Author
SUBRAMANYAM, SUBHASHREE - Purdue University | |
SARDESAI, NAGESH - Purdue University | |
MINOCHA, SUBHASH - University Of New Hampshire | |
ZHENG, CHENG - Purdue University | |
Shukle, Richard | |
Williams, Christie |
Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/22/2014 Publication Date: 1/16/2015 Citation: Subramanyam, S., Sardesai, N., Minocha, S., Zheng, C., Shukle, R.H., Williams, C.E. 2015. Hessian fly larval feeding triggers enhanced polyamine levels in susceptible but not resistant wheat. Biomed Central (BMC) Plant Biology. 15:3. doi:10.1186/s12870-014-0396-y. Interpretive Summary: A better understanding of Hessian fly manipulation of susceptible wheat processes is needed in order to identify points of vulnerability that can be genetically addressed. We found that larvae cause wheat plants to produce high levels of polyamines, compounds that are beneficial to the larval development. These results are important because polyamine pathways may be viable targets for silencing in wheat in order to deprive larvae of a needed nutrient and thus increase resistance. Technical Abstract: Insect herbivores depend on dietary amino acids and polyamines (PA) for their growth and development. We have analyzed polyamine metabolism during the interaction of wheat with one of its major insect pests, the Hessian fly [Mayetiola destructor (Say)]. The wheat-Hessian fly interaction operates in a gene-for-gene manner resulting in either compatible (susceptible plant) or incompatible (resistant plant) interactions. Feeding by Hessian fly larvae results in significantly higher transcript levels of genes encoding key PA biosynthesis enzymes (Ornthine decarboxylase, S-adenosyl methionine decarboxylase and S-adenosyl methionine synthetase) in susceptible plants as compared to resistant and uninfested plants. Expression profiles for genes from the amino acid biosynthesis pathway (Pyrroline-5-carboxylate synthetase, Arginine decarboxylase and Acetylornithinase) that feed into the PA biosynthesis pathway indicate preferential synthesis of wheat polyamines from ornithine instead of arginine. Increase in transcripts of PA pathway genes is accompanied by increased S-adenosyl methionine decarboxylase activity, as well as higher levels of free polyamines (putrescine, spermidine and spermine) in susceptible plants. A concurrent increase in PA levels in the virulent larvae inhabiting and feeding on the susceptible plant suggests that plants are the source of polyamines for the larvae. Inhibition of Ornthine decarboxylase activity in the susceptible plants using DL-'- difluoromethylornithine resulted in reduction of virulent larval size highlighting the importance of polyamines in their diet. Our results demonstrate the possible manipulation of metabolic pathways in wheat by virulent Hessian fly larvae leading to increased production of polyamines that are utilized by these larvae for their own growth and development. |