Growth & Development

Sunshine makes oats healthier

Study discovers the importance of light conditions and biosynthetic regulation of mixed-linkage glucan in oats.

Soluble fibres in cereals have many health benefits such as prevention of obesity, high serum cholesterol and heart diseases. Mixed-linkage glucan (MLG) can be mainly found in the grass family (Poaceae) in the cell walls. They also provide important attributes to cereal products (e.g. breadmaking performance, thickening ability). 

Dr Bing Wu and four colleagues from the Chinese Academy of Agricultural Sciences investigated the genes responsible for MLG synthesis in oats under different light conditions. The researchers identified cellulose synthase-like (Csl) gene families involved in MLG production and found that MLG concentration rose from 0.07% to 1.06% under high light intensity. This is the first time scientists have uncovered the regulation of MLG production in oats as previous research focused on barleys. 

Drs Jing Zhang, Bing Wu and colleagues grew the oat cultivar Xiayoumai, known for high glucan content (>6%), under dark, low (80 µmol/m2/s) and high (300 µmol/m2/s) light conditions for two days. Leaf, stem, root and developing seed samples were taken to extract RNA and DNA for gene structure analysis and gene expression patterns. MLG concentration was also measured and the localisation was verified by immunoelectron microscopy.

Image: Canva

Genes involved in the MLG biosynthesis were orthologous to cellulose synthase-like (Csl) gene families and were named AsCslF3, AsCslF4, AsCslF6, AsCslF8, AsCslF9, AsCslH and AsCslJ. These genes were expressed differently in different plant tissues. The genes AsCslF6, AsCslF8, AsCslF3 and AsCslF9 were 8- to 10-fold higher expression level in the light than in the dark. MLG content indeed increased under light growth conditions and under high light intensity, the cell wall of oat was fully filled with MLG molecules.

Micrograph showing leaf cross-sections
Transmission electron micrographs of leaf cross sections from (A) dark-grown and (C) high light intensity-grown oat leaves (CW, cell wall; PM, plasma membrane) showing immunogold labeling with (1,3;1,4)-β-D-glucan-specific (MLG) antibody. Source: Zhang et al. 2020

Whilst high MLG content is undesirable for the barley processing industry (e.g. malting, brewing), it is desirable for oats due to health benefits. For the first time, scientists have identified genes involved in MLG production and found that these genes are expressed more under high light conditions. 

“[T]his may also explain why the MLG level in grains grown in Spain (hot and higher light intensity) was higher than in Scotland (cooler and lower light intensity)”, Zhang, Wu and colleagues wrote.

“Considering MLG content determines much of the value of oat crop to the producer, our findings will provide new insights and speculations to produce better quality oats.”

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