Modulation of nonessential amino acid biosynthetic pathways in virulent Hessian fly larvae (Mayetiola destructor), feeding on susceptible host wheat (Triticum aestivum)

Authors: SUBRAMANYAM, SUBHASHREE - Purdue University; Nemacheck, Jill; SHREVE, JACOB - Purdue University; Schemerhorn, Brandi; SHUKLE, RICHARD - Former ARS Employee; Williams, Christie

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2018
Publication Date: 1/11/2018
Citation: Subramanyam, S., Nemacheck, J.A., Shreve, J., Schemerhorn, B.J., Shukle, R.H., Williams, C.E. 2018. Modulation of nonessential amino acid biosynthetic pathways in virulent Hessian fly larvae (Mayetiola destructor), feeding on susceptible host wheat (Triticum aestivum). Journal of Insect Physiology. 105:54-63. https://doi.org/10.1016/j.jinsphys.2018.01.001.
DOI: https://doi.org/10.1016/j.jinsphys.2018.01.001

Interpretive Summary: Future strategies for minimizing Infestation of wheat by Hessian fly will require understanding the interaction at the molecular level so that vulnerabilities can be targeted for new types of resistance. Quantifying the expression of sixteen genes involved in larval synthesis of amino acids revealed that the host plant does not supply amino acids in the optimal quantities for insect development. Consequently, the larvae must utilize energy to convert abundant amino acids into those that are in short supply. The larval genes that are highly activated for this purpose may prove to be useful targets for gene silencing in order to degrade the health of the insect. This information will be valuable for plant breeders and can ultimately lead to higher quality grains for consumers.

Technical Abstract: Hessian fly (Mayetiola destructor), an obligate plant-parasitic gall midge, is an important dipteran pest of wheat (Triticum aestivum). The insect employs an effector-based feeding strategy to reprogram the host plant to be nutritionally beneficial for the developing larva by inducing formation of protein- and sugar-rich nutritive tissue in susceptible wheat Previously, increased levels of certain essential (EA) and nonessential amino acids (NA) in the host nutritive tissue were reported. Here we annotated 16 genes encoding NA biosynthesis pathway (NABP) enzymes in Hessian fly, and correlated expression profiles of transcripts in first- and second-instar larvae with previously reported levels of NAs in the susceptible host after larval attack. The larval transcripts for NABP genes for several NAs declined in association with the formation of host nutritive tissue suggesting efficient utilization of the increased host NAs by Hessian fly larvae. However, insufficient amounts of some plant-derived NAs may have resulted in the de novo synthesis of these NAs in the Hessian fly larvae. Additionally, the increased transcripts for some NABP genes in neonates possibly play a crucial role in providing larvae with the requisite NAs for sustaining growth prior to the formation of host nutritive tissue. Thus the modulation of NABP gene expression in Hessian fly depends on (i) ability to utilize increased levels of NAs in the host nutritive tissue induced by larval feeding, (ii) sufficient reserves being accumulated during previous developmental stages of the insect, and (iii) increased dietary demands to compensate for suboptimal NA levels in the host nutritive tissue.