Clever larvae switch off protection mechanism
2 Jul 2010 by Evoluted New Media
Plants under attack from Hessian fly larva are able to protect themselves by ramping up production of surfaces waxes and cutin according to new research from Purdue University - they also found that the larvae can hijack this defence.
Plants under attack from Hessian fly larva are able to protect themselves by ramping up production of surfaces waxes and cutin according to new research from Purdue University - they also found that the larvae can hijack this defence.
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Scanning Electron Micrograph showing a virulent first-instar Hessian fly larva feeding on a susceptible wheat plant Credit: Dr. Subhashree Subramanyam of Purdue University |
Christie Williams, associate professor of entomology and research scientist with the US Department of Agriculture, and colleague Jill Nemacheck found that the genes thought to be responsible for cutin and wax production are affected by fly larvae.
“The fly larvae seem to hijack the regulation of certain plant genes and cause the plant to turn off defences that would keep it from becoming susceptible,” said Williams, “If we could find a way to block the larvae from affecting genes that are responsible for cutin production or find a way to keep that cutin from degrading, the plants might be more resistant.”
The duo used polymerase chain reactions to quantify gene expression of genes responsible for cutin and wax production. They compared the amount of messenger RNA– which carries instructions to tell cells to produce proteins responsible for generating cutin or wax – in different plant samples. Less messenger RNA in the original tissue sample indicates a lower level of genes expression, and ultimately lower cutin or wax production.
“In resistant plants, expression of genes that control wax and cutin production was increased,” said Nemacheck, “Susceptible plants had a decrease in the expression of those genes.”
Plants were determined to have become susceptible through staining tissue with red dye that was placed on larva feeding sites. Resistant plants with increased cutin production had slight spotting along the leaves, but susceptible leaves absorbed the dye because it was able to seep into the plant’s cells due to lack of cutin.
Williams measured the changes in waxes and cutin production using gas chromatography. Samples from feeding sites – where larvae deposit saliva to make the leaf surface more permeable – were carried by gas through a liquid column to separate the chemicals.
