Sequencing, Expression, and Functional Analyses of Four Genes Related to Fatty Acid Biosynthesis During the Diapause Process in the Female Ladybird, Coccinella septempunctata L.

Mei Xiang,Hong-Zhi Zhang,Li-Sheng Zhang,Lian-Sheng Zang,Jian-Jun Mao,Yu-Yan Li,Xiao-Yu Jing,Meng-Qing Wang

doi:10.3389/fphys.2021.706032

Abstract

The ladybird Coccinella septempunctata L., a predatory insect, serves as an excellent biological control agent against common agricultural pests. It undergoes a diapause phenomenon, during which a large amount of fat accumulates in the abdomen. A comprehensive analysis of this lipid accumulation can reveal the molecular mechanisms underlying diapause regulation, which can be exploited to improve the shipping and transport of the insect for agricultural applications. In this study, we compared the transcriptome of C. septempunctata during non-diapause, diapause, and post-diapause and screened four key genes related to lipid metabolism. The cDNA of these four relevant enzymes, acetyl-CoA carboxylase (ACC), long-chain fatty acid-CoA ligase (ACSL), elongase of very-long-chain fatty acids (ELO), and very-long-chain 3-oxoacyl-CoA reductase (KAR), were cloned using reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends. Their expression profiles were analyzed during the preparation and maintenance phases of diapause and the post-diapause phase. The functions of these four key enzymes in diapause were further verified using RNA interference. All four genes were most closely related to the homeotic gene from Tribolium castaneum. The expression profiles of these four genes were significantly affected under diapause-inducing conditions; their expression level was the highest in the diapause preparation phase, and it gradually decreased with the diapause induction time. RNA interference showed that the target genes play important roles in fat storage during early diapause, and the decrease in their expression leads to a decrease in lipid content in C. septempunctata. These results indicate an important role of ACC, ACSL, ELO, and KAR in lipid accumulation. Our findings could help elucidate the production and accumulation of lipids by insects during the preparation for diapause and improve biological control.

Highlights

The widely distributed seven-spotted ladybird Coccinella septempunctata L., a typical natural predator of agricultural pests, preys on various types of aphids, commonly found in fruit trees and crops
The four genes related to fatty acid biosynthesis identified in C. septempunctata were designated as CsACC, CsACSL, CsELO, and CsKAR
This study demonstrated that CsACC, CsACSL, CsELO, and CsKAR play a pivotal role in lipid accumulation in C. septempunctata, as the total lipid content and abdominal lipid accumulation were significantly reduced after gene silencing

Summary

Introduction

The widely distributed seven-spotted ladybird Coccinella septempunctata L., a typical natural predator of agricultural pests, preys on various types of aphids, commonly found in fruit trees and crops. Coccinella septempunctata is distributed across various regions (Hodek and Michaud, 2008; Simelane et al, 2008). It has a characteristic diapause period during which the adult diapause elytra are light in color and remain yellow for a long period. Ovarian development is halted and a large amount of fat accumulates in the abdomen (Wang et al, 2013). This physiological change can provide energy required by the insect to withstand the diapause period, ensuring its survival in a hostile environment (Ren et al, 2016). Further understanding of the mechanisms regulating diapause can help improve longdistance shipping and long-term storage of this insect (Ren et al, 2016), thereby promoting its important role as an agricultural commodity in biological control (Turnock et al, 2003)

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Conclusion