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Title: A novel cytochrome P450 CYP6AB14 gene in spodoptera litura (Lepidoptera: Noctuidae) and its potential role in plant allelochemical detoxification

Author
item WANG, RUI - South China Agricultural University
item XIA, QING - South China Agricultural University
item Baerson, Scott
item REN, YONG - South China Agricultural University
item WANG, JIE - South China Agricultural University
item SU, YI - South China Agricultural University
item ZHENG, SI - South China Agricultural University
item ZENG, REN - South China Agricultural University

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2015
Publication Date: 3/14/2015
Citation: Wang, R.L., Xia, Q.Q., Baerson, S.R., Ren, Y., Wang, J., Su, Y.J., Zheng, S.C., Zeng, R.S. 2015. A novel cytochrome P450 CYP6AB14 gene in Spodoptera litura (Lepidoptera: Noctuidae) and its potential role in plant allelochemical detoxification. Journal of Insect Physiology. 75:56-62.

Interpretive Summary: Plants, and the herbivorous insect predators that feed on them, exist in what is essentially an 'arms race'. During the course of evolution, plants have acquired the ability to synthesize novel chemicals that interfere with the growth and development of herbivorous insects as a defensive strategy. In response, insects have developed the capacity to metabolize these inhibitory compounds, for example through the acquisition of genes encoding specialized metabolic enzymes. Cytochrome P450 proteins are enzymes often involved in the metabolism of plant toxins encountered by herbivorous insects during feeding. This work focuses on the cytochrome P450 genes of Spodoptera litura, commonly referred to as the oriental leafworm moth. This organism poses a significant threat to commercial agriculture in many parts of the world and was therefore chosen as the model organism for these studies. We show in this work that a specific Spodoptera litura P450 gene is likely involved in the metabolism of plant toxins by first severely inhibiting its expression in vivo. The resulting insects become much more sensitive to inhibition from several commonly-encountered plant toxins. Additionally, the gene (designated CYP6AB14), exhibits increased expression in untreated individuals exposed to these same inhibitory compounds. Taken together, the results from this work strongly suggest a role for CYP6AB14 in detoxifying inhibitory plant-derived compounds encountered by Spodoptera litura while feeding.

Technical Abstract: Cytochrome P450 monooxygenases (P450) play a prominent role in the adaptation of insects to host plant chemical defenses. To investigate the potential role of P450s in adaptation of the lepidopteran pest Spodoptera litura to host plant allelochemicals, an expressed sequence data set derived from 6th instar midgut tissues was first mined. A full-length cDNA sequence was generated and determined by phylogenetic analysis to belong to the CYP6AB P450 subfamily, and identified as ¬¬. Dietary supplementation of S. litura larvae with either xanthotoxin (XAN), coumarin (COU) and flavone (FLA) led to elevated CYP6AB14 transcript levels in both midgut and fat body tissues. Injection of CYP6AB14-derived double-stranded RNA (dsRNA) into S. litura individuals significantly reduced CYP6AB14 transcript levels, and resulted in increased developmental abnormalities and higher mortality rates among XAN, COU and FLA-fed larvae. Our results strongly suggest a key role for CYP6AB14 in allelochemical detoxification in S. litura.