Loss-of-function mutations in novel triacylglycerol lipase genes are associated with low rancidity in pearl millet flour

Abstract

Commercialization and utilization of pearl millet (Pennisetum glaucum L.) by consumers and processing industry is constrained due to rapid onset of rancidity in its milled flour. We studied the underlying biochemical and molecular mechanisms to flour rancidity in contrasting inbreds under 21-day accelerated storage. Rapid triacylglycerol (TAG) decrease was accompanied by free fatty acid (FFA) increase in high rancidity genotype compared to the low rancidity line, that maintained lower FFA and high TAG levels, besides lower headspace aldehydes. DNA sequence polymorphisms observed in two lipase genes revealed loss-of-function mutations that were functionally confirmed in yeast system. We outline a direct mechanism for mutations in these key TAG lipases in pearl millet and the protection of TAG and fatty acids from hydrolytic and oxidative rancidity respectively,. Natural variation in the PgTAGLip1 and PgTAGLip2 genes may be selected through marker assisted breeding or by precision genetics methods to develop hybrids with improved flour shelf life.

Applications and prospects of genome editing in plant fatty acid and triacylglycerol biosynthesis

“…The putative lipases were identified in rice and pearl millet ( Bhunia et al, 2021 ; Kumar et al, 2021 ). In pearl millet, PgTAGLip1 and PgTAGLip2 polymorphisms were identified to cause loss-of-function mutation in an inbred line that low rancidity ( Aher et al, 2022 ). Therefore, the disruption of lipase by CRISPR/Cas9 in rice or pear millet may be a key point in avoiding rancidity ( Bhunia et al, 2021 ; Kumar et al, 2021 ).…”

CRISPR for accelerating genetic gains in under-utilized crops of the drylands: Progress and prospects

“…A collaborative effort between the CGIAR and industry outlined a direct mechanism for hydrolytic and oxidative rancidity in millet flour, allelic variation two candidate lipase genes, Pg TAGLip1 and Pg TAGLip2 were identified, that correlated with the rancidity profile, confirming their function. Mutations in these key TAG lipases in pearl millet have potential in protection of lipids from TAG hydrolysis and fatty acid oxidation, leading to a reduction in off-flavour volatiles ( Aher et al, 2022 ). In addition, since pearl millet has abundance of unsaturated fatty acids (>78%) representing the reactive center that produces odor-active volatiles, major markers for lipid oxidation ( Sharma, 2015 ).…”