Research investigates barley protein's role in growth regulation during high temperatures

Research, led by Professor Dabing Zhang from the Waite and Shanghai Jiao Tong University's Joint Lab for Plant Science and Breeding, found that under high temperatures barley protein HvMADS1 regulated the number of flowers generated on each spike - the reproductive structure from which grain is harvested.

Through the use of genome editing and crop transformation techniques, researchers were able to generate mutant plants that did not have HvMADS1 present, stopping the function that results in barley spikes remaining unbranched in high temperatures.

The new plants had a branched structure and therefore had more flowers at high ambient temperatures.

Lead author of a study into the research published in Nature Plants, Waite Research Institute's Dr Gang Li said the removal of the protein was tested on three barley varieties - a United Kingdom barley variety Golden Promise, the malting variety Vlamingh and an advanced Australian spring barley breeding line WI4330.

"This protein is evident in the germplasm of all barley varieties," Dr Li said.

"We investigated a variation database that includes more than 20,000 varieties and this protein existed in all varieties."

Dr Li said HvMASD1 was very conserved and also present in other plants and crops, including rice, and was an important protein.

While defects of flower organ development were evident in other plants where the protein was removed, they observed normal development in the barley without it.

Dr Li said while there was no change in barley plant height or leaf between the base varieties and those without HvMADS1, and flowering time and fertility were quite similar, there was a significant impact on tiller number.

"We totally eliminated the protein HvMADS1 in some barley varieties," he said.

"We focused on the spike, but this gene also had an effect on tiller number.

"When it came to the number of tillers there was an increase present in our mutant (without HvMADS1) compared to the regular plant.

"For example, in one single plant with the protein the average tiller number was six and producing an average of 180 seeds per plant, while the average tiller number in our mutant plants was eight to ten, resulting in an average of 250 seeds/plant.

"The seed size was smaller, but not significant, in the plants without the protein, both at high and normal temperatures, and we believe that the protein also regulates the seeds' development during barley reproduction."

LEAD author of a study on HvMADS1, Dr Gang Li, said while it had long been presumed that environmental cues like temperature were responsible for the differences in biological structures evident in cereals, the mechanisms behind those structural changes were largely unknown.

"Cereal crops are worth more than $12 billion to the Australian economy," he said.

"Genes that control the amount of grain produced per plant under higher temperatures are attractive targets for breeders and researchers, particularly in the face of changing environmental conditions."

Co-author and Waite Research Institute deputy director Associate Professor Matthew Tucker said the research revealed the new role the protein family played in responding to thermal change and directing the composition of flowers on a stem.

"With short to medium temperature rises predicted globally, plant scientists and breeders have an enormous challenge ahead of them to generate crop yields needed to feed growing populations in higher temperatures," he said.

"By having a better understanding of the genes underpinning desirable plant traits in response to temperature, scientists can offer insights into breeding climate-smart plants to sustain productivity."

The researchers said this work may provide new avenues for crop breeding potential to overcome the compromise between heat tolerance and high yield.

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