Sequence variation and haplotypes of lipoxygenase gene LOX-1 in the Australian barley varieties

Abstract

BackgroundLipoxygenases are a family of enzymes which catalyse the hydroperoxidation of polyunsaturated fatty acids with a cis, cis-1,4-pentadiene to form conjugated hydroperoxydienes. Lipoxygenase-1 (LOX-1) in barley worsens the flavour and foam stability of beer. It has become a major selection criteria for malting quality in the last few years.ResultsLipoxygenase activity was investigated in 41 Australian barley cultivars and advanced breeding lines released since the 1950s; the cultivars differed markedly, ranging from 22.3 to 46.5 U/g. The structural gene and its promoter of lipoxygenase-1 were sequenced from the barley varieties representing different levels of LOX. Based on the analysis of nucleotide and deduced amino acid sequences, two major haplotypes were identified. Barley varieties with lower LOX were classified into three categories based on their pedigrees and sequence variations in the structural gene: (1) barley varieties derived from Canadian varieties with the pre-harvest sprouting susceptible allele, (2) Skiff and Hindmarsh with unique haplotype in the structural gene, and (3) Gairdner and Onslow with an unknown mechanism.ConclusionLipoxygenase activity has been reduced in the malting barley cultivars in the last 60 years although it is only recognized as a malting quality trait recently. There are clear haplotypes of the lipoxygenase structual gene. The polymorphisms detected in the structural gene can be used to design molecular markers for selection of low LOX haplotype. Other mechanisms also existed for controlling lipoxygenase activity. The results suggest that it is possible to develop barley varieties with lower LOX by combination of low LOX-1 haplotype and other trans-regulation factors.

Green Malt for a Green Future – Feasibility and Challenges of Brewing Using Freshly Germinated (Unkilned) Malt: A Review

“…Apart from being a dominant consumer of heat and electricity, the kilning process has many beneficial impacts on malt quality, which must be considered if it is to be omitted. These include reduction of lipoxygenase activity 19,[38][39][40][41][42][43][44][45][46] , regulation of S-methyl methionine (SMM) levels [47][48][49][50][51][52] , facilitating rootlet removal, diminishing unwanted "raw grain" characteristics 14 and, most importantly, developing the characteristic colour and flavours which malt imparts to beer. Furthermore, green malt, having a moisture content between 38-46%, is unstable and cannot be stored for prolonged periods.…”

Optimization of kilning progress for equilibrating multiple parameters that strictly affect malt flavour and sensory evaluation

“…Longer withering time results in lower water content in malt, which could also accelerate the denaturation of the LOX enzyme (21)(22)(23)(24)(25). treatment from a high temperature than time.…”

“…The LOX enzyme is a thermosensitive oxidation-reduction enzyme, the denaturation and inactivation of which are more easily generated by thermal treatment from a high temperature than time. Longer withering time results in lower water content in malt, which could also accelerate the denaturation of the LOX enzyme (21)(22)(23)(24)(25). Generally, 0.5-3% activity remained after the kilning course.…”

“…treatment from a high temperature than time. Longer withering time results in lower water content in malt, which could also accelerate the denaturation of the LOX enzyme (21)(22)(23)(24)(25). Generally, 0.5-3% activity remained after the kilning course.…”

Functional Characterization of9-/13-LOXsin Rice and Silencing Their Expressions to Improve Grain Qualities

“…In barley, a LOX-1 deficient line “ DaikeiLM1 ” is gained from “ Karl M2 ” through sodium azide treatment [ 9 ]. This mutated line can effectively improve flavor stability in beer [ 10 ]. In rice, the absence of sLOX3 in the seeds of “ DawDam ” results in less stale flavor [ 11 ].…”