Abstract
BackgroundWheat grain avenin-like proteins (ALPs) belong to a recently discovered class of wheat grain storage protein. ALPs in wheat grains not only have beneficial effects on dough quality but also display antifungal activities, which is a novel observation for wheat storage proteins. Previous studies have shown that ALPs are likely present in the albumin/globulin fractions of total protein extract from wheat flour. However, the accumulation characteristics of these ALPs in the mature wheat grain remains unknown.ResultsIn the present study, a total of 13 ALPs homologs were isolated and characterized in the albumin/globulin fractions of the wheat protein extract. A combination of multiple techniques including RP-HPLC, SDS-PAGE, MALDI-TOF and peptide sequencing were used for accurate separation and identification of individual ALP homolog. The C-terminal TaALP-by-4AL/7DS, TaALP-by-4AL/7AS/7DS, TaALP-bx/4AL/7AS/7DS, TaALP-ay-7DS, TaALP-ay-4AL, TaALP-ax-4AL, TaALP-ax-7AS, and TaALP-ax-7DS, were separated as individual protein bands from wheat flour for the first time. These unique ALPs peptides were mapped to the latest wheat genome assembly in the IWGSC database. The characteristic defence related proteins present in albumin and globulin fractions, such as protein disulfide-isomerase (PDI), grain softness protein (GSP), alpha-amylase inhibitors (AAIs) and endogenous alpha-amylase/subtilisin inhibitor were also found to co-segregate with these identified ALPs, avenin-3 and α-gliadins. The molecular weight range and the electrophoresis segregation properties of ALPs were characterised in comparison with the proteins containing the tryp_alpha_amyl domain (PF00234) and the gliadin domain (PF13016), which play a role in plant immunity and grain quality. We examined the phylogenetic relationships of the AAIs, GSP, avenin-3, α-gliadins and ALPs, based on the alignment of their functional domains. MALDI-TOF profiling indicated the occurrence of certain post-translations modifications (PTMs) in some ALP subunits.ConclusionsWe reported for the first time the complete profiling of ALPs present in the albumin/globulin fractions of wheat grain protein extracts. We concluded that majority of the ALPs homologs are expressed in wheat grains. We found clear evidence of PTMs in several ALPs peptides. The identification of both gliadin domain (PF13016) and Tryp_alpha_amyl domain (PF00234) in the mature forms of ALPs highlighted the multiple functional properties of ALPs in grain quality and disease resistance.
Highlights
Wheat grain avenin-like proteins (ALPs) belong to a recently discovered class of wheat grain storage protein
Classification of ALPs and other albumin and globulin proteins ALPs contain a signal peptide and two protein domains: Gliadin domain (PF13016) and Tryp_alpha_amyl domain (PF00234), which are present in other albumin and globulin proteins, such as the avenin-3, gliadins, grain softness protein (GSP) and amylase inhibitors (AAIs)
We identified most ALPs in the albumin/ globulin fraction rather than the glutenin and gliadin fractions, which are dominated with typical gluten proteins
Summary
Wheat grain avenin-like proteins (ALPs) belong to a recently discovered class of wheat grain storage protein. Juhász et al [8] established a new reference map for immunostimulatory wheat grain prolamin and non-prolamin proteins based on the new IWGSC bread wheat reference genome sequence, RefSeq v1.0. Among these re-defined seed-borne allergens, the hydrophobic-seed domain-containing proteins show characteristics of antifungal properties, including cortical cell delineating protein [9], glycine-rich protein [10] and proline-rich protein [11]. The extraction, quantification and identification of the complete profile of these individual prolamin proteins in wheat posed a challenge, due to the complexity of the wheat flour proteins
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
