D-3-phosphoglycerate dehydrogenase from the silkworm Bombyx mori: Identification, functional characterization, and expression

Characterization of a glutamate-cysteine ligase in Bombyx mori

Glutamate-cysteine ligase (GCL) is a crucial enzyme involved in the synthesis of glutathione (GSH). Despite various studies on glutathione transferase, and its essential role in detoxification and resistance to oxidative stress, GSH synthesis has not been described in Bombyx mori (silkworms) to date. Silkworms form part of the lepidopterans that are considered as a model of agricultural pests. This study aimed to understand the GSH synthesis by GCL in silkworms, which may help in developing insecticides to tackle agricultural pests. Based on the amino acid sequence and phylogenetic tree, the B. mori GCL belongs to group 2, and is designated bmGCL. Recombinant bmGCL was overexpressed and purified to ensure homogeneity. Biochemical studies revealed that bmGCL uses ATP and Mg²⁺ to ligate glutamate and cysteine. High expression levels of bmgcl mRNA and GSH were observed in the silkworm fat body after exposure to insecticides and UV-B irradiation. Moreover, we found an increase in bmgcl mRNA and GSH content during pupation in the silkworm fat body. In this study, we characterized the B. mori GCL and analyzed its biochemical properties. These observations indicate that bmGCL might play an important role in the resistance to oxidative stress in the silkworms.

The Phosphoserine Phosphatase Alters the Free Amino Acid Compositions and Fecundity in Cyrtorhinus lividipennis Reuter

The mirid bug Cyrtorhinus lividipennis (Reuter) is an important predator that consumes eggs and young nymphs of the brown planthopper Nilaparvata lugens as a primary food source and thus becomes an important member of the rice ecosystem. We identified and characterized the ClPSP gene in C. lividipennis encoding the phosphoserine phosphatase enzyme. The ClPSP has an open reading frame (ORF) of 957 bp encoding a protein with a length of 294bp and it possesses a haloacid dehalogenase-like (HAD) hydrolase, phosphoserine phosphatase, eukaryotic-like (HAD_PSP_eu) conserved domain. Furthermore, the in silico analysis of the ClPSP gene unveiled its distinct characteristics and it serves as a key player in the modulation of amino acids. The ClPSP showed expression in all developmental stages, with higher expression observed in the ovary and fat body. Silencing the ClPSP by RNA interference (RNAi) significantly decreased PSP enzyme activity and expression compared to dsGFP at two days after emergence (2DAE). The dsPSP treatment altered free hemolymph amino acid compositions, resulting in a significant reduction of serine (Ser) and Arginine (Arg) proportions and a significant increase of Threonine (Thr), Cystine (Cys), and Tyrosine (Tyr) in the C. lividipennis female at 2 DAE. Additionally, a hindered total protein concentration in the ovary and fat body, and reduced vitellogenin (Vg) expression, body weight, and number of laid eggs, were also observed. The same treatment also prolonged the preoviposition period and hindered ovarian development. Our data, for the first time, demonstrated the influential role of the PSP gene in modulating the fecundity of C. lividipennis and provide a platform for future insect pest control programs using the PSP gene in modulating fecundity.