. Because alanine aminotransferase (ALT) acts in many physiological and biochemical processes in insects, we investigated this important enzyme in C. livivipennis. We cloned the full-length cDNA of C. lividipennis ClALT. Expression analysis showed higher expression in the fat body and midgut compared to other tissues. It is expressed in all C. lividipennis developmental stages and at least four organs. Silencing ClALT by per os RNAi significantly decreased the ClALT enzyme activity and ClALT expression compared to dsGFP-treated controls at two days after emergence (DAE). Silencing ClALT influenced free hemolymph amino acid compositions, resulting in a reduction of Aspartic acid (Asp) and Alanine (Ala) proportions, and increased Cysteine (Cys) and Valine (Val) proportions in females at two DAE. dsClALT treatments led to decreased soluble total protein concentrations in ovary and fat body, to reduced vitellogenin (Vg) expression, body weight, and numbers of laid eggs. The dsRNA treatments also led to prolonged preoviposition periods, and hindered ovarian development. Western blot analysis indicated that silencing ClALT also led to reduced fat body Vg protein abundance at two DAE. These data support our hypothesis that ClALT influences amino acid metabolism and fecundity in C. lividipennis.