TRANSGENIC enhancement of salinity tolerance in wheat could potentially help Australian farmers reclaim part of the $2 billion deficit they face each year, due to salinity problems in over 69 per cent of arable land.
Focusing on the phenomenon of ‘respiration’, UWA PhD student at the ARC Centre of Excellence in Plant Energy Biology Mr Richard Jacoby believes ‘respiration’ holds the answers to many stress responses in plants, including that of ionic stress.
“Under salinity, large stores of carbon are diverted from photosynthesis and growth into a process called respiration, which helps the plant deal with problems created by salinity,” he says.
“By looking at the literature on salt-tolerant species such as mangroves, it appears that 'adaptors' appear to minimise salt damage thanks to protective biochemical processes, while plants that fall into the ‘excluders’ category reject salt back out.
“We have identified two antioxidant proteins produced by adaptors during respiration – alternative oxidase (AOX) and a ‘beefed up’ version of superoxide dismutase (MnSOD) – and these proteins act like bodyguards in the cell and minimise the spread of damage from the salt.”
Chief Investigator Winthrop Professor Harvey Millar says transgenic experiments would ascertain whether transgenic wheat lines with higher levels of MnSOD and AOX would outperform control lines on saline land under field conditions.
However, he says “salinity tolerance is a notoriously complex phenomenon that has been linked to thousands of genes and we think the addition of one single gene would have little agronomic benefit.”
“So the main challenge now is to dig deeper into the wheat proteome (sum of all the proteins) where hundreds of very important proteins are only present at low levels in the cell.”
W/Prof Millar says unlike DNA or RNA, there are no PCR-like methods to amplify the amount of these proteins, which means they must spend a large amount of time enriching the mitochondrial proteome (proteins found in the mitochondria), by separating intact mitochondria from the thousands of other cellular proteins.
“Even then, we have only identified around 300 wheat mitochondrial proteins, although we suspect there are over 1000,” says W/Prof Millar.
W/Prof Millar and Mr Jacoby understand that transgenic crops face a difficult path to market, for both social and regulatory reasons.
“The key aspect of our findings is that they can be applied using conventional breeding, as we are discovering genes that exist in wheat varieties, where crossing procedures are already established.”
Mr Jacoby says the research is at an early stage and will take a few more years to find out all proteins that can be measured. He says the sequencing of the wheat genome, currently underway by some Australian researchers and internationally, will be of considerable help.