Scientists crack one of broadacre cropping’s most sought genetic secrets
Queensland, Australia
February 2, 2023
30 years of research at The University of Queensland and the Department of Agriculture and Fisheries (DAF) has culminated in gene discoveries that allow breeders to better protect cereal crops from water scarcity.
The discoveries culminated in key findings made by the Australian Research Council (ARC) funded project Cereal blueprints for a water-limited world, led by Professor Andrew Borrell in collaboration with researchers from the Queensland Alliance for Agriculture and Food Innovation (QAAFI) and DAF.
Professor Andrew Borrell
Researchers spent decades investigating a trait known as stay-green, where some sorghum lines maintained green leaves for longer under dry conditions, leading to higher grain yield.
“We have now uncovered genetic clues that allow a major step change in our ability to breed for drought adaptation,” Professor Borrell said.
“With stay-green, we see very specific physiological and morphological changes both in the way the plants grow above the ground and below in the roots.
“We have systematically characterised the trait, starting with overall plant biology and most recently, digging down to the gene level.”
The research centred on the discovery of nine members of the PIN gene family that genetically align with chromosome regions implicated in mediating stay-green characteristics.
These PIN genes act in concert to regulate auxin hormone levels, which in turn, trigger biological mechanisms that produce drought adaptations.
This cascade of physiological changes then keep leaves green for longer through three main mechanisms.
They reduce the plant’s need for water before flowering by producing a smaller canopy, increase the plant’s supply of water by producing deeper roots and increase the efficiency in the way the plant uses water.
Importantly, the team dissected the role of individual PIN genes and identified three that create unprecedented opportunities to design the drought adaptation characteristics of commercially grown sorghum.
Dissecting PIN gene function involved resource development that created plants that either over-express the PIN genes via genetic transformation or knock out the genes via CRISPR-Cas9 technology.
These genetic resources were primarily developed by QAAFI’s Dr Karen Massel and characterised by Dr Albert Wong, as part of Professor Borrell’s ARC Discovery project.
“We discovered that various combinations of PIN genes can be used to change the root, canopy, leaf anatomy, photosynthesis and panicle characteristics of sorghum crops in ways that affect drought resilience,” Professor Borrell says.
“That means that PIN genes are now part of a toolkit to custom-make crops suited to dry environments and to a changing climate.”
The work began in the early 1990s when Professor Borrell was issued a challenge by DAF’s legendary breeder the late Dr Bob Henzell to find out why stay-green sorghum increased yield under drought.
“Bob told me that stay-green increased sorghum yield under drought, but he added that he didn’t know why,” Professor Borrell said.
“He then issued me the challenge, as a physiologist, to find out why.
“These discoveries are truly a team effort,” said Professor Borrell.
Genetic similarities with other cereal crops – including wheat and barley – mean these genetic findings have implications for making the Australian grains industry more drought resilient.
Work to understand the impact of PIN genes in other cereals is already underway.
Early research on the physiological basis of stay-green was funded by the Grains Research and Development Corporation (GRDC), with the more recent PIN gene research funded by the Australian Research Council (ARC), UQ and DAF.
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