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RNAi Sniper Technology Alters Crops in Field


As a young boy weeding on his family’s southwest Louisiana rice farm in 1960, John Killmer was startled to see a small airplane cross over his field. His father identified it as a crop duster passing to spray a neighbor’s weeds. Only a year later, the Killmer farm was also using airplanes for weed spraying. The leap from hand-weeding to aerial herbicide application had a tremendous impact on Killmer, setting him on a quest toward agricultural technology innovation.

Killmer is now part of a vanguard related to a major change in farming. The agriculture industry may be on the cusp of an unprecedented takeoff with the advent of ribonucleic acid interference (RNAi) – a sniper’s bullet technology with implications for every aspect of crop growth. Disease, drought, pests and much more are in the crosshairs, and the possibilities for this non-GMO crop alteration technology seem boundless.

Think of RNAi as a covert operator: It slips in, shuts down a gene temporarily, and is gone. Got an insect flare-up in corn or soybeans? Reach into the arsenal and feed the pests a gene-specific RNAi aimed at shutting down their digestive tracts. The pests die; the crop thrives; no genetic modification required.

RNA is a template produced from DNA and used to make protein. RNAi uses a tiny piece of RNA to interfere with the template building process. RNAi carries tremendous potential to alter crop plants in the field in a non-GMO manner. “Some believe the alterations can be as powerful as current GMO systems now in use,” says Killmer, CEO of APSE, a company specializing in technology to create bulk amounts of RNA. “The RNAi concept most often tossed around is drought resistance. Plant a normal crop variety and if drought shows up, apply an RNAi effective in altering crops during drought.”

Knockdown

Essentially, RNAi is a non-GMO ‘as needed’ path to crop traits. GMO modifications are heritable, but RNAi application is a one-shot, knockdown effect and isn’t passed on to progeny. “The cool thing about RNAi? It basically interferes with the genome blueprint. No blueprint – you can’t make the part. In insects, there is just enough temporary interference to keep the organisms from surviving,” says Meg Allen, research entomologist, Biological Control of Pests Research Unit, Stoneville, Miss.

The potential for RNAi applications blanket all facets of agriculture, from flavor and plant growth to pests and weed control. RNA is an extremely fragile molecule, and RNAi success in broad acre agriculture is challenged by delivery method. How to get RNAi into a plant? Killmer believes early RNAi uses will be commercialized to bypass delivery obstacles. As a topical treatment, application could be made by airplane, sprayer or seed treatment. “If you want insects to eat it, just have it sitting out, rather than inside the leaf,” Killmer says.

Allen tested RNAi on tarnished plant bug, a major cotton nemesis which doesn’t respond to Bt tools. She fed the insects bits of RNA, but found no effect. Why? The saliva of tarnished plant bug degraded the RNA material – it spits before it swallows. Her project was groundbreaking and managed to inspire other RNA work which may see fruition across farmland. “If you can deliver non-degraded, double-stranded RNA to a pest and it matches a gene the pest needs to survive, the pest will become sick or die. The DNA code is so specific, the likelihood of RNAi affecting anything but the pest it’s designed for is extremely low,” Allen says.

RNA is found everywhere and a person typically consumes a gram of RNA in fruit, vegetables, grain and meat each day. EPA is looking at regulatory RNAi issues and is interested in off-target effects. The active part of RNAi is short-lived, very specific, and hits a narrow zone. “RNAi has the potential to be remarkably safe and very effective, due to its specificity,” Allen notes.

Cost Questions

Along with delivery challenges, RNAi production costs are a major hurdle for use in agriculture. Although RNAi is effective at a low dose rate — grams per acre — early RNAis cost hundreds of thousands of dollars per gram, according to Killmer. APSE is focused on bringing down RNA costs and maintaining stability of RNA on the leaf and seed. (APSE is not addressing how to get RNA inside a leaf.) As interest grows and investment builds, the dollar numbers have dropped for RNAi production. APSE is targeting a $2 per gram price – a seismic shift in cost.

Killmer is not involved with discovery work comparable to the major ag companies breaking ground on which types of RNAi work best. “What are we saying? When you find an RNAi that works, we’re going to find a method to make that precise RNAi efficiently so it can be used commercially,” Killmer says.

By 2020, Killmer believes RNAi will be available in agriculture as a spray-on for insect control. “It’s no understatement to say RNAi could impact every part of a farmer’s crop production process.”

Source: Chris Bennett, Farm Journal

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