Researchers at the UK-based John Innes Centre have found the elusive genetic element controlling the elongated grains and glumes of a wheat variety identified by botanist Carl Linnaeus over 250 years ago. 

The findings relating to Polish wheat, Triticum polonicum, could translate into genetic improvements and productivity in the field.

Wheat in bread, pasta and other forms is a vital energy and protein source. Each grain is nestled within the glumes and other leaf-like organs called lemma and palea, which affect the grain’s final size, shape and weight.

Gene characteristics
Characterized by Linnaeus in 1762, Polish wheat has long grains, glumes and lemmas. Previous research showed that all these characteristics were controlled by one gene, but which one among wheat’s complex genome has been unclear.

Researchers used genomic, field-based, and biotechnological approaches to identify the responsible molecular component as VRT-A2, a member of the MADS-box family of transcription factors that act as genetic switches controlling protein synthesis.

Dr. Nikolai Adamski, first author of the paper, says the results highlight how changes in the expression of transcription factors can impact critical agronomic traits for significant crops such as wheat. 

“Our goal is to use this knowledge to help deliver genetic solutions to improve wheat productivity.”

Growth stages
The team identified a small sequence rearrangement leading to misexpression of VRT-A2 in different tissues at several growth stages of wheat. This variation is responsible for the longer grains and floral organs found in Polish wheat.

Introducing the VRT-A2 version from Polish wheat into a UK bread wheat cultivar led to higher grain weight, size and test weight (a measure of the grain density) but did not increase yield in UK environments.

Commenting on the broader significance of the research, Professor Cristobal Uauy, a group leader at the John Innes Centre, adds: “Every day, each person on the planet eats the grains of the equivalent of 50 wheat plants. With a growing demand for wheat, and against the backdro of climate change, we must increase wheat production sustainably.”

“As part of this effort, understanding the genetic control of grain size and weight is extremely relevant to deliver genetic solutions,” he explains. 

Wheat rearrangement 
The experiments also revealed a strong positive correlation between VRT-A2 expression levels and the magnitude of its effects on grain length and floral organ size.

In Polish wheat, the VRT-A2 gene carries a small rearrangement in its first intron – a genetic sequence that does not code for protein but is essential for regulating the gene’s expression. The researchers suggest that this rearrangement was caused by errors in DNA repair following a double-strand break.

Next, the research team aims to understand how the VRT-A2 expression pattern is controlled by the sequence rearrangement in the gene’s first intron.

They also plan to identify the downstream genes affected by VRT-A2 misexpression.

In Polish wheat, the VRT-A2 gene carries a small rearrangement in its first intron – a genetic sequence that does not code for protein but is essential for regulating the gene’s expression.
In recent months, wheat has been at the forefront of research studies. 

In November 2019, John Innes Centre researchers developed an open-source reproducible Agrobacterium-mediated transformation system for the spring wheat cultivar “Fielder” (Triticum aestivum L.). While transformation efficiency for wheat has languished around 5 percent for many years despite its global importance, this system can yield efficiencies of up to 25 percent of those generally achieved using comparable systems, according to the researchers.

Meanwhile in April 2020, a study comparing historic and modern wheat varieties showed an increase in dietary fiber and a decrease in acrylamide, indicating that white bread is not as unhealthy as it has often been portrayed. Published in the journal Scientific Reports, researchers reported “a great deal of variation between years” – suggesting that environmental conditions such as rain or drought also affect nutritional quality, but that this is small when compared to the effect of the variety. 

Last November, an international research collaboration, including scientists from the University of Adelaide’s Waite Research Institute, unlocked new genetic variation in wheat and barley. At the time, the researchers said this could be a significant boost for the global effort in breeding higher-yielding wheat and barley varieties

Meanwhile in October, Arista Cereal Technologies and Limagrain marketed a new wheat ingredient in Europe, following reports that its fiber-rich wheat ingredient performed well in its first year in US retail stores

In August, Arcadia Biosciences revealed its latest move in the commercialization of wheat ingredients across Europe with a collaboration with GoodMills Innovation. The partnership focuses on the broad health and nutritional benefits of Arcadia’s portfolio of improved wheats.