The fight against Potyviruses is seemingly neverending in agriculture.
Say Hello To Another Terrible Potyvirus
As past discussions have shown, they are some of the most deadly plant viruses out there, causing huge swaths of crop death and harvest losses. Additionally, moving up a level to the family of Potyviridae shows that 30% of all plant viruses reside in this grouping, giving them a vast array of options and targets.
The sugarcane mosaic virus affects several critical crops, including sugarcane, maize, and sorghum. It typically tries to infect these crops early in their growth cycle, usually causing them to be completely barren by the time harvest comes.
First emerging in China in 1968, it was responsible for killing off thousands of kilograms of crops per acre. Also, since the virus is spread by aphids, but not always transmitted by them, attempts to focus on the aphids themselves did not do much to slow its spread.
The focus since has been on breeding resistant crops against the virus and study after study has been put out on the topic. A special target has been placed on producing resistant corn, due to corn’s prevalence within the global food supply.
Combined with other viruses, this causes corn to suffer from maize lethal necrosis disease that is currently plaguing Africa since its emergence there in 2011. Many farmers in the region of Eastern Africa are facing widespread famine from a combination of this and other plant diseases. Without ways to resist these attacks, a large number of people will die.
Stealing A Target
Two different regions in the corn genome named Scmv1 and Scmv2 are known to be sources of resistance in corn to the disease. Several years of research has gone into investigating these loci and a new publication may have a new step forward in the fight against sugarcane mosaic virus.
First off, let’s talk about the virus. The way it attacks its host plants is to corner a protein used in photosynthesis that is important for the production of energy and uses the protein to spread its own genome throughout the plant.
The genes in Scmv1 in particular binds with the particular protein ahead of the virus and stops its ability to spread via this mechanism. The issue is breeding varieties of the crop that express the genes strongly enough to cover all of the protein in question and leave no opening for the virus to invade.
Scientists from the Iowa State University and the China Agricultural University in Beijing were able to identify the exact gene within the Scmv loci, namely ZmTrxh. The gene appears to correlate strongly with corn that is resistant to sugarcane mosaic virus.
The ZmTrxh gene codes for an “atypical h-type thioredoxin”, which is essentially a redox protein critically involved in plant structures in a multitude of places. It appears that the difference between corn that is resistant or not isn’t the existence of the gene, both types have it. Instead, the difference is in where the other coding regions that regulate the gene are upstream in the genome of the gene itself.
The resistance it creates appears to be distinct from any of the other resistance pathways in corn, including the salicylic acid and jasmonic acid pathways. This means that it is a special form of defense that doesn’t connect to other dominant or recessive pathways and thus needs to be specially focused to spread to more corn varieties.
Let The Breeding Begin
But identifying the specific gene and its activities involved in sugarcane mosaic virus resistance is a major step toward producing corn of all cultivars that have the resistance. The next steps are more straightforward, but require a lot of work from scientists and farmers alike, breeding or genetically transferring the required genetic components.
Throwing the spotlight on the desired culprit is necessary for future cultivation and now agriculture researchers around the world have a method of dealing with not just sugarcane mosaic virus, but also other similar Potyviruses potentially and their effects on crops.
It has yet to be seen on whether transferring this gene sequence to other species will have similar outcomes, but one can hope.
The fight of scientific excavation continues.
Photo CCs: Maize farm-Tanzania from Wikimedia Commons