Location: Hard Winter Wheat Genetics Research Unit
Title: Comparative gut transcriptome analysis reveals differences between virulent and avirulent biotypes of the Russian wheat aphid, Diuraphis noxia Authors
|Anathakrishnan, Radhika -|
|Sinha, Deepak -|
|Murugan, Marimuthu -|
|Zhu, Kun Uan -|
|Zhu, Yu Cheng|
|Smith, Charles -|
Submitted to: Arthropod-Plant Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 11, 2014
Publication Date: March 21, 2014
Citation: Anathakrishnan, R., Sinha, D., Murugan, M., Zhu, K., Chen, M., Zhu, Y., Smith, C.M. 2014. Comparative gut transcriptome analysis reveals differences between virulent and avirulent biotypes of the Russian wheat aphid, Diuraphis noxia. Arthropod-Plant Interactions. 8(2):79-88. Interpretive Summary: The Russian wheat aphid is a destructive pest of cereal crops. Growing resistant wheat is the best way to control the aphid. However, a new biotype (biotype 2) can overcome many known resistance genes in wheat cultivars. Dn4 is a dominant resistance gene that protects wheat against Russian wheat aphid biotype 1 infestation, but is susceptible to biotype 2. To identify genetic factors related to Russian wheat aphid virulence, we analyzed the genes expressed in the gut of Russian wheat aphid biotypes 1 and 2, and found that different genes were expressed between these two biotypes. A gene encoding the tRNA-Leu was significantly up-regulated in the gut of biotype 2, suggesting that leucine metabolism is a critical factor for biotype 2 survival on plants that carry Dn4. Higher expression levels of protease inhibitor genes were detected in the avirulent biotype 1, but higher expression levels of several protease genes were detected in the biotype 2, suggesting that biotype 1 produces protease inhibitors in response to elevated plant proteases, whereas biotype 2 produces proteases to overcome Dn4 resistance. This research is a step forward to understand how Russian wheat aphid biotype 2 overcomes plant resistance conferred by the Dn4 resistance gene in wheat.
Technical Abstract: The Russian wheat aphid, Diuraphis noxia, is a destructive pest of cereal crops that exhibits virulence to wheat D. noxia resistance genes; therefore, it is important to identify factors related to D. noxia virulence. The insect gut, the primary site of defense to ingested toxins, may exhibit differences in gut gene composition or a differential level of gene expression in virulent insects. Comparative analyses of the gut transcriptomes of virulent and avirulent D. noxia can improve understanding of aphid gut physiology and reveal factors critical to successful D. noxia - wheat interactions. A total of 4,600 clones were sequenced from gut cDNA libraries prepared from avirulent D. noxia biotype 1 and virulent biotype 2 feeding on biotype 1-resistant wheat. A majority of the sequences (66% biotype 1, 64% biotype 2) matched those in the Genbank Nonredundant database, and 59% of the biotype 1 sequences matched those of the pea aphid, Acyrthosiphon pisum; however, only 17% of the biotype 2 sequences were similar to A. pisum. RT-qPCR expression analyses confirmed that the biotype 2 gut transcriptome differs significantly from that of biotype 1. A transcript coding the tRNA-Leu gene was significantly up-regulated in the biotype 2 transcriptome, strongly suggesting that leucine metabolism is a critical factor in biotype 2 survival. Many transcripts encoding protease inhibitors occurred in the avirulent biotype 1 gut than in the gut of virulent biotype 2. However, more transcripts for proteases occurred in the biotype 2 gut than in the biotype 1 gut, suggesting that the avirulent biotype produces protease inhibitors in response to plant proteases, but that the virulent biotype produces trypsin-like and chymotrypsin-like serine protease counter-defenses to overcome biotype 1-resistant plants.