Researchers crack the code: First availability of psyllium genome sequence

17 Feb 2023 --- Researchers have constructed the reference genome for psyllium husk, a popular fiber supplement. The researchers, from the University of Adelaide, Australia, note that many attempts have been made to develop higher-yielding varieties, but conventional breeding approaches have yet to improve seed or psyllium production significantly.

NutritionInsight talked with three of the study’s authors about how the availability of this genome may help accelerate plant breeding programs and improve husk quantity and quality. 

“The key strength of this study is the first availability of a high-quality genome sequence for this plant species,” says Dr. Lina Herliana, lead author of the study. 

Professor Rachel Burton adds, “We hope that researchers and breeders will use this resource as a tool to help them better understand the biology of how psyllium is made by the Plantago ovata plant and to support breeding advances for agronomic traits such as disease resistance and yield parameters.”

Next steps
According to the study, published in Scientific reports, Psyllium husk is used as a dietary fiber, stabilizer and ingredient in gluten-free foods. Herliana explains that access to husk’s genome will allow breeders to develop better markers for specific traits.

“Some of these could be perfect markers based on DNA sequence differences, such as single nucleotide polymorphisms (SNPs) in genes expressed at variable levels under stress, for example, drought or disease.” 

Plant breeding programs can use the psyllium genome sequence to develop new cultivars. “The genome sequence will allow our group to pinpoint better the important genes functioning in complex processes,” notes Burton, “like seed development, mucilage biosynthesis, capsule development and seed shattering.” 

She adds that other groups may use it to help unravel essential traits like plant height, disease resistance and the number of seed heads.

“All these traits can ultimately affect psyllium yield, which then flows on to its supply and use in food and pharmaceuticals.”  

The development of the genome “will also support lab-based experiments to understand better how carbohydrates in plants are constructed so we can tailor them for food and pharmaceutical uses,” according to Dr. James Cowley. 

Need for the genome 
Burton notes that the genome will pave the way for improvements to the quality and quantity of psyllium crops.

“We predict the availability of this reference genome will lead to the development of new cultivars with higher yields that are more adaptable to environmental conditions,” says Herliana. “This will stabilize the production of psyllium products and seed or husk price.”

The researchers explain that psyllium is sensitive to environmental changes that may threaten the supply chain and increase its global price.

Cowley adds that psyllium “may have other novel uses that could be developed if a reliable supply of high-quality psyllium could be established.”

Psyllium potential 
Burton explains that the researchers extracted and sequenced the deoxyribonucleic acid (DNA) from leaf tissue to construct the chromosome-level reference genome for Plantago ovata. They used ribonucleic acid (RNA) from other parts of the plant to predict the function of the plant’s genes. 

The researchers combined the data generated at the University of Adelaide with publicly available RNA sequencing data to predict the gene models. 

The researchers extracted DNA from leaf tissue and RNA from other parts of the plant. However, Herliana warns there is still a need to experimentally verify the Plantago ovata genes’ functions in the wet lab. “Gene functions are assigned based on their similarities to known genes in other species, using the latest bioinformatics tools and the new genome.” 

“Psyllium is increasingly being used as a key hydrocolloid to replace gluten in foods such as bread as it can mimic gluten’s properties without being an issue for some consumers,” says Cowley. 

NutritionInsight previously reported on a gluten-free bread containing psyllium and chickpea flour. Psyllium was used to increase fiber content and the resulting product had high nutritious values, according to a study. 

“It can also be used in other baked goods and acts as a valuable source of bulking dietary fiber,” adds Cowley. “In the pharmaceutical industry, psyllium is finding increasing utility as a drug disintegrant.”

Consumers are increasingly aware of fiber’s health benefits, but daily fiber consumption is insufficient. Companies are attempting to bridge this fiber gap with reformulation. 

By Jolanda van Hal